Abstract
Background.
Autologous hematopoietic stem cell transplantation (AHSCT) is associated with sexual dysfunction and hypogonadism. Androgens are associated with sexual function in healthy men, but the role of estrogens is less well-known, and the association of these sex steroids with sexual function during AHSCT has not been characterized.
Objectives.
The purpose of this study was to determine the predictive value of sex hormones before and acutely after AHSCT on sexual function recovery.
Materials and Methods.
We examined sex hormones and self-reported sexual function before (PRE) and one month post-AHSCT (MONTH1; n=19), and sexual function again one-year post-AHSCT in men (YEAR1; n=15).
Results.
Sexual function decreased from PRE to MONTH1 (p≤0.05) with no differences between PRE and YEAR1. Erectile dysfunction was prevalent at PRE (68.4%) and increased at MONTH1 (100%; p≤0.05) but was not different between PRE and YEAR1 (60.0%). From PRE to MONTH1, total testosterone (TT), dihydrotestosterone (DHT), follicle-stimulating hormone, and sex-hormone binding globulin (SHBG) increased (p≤0.02) while estradiol (p≤0.026) and estrone decreased (p≤0.001). MONTH1 TT and DHT were associated with sexual function at MONTH1, while PRE SHBG, MONTH1 estradiol, and change in estrone predicted sexual function at YEAR1.
Discussion.
Sexual dysfunction is very prevalent prior to AHSCT and is transiently and severely worsened acutely after. AHSCT induces acute decreases in total and free estrogens, with SHBG increases leading to increases in total androgens, without changes in free androgens.
Conclusion.
Androgens and estrogens are both adversely affected by AHSCT but may predict sexual dysfunction in this population. This supports the premise that estrogen impacts sexual function independent from androgens and that steroid hormones are associated with acute changes in sexual function in this setting. Larger, controlled trials with long-term sex hormone assessment will need to confirm the association between early changes in estrogens and long-term sexual function recovery.
Keywords: hematopoietic stem cell transplantation, sexual function, erectile dysfunction, sexual desire, estrogen, testosterone
Introduction
Hematopoietic stem cell transplantation (HSCT) is a standard treatment option for a range of hematologic malignancies. Advances in transplantation techniques and supportive care measures have significantly improved survival for HSCT recipients (1). However, complications stemming from this intensive treatment such as sexual dysfunction and endocrine complications often result in poor quality-of-life for survivors (2). The negative impact of HSCT on sexual function remains a vital and often overlooked aspect of recovery, despite being one of the most reported short- and long-term complications. While the nadir of sexual function is around six months post-HSCT (3), up to 60% of patients reported at least one sexual problem, including erectile dysfunction or difficulty with intercourse/orgasm, one year after HSCT (4–6), which persisted when reassessed two to three years post-HSCT (4,5). In addition, only 50% of patients reported having a discussion with their healthcare provider about the impact of HSCT on sexual function before or one- and three-years after HSCT (4). Survivors also reported more sexual dysfunction than non-transplant recipient controls five (3) to ten years (7) after HSCT.
Circulating sex-hormones, particularly testosterone, are thought to be directly associated with sexual function in other settings. In otherwise healthy older men with sexual dysfunction, low vitality or impaired mobility and low total testosterone (Testosterone Trials), total testosterone (TT) and free testosterone (FT) levels were directly correlated with sexual desire, erectile function, and sexual activity (8). In a community-based cohort of men aged 40–79 without hypogonadism (European Male Ageing Study), TT and FT levels were each directly correlated with sexual function (9). In another cohort of men over 70 years of age (Concord Health and Ageing in Men Project), declines in TT and FT over a two-year follow-up were associated with declines in sexual activity and desire, but not erectile function (10). Similarly, erectile function and/or sexual desire decreased in otherwise healthy men after endogenous testosterone suppression induced with a gonadotropin-releasing hormone agonist (11) or with dihydrotestosterone (DHT) (12). In addition, sexual function was reportedly responsive to testosterone replacement therapy when men with low libido and low TT were given testosterone vs. placebo for one year (13). In that study, testosterone treatment improved sexual desire and sexual activity compared to placebo and these improvements were directly associated with increases in TT and FT and also with estradiol (13).
Estrogens have also been identified as contributing to the maintenance of sexual function in men, including sexual desire (11,12) and erectile function (10,11) independently from the effects of testosterone. In men, estrogens are synthesized through aromatization of testosterone taking place in testes and other tissues including adipose, brain, skin, and bone (14). Despite this purported importance of estrogen on sexual function in men, the impact of HSCT on estrogen levels in men has not been reported to date. This may be partly due to the difficulty in characterizing such a role since estrogen levels tend to move in parallel with testosterone in men unless paired with pharmacologic manipulation, such as a gonadotropin-releasing hormone agonist or DHT (11,12). In addition, not all studies measured estrogens by mass spectrometry, the only method that can accurately measure the low levels of estradiol and estrone present in men.
In the setting of HSCT, abnormal levels of sex hormones have been reported in association with sexual dysfunction over numerous years following HSCT. In autologous HSCT (AHSCT) recipients, 14/16 (88%) men displayed elevated follicle-stimulating hormone (FSH) and 6/16 (38%) displayed low TT three years post-HSCT; TT was indirectly correlated with reduced or absence of libido (15). However, this report did not evaluate hormone levels or sexual function before AHSCT, or in the acute period after AHSCT, and did not evaluate free testosterone or estrogens. The role of acute sex hormone changes on sexual function in AHSCT recipients is uncharacterized. Determining the predictive value of these parameters on longer-term recovery of sexual function may help identify patients who are at risk of prolonged or more complicated recovery and potentially develop therapies to alter the course of these complications. The purpose of this study was to examine changes in sexual function and sex hormones (androgens, estrogens, and precursor steroids), acutely after AHSCT, and to determine whether sex hormone levels are predictive of sexual dysfunction over time. We hypothesized that low testosterone and estradiol prior to AHSCT and a decrease in their levels acutely after AHSCT are independently associated with reduced sexual function after AHSCT in men, both in the short- and long-term.
Methods
Study Participants
Patients with confirmed myeloma or lymphoma planning treatment with AHSCT at the Veterans Affairs Puget Sound Health Care System (VAPSHCS) BMTU in Seattle, WA, USA, were eligible. Patients who declined participation were excluded. The protocol was approved by the VAPSHCS Institutional Review Board and the Research and Development Committee and was conducted in compliance with the Declarations of Helsinki and its amendments and the International Conference on Harmonization Guideline for Good Clinical Practices. Recruitment took place between February 2017 and July 2018.
Study Design and Protocol
Study measurements were assessed at baseline (PRE: after enrollment into the BMTU but prior to chemomobilization), one-month after AHSCT (MONTH1), and one-year after AHSCT (YEAR1). At PRE and MONTH1, patients reported to VAPSHCS in the morning after fasting overnight. A plasma sample was obtained before 10AM to measure circulating hormone and cytokine markers followed by assessment of total body fat mass (FM) via dual-energy X-ray absorptiometry (Hologic Inc., Marlborough, MA, USA) and patient-reported sexual function via the International Index of Erectile Function (IIEF) which measures the following five domains: Erectile Function, Orgasmic Function, Sexual Desire, Intercourse Satisfaction, and Overall Satisfaction, in addition to overall IIEF Total (16). Erectile Function and Sexual Desire domains are most related to testosterone and estradiol and are presented as the main sexual function outcomes of this manuscript (8). Patient-reported depression and emotional well-being were also assessed via the Anderson Symptom Assessment Score (ASAS) (17) and Functional Assessment of Chronic Illness Therapy (FACIT) (18), respectively. Participants were mailed the IIEF, ASAS, and FACIT approximately one-year after AHSCT and with instructions to return the forms to VAPSHCS by mail once completed (YEAR1).
Biomarker Analysis
Plasma sex hormones including 17-hydroxypregnenolone (ng/mL), 17-hydroxyprogesterone (ng/mL), androstenedione (ng/mL), androsterone (ng/mL), dehydroepiandrosterone (ng/mL), DHT (ng/mL), pregnenolone (ng/mL), progesterone (ng/mL), and total testosterone (TT; ng/mL) were analyzed via liquid-chromatography tandem mass spectroscopy and sex-hormone binding globulin (SHBG; nmol/L) was measured with the Quantikine SHBG Immunoassay (R&D Systems, Minneapolis, MN, USA) as previously reported (19). The reference ranges for TT and calculated free testosterone (cFT), defined as the 2.5 – 97.5th percentile for healthy men aged 18 to 50 years, were 2.42 – 9.84 ng/ml and 5.75 – 16.81 ng/dl, respectively. Free testosterone, DHT, estradiol, and estrone were calculated with theoretical association constants (20). In addition, patients’ clinically available albumin levels were extracted from chart review, using the value assessed at the closest date to PRE or MONTH1 within a 1-week window, and used for calculation of free hormone concentrations.
Plasma concentrations of estradiol and estrone were quantified after hexane/ethyl acetate extraction by liquid chromatography-tandem mass spectrometry, using a dansyl chloride derivatization method on an AB Sciex 6500 QTRAP tandem quadrupole mass spectrometer with positive electrospray ionization (ESI+; Foster City, CA). The lower limit of quantification was 1.2 pg/ml for both estradiol and estrone. The intra-assay co-efficient of variation was 3.97% for estradiol and 7.35% for estrone. The reference ranges for estradiol and estrone, defined as the 2.5–97.5th percentile for healthy men aged 18 to 50 years, were 14.2–46.9 pg/ml and 16.9–60.3 pg/ml, respectively. Free estradiol and estrone were calculated with theoretical association constants (20). In addition, patients’ clinically available albumin levels were extracted from chart review, using the value assessed at the closest date to PRE or MONTH1 within a 1-week window, and used for calculation of free hormone concentrations.
Follicle-stimulating hormone (FSH) in plasma was analyzed by ELISA Kit from Enzo Life Sciences, Inc (Cat# ENZ-Kit 108–0001; Farmingdale, NY, USA). A protocol provided by the manufacturer was used for this assay. The specificity of this assay is 100% and the limit of detection is ≤ 0.5 mLU/ml. Inflammatory cytokines in plasma were detected by V-PLEX Human Pro-inflammatory Panel 1 (Cat# N05049 A-1) from Meso Scale Discovery (Rockville, MD, USA). The V-PLEX kit contains (interleukin) IL-1β, IL-6, and (tumor necrosis factor) TNF spotted in each well as sandwich immunoassays. A protocol provided by the manufacturer was used for this assay. The V-PLEX plate was read on MesoScale Discovery Sector Imager and the data was analyzed by Discovery Workbench v4.0. software.
Statistical Analysis
SPSS v18 (SPSS, Inc., Chicago, IL) was used for statistical analysis, data are expressed as mean (95% CI) or n (%). The change in fat mass and sex hormones was calculated as MONTH1 level – PRE level. Comparison across time points was analyzed using Repeated-Measures ANOVA for IIEF, ASAS, and FACIT and using paired t-test for biomarkers. Comparison across time points for categorical data were performed using the Fisher’s exact test or Chi-squared test. Statistical significance was 2-sided, α ≤ 0.05. Multivariate regression was used to determine predictors of sexual function at PRE, MONTH1, and YEAR1.
Results
Study Participants
Twenty patients participated in PRE assessment [evaluation of patient-reported outcomes, hormone levels, and fat mass], 19 participated in MONTH1 assessment [evaluation of patient-reported outcomes, and hormone levels]; we were only able to assess FM on 12 patients at MONTH1. Fifteen participated in YEAR1 assessment [evaluation of patient-reported outcomes only] (Figure 1). Data are presented as mean (95% CI) or number, n (%).
Figure 1.
PRE, baseline visit; MONTH1, one-month follow-up visit; YEAR1 one-year follow-up visit.
Baseline demographics, diagnosis, and recent treatment exposure is provided in Table 1 for the 19 patients who participated in both PRE and MONTH1. There were 41 (36, 46) days between PRE and AHSCT, 26 (23, 29) days between AHSCT and MONTH1, and 397 (363, 431) days between AHSCT and YEAR1. Cumulative glucocorticoid exposure between PRE and MONTH1 was 120.8 (86.7, 155.0) mg (dexamethasone equivalents); all patients received at least 8 mg. Between PRE and AHSCT, eight (42.1%) patients received 3500 (2000, 5000) mg cyclophosphamide only and eleven (57.9%) received 6850 (3700, 8600) mg of cyclophosphamide plus 1140 (425, 1300) mg of etoposide for chemomobilization. For the conditioning regimens, patients with multiple myeloma received 350 (250, 435) mg of melphalan and patients with lymphoma received BEAM (carmustine, etoposide, cytarabine, and melphalan) or mini-BEAM regimens: 582.5 (440, 645) mg of carmustine, 3080 (1200, 3450) mg of cytarabine, 3080 (1200, 3450) mg of etoposide, and 272.5 (200, 290) mg of melphalan. One patient (5%) also received 900 cGy of localized radiotherapy to a foot lesion. All patients are male.
Table 1.
Baseline Characteristics
| n = 19 | Mean (95% CI) |
|---|---|
|
| |
| Age (yr) | 63 (57, 69) |
| BMI (kg/m2) | 30.0 (27.6, 32.5) |
| HCT-CI range (0–7) a | 3.1 (2.0, 4.2) |
|
| |
| Ethnicity | n (%) |
|
| |
| White Non-Hispanic | 12 (63.2) |
| White Hispanic | 1 (5.3) |
| Black | 3 (15.8) |
| Asian/Pacific Islander | 1 (5.3) |
| Mixed | 2 (10.4) |
|
| |
| Diagnosis | |
|
| |
| Multiple Myeloma | 14 (73.7) |
| T-cell Lymphoma | 1 (5.3) |
| Hodgkin Lymphoma | 1 (5.3) |
| B-cell non-Hodgkin Lymphoma | 3 (15.7) |
|
| |
| Recent chemotherapy exposure (y) b | |
|
| |
| Alkylating Agents | 2 (10.5) |
| Topoisomerase Inhibitors | 1 (5.3) |
| Immunomodulators | 8 (42.1) |
| Proteasome Inhibitors | 6 (31.6) |
| None | 9 (47.4) |
|
| |
| Prior Glucocorticoid exposure (y) c | 9 (47.4) |
|
| |
| Relationship Status | |
|
| |
| Married | 11 (57.9) |
| Single | 8 (42.1) |
Range for this cohort;
within one month prior to enrollment in Bone Marrow Transplant Unit (BMTU);
within three months prior to enrollment in BMTU; BMI, body mass index; HCT-CI, hematopoietic cell transplant comorbidity index; y, yes. Enrollment into the study occurred within a few days after enrollment into BMTU.
Patient-Reported Outcomes
On average, patient-reported Erectile Function and Sexual Desire significantly decreased from PRE to MONTH1 and then significantly increased from MONTH1 to YEAR1 (Figure 2, A–B); there were no differences between PRE and YEAR1. The same changes were observed between PRE and MONTH1 for Orgasmic Function, Intercourse Satisfaction, and Total IIEF score (Figure 3). Presence of erectile dysfunction was indicated by the Erectile Function domain score where ≤ 24 represents any degree [mild (13 – 24), moderate (8 – 12), or severe (0 – 7)] of erectile dysfunction (16,21,22). The proportion of patients with any degree of erectile dysfunction significantly increased from PRE (13/19, 68.4%) to MONTH1 (19/19, 100%; p ≤ 0.05) and significantly decreased from MONTH1 to YEAR1 (9/15, 60.0%; p ≤ 0.05), but was not different between PRE and YEAR1; the Fisher’s exact 2-sided p-value was 0.005 for the comparison across time points. Seven (36.8%) of 19 patients reported a clinically important decrease in Erectile Function score from PRE to MONTH1 [≥ −4 points (22)]. Nine (60.0%) of 15 patients reported a clinically important increase in Erectile Function score from MONTH1 to YEAR1 (≥ +4 points). In addition, PRE Erectile Function score was significantly higher for patients with clinically important decreases from PRE to MONTH1 [20.0 (14.0, 26.0)] than patients with less than a 4-point decrease [2.5 (1.3, 3.7); p < 0.001, data not shown]. Neither depression nor emotional well-being were different between Pre and MONTH1 or between PRE and YEAR1; emotional well-being significantly decreased from MONTH1 to YEAR1 (Figure 2, C–D).
Figure 2.
Box and whisker plots for (A) Erectile Function from International Index of Erectile Function (IIEF), (B) Sexual Desire from IIEF, (C) Depression from ASAS, and (D) Emotional Well-Being from FACIT. ED, erectile dysfunction; PRE, baseline visit; MONTH1, follow-up 1; YEAR1, follow-up 2; x = mean; mid-line = median. *p≤0.05.
Figure 3.
Box and whisker plots for (A) Orgasmic Function from International Index of Erectile Function (IIEF), (B) Intercourse Satisfaction from IIEF, (C) Overall Satisfaction from IIEF, and (D) IIEF Total. PRE, baseline visit; MONTH1, follow-up 1; YEAR1, follow-up 2; x = mean; mid-line = median. *p≤0.05.
Sex Hormones
At PRE and MONTH1, we assessed plasma: 1) FSH to evaluate pituitary response, 2) total and free androgens (testosterone and DHT) and estrogens (estradiol and estrone) as the primary sex hormones modulating sexual function, and 3) SHBG as a hormone carrier known to be altered in cancer (23,24). On average, TT, total DHT, SHBG, and FSH significantly increased from PRE to MONTH1, although cFT and calculated free DHT (cFDHT) did not change (Table 2). Total and calculated free estradiol and estrone decreased significantly from PRE to MONTH1 (Figure 3, A–B). Changes in precursor steroid hormones from PRE to MONTH1 include increases in 17-hydroxyprogesterone and androstenedione (Table 3). Patients with clinically important decreases in Erectile Function score from PRE to MONTH1 displayed significantly smaller changes in total estradiol [0.9 (−4.6, 6.4) vs. −7.6 (−12.5, −2.8); p = 0.016], calculated free estradiol [−0.03 (−0.17, 0.10) vs. −0.26 (−0.40, −0.13); p = 0.012], total estrone [−3.2 (−9.2, 2.9) vs. −11.3 (−17.5, −5.1); p = 0.046], and calculated free estrone [−0.12 (−0.36, 0.13) vs. −0.54 (−0.78, −0.29); p = 0.013], and al larger change in 17-hydroxyprogesterone [0.60 (0.31, 0.89) vs. 0.21 (0.04, 0.39); p = 0.021] compared to patients with less than a 4-point decrease in Erectile Function score (data not shown). There were no other differences in hormone changes between patients with or without a clinically important decrease in Erectile Function score from PRE to MONTH1. There were no differences at PRE in absolute hormone values between patients with or without a clinically important decrease in Erectile Function score; however, cFDHT [2.4 (1.7, 3.1) vs. 1.6 (1.0, 2.2); p = 0.04] and 17-hydroxyprogesterone [1.3 (1.0, 1.7) vs. 0.8 (0.6, 1.1); p = 0.022] were higher at MONTH1 for patients with a clinically important decrease in Erectile Function score compared to those without a clinically important decrease.
Table 2.
Plasma hormone and cytokine levels and acute changes after AHSCT
| Mean (95% CI) | PRE n = 19 | MONTH1 n = 18 | Paired t-test | Change |
|---|---|---|---|---|
| TT (ng/mL) | 3.47 (2.58, 4.36) | 4.70 (3.66, 5.74) | 0.009 | 1.23 (0.34, 2.11) |
| cFT (ng/dL) | 6.67 (5.16, 8.39) | 6.54 (4.97, 8.17) | 0.61 | −0.38 (−1.91, 1.15) |
| DHT (ng/mL) | 0.26 (0.19, 0.32) | 0.34 (0.27, 0.41) | 0.02 | 0.06 (0.00, 0.13) |
| cFDHT (pg/mL) | 2.28 (1.73, 2.83) | 1.90 (1.44, 2.36) | 0.094 | −0.42 (−0.91, 0.08) |
| SHBG (nmol/L) | 34.9 (27.9, 41.9) | 70.2 (55.1, 85.4) | <0.001 | 35.3 (23.9, 46.8) |
| FSH (IUL) | 15.6 (5.4, 25.7) | 19.5 (9.7, 29.3) | 0.001 | 3.94 (1.95, 5.94) |
| IL-6 (pg/mL) | 2.28 (0.58, 3.99) | 2.63 (1.48, 3.77) | 0.69 | 0.34 (−2.13, 1.44) |
| TNF (pg/mL) | 2.86 (1.76, 3.96) | 3.51 (2.64, 4.38) | 0.21 | 0.65 (−1.69, 0.39) |
TT, total testosterone; cFT, calculated free testosterone; DHT, dihydrotestosterone; cFDHT, calculated free dihydrotestosterone; SHBG, sex-hormone binding globulin; FSH, follicle-stimulating hormone; IL, interleukin; TNF, tumor necrosis factor; change = MONTH1 value – PRE value.
Table 3.
Other mediators of steroidogenesis
| Mean (95% CI) (n = 19) | PRE | MONTH1 | Paired t-test | Change |
|---|---|---|---|---|
| 17-Hydroxypregnenolone (ng/mL) | 1.09 (0.71, 1.46) | 1.05 (0.70, 1.39) | 0.88 | −0.04 (−0.51, 0.43) |
| 17-Hydroxyprogesterone (ng/mL) | 0.67 (0.51, 0.83) | 1.02 (0.79, 1.25) | <.001 | 0.35 (0.19, 0.52) |
| Androstenedione (ng/mL) | 0.54 (0.40, 0.67) | 1.21 (0.89, 1.53) | .001 | 0.67 (0.33, 1.01) |
| Androsterone (ng/mL) | 0.11 (0.09, 0.12) | 0.14 (0.11, 0.17) | 0.06 | 0.03 (0.00, 0.06) |
| DHEA (ng/mL) | 0.98 (0.72, 1.23) | 0.93 (0.64, 1.22) | 0.70 | 0.0 (−0.30, 0.21) |
| Pregnenolone (ng/mL) | 0.43 (0.33, 0.54) | 0.40 (0.27, 0.53) | 0.52 | −0.03 (−0.13, 0.07) |
| Progesterone (ng/mL) | 0.05 (0.04, 0.07) | 0.07 (0.06, 0.09) | 0.056 | 0.02 (0.00, 0.04) |
PRE, baseline visit; MONTH1, follow-up 1; change = MONTH1 value – PRE value.
There was no difference between PRE and MONTH1 in proportion of patients with low TT [< 2.42 ng/mL: 7 (36.8%) vs. 3 (15.8%) Fischer’s exact 2-sided p = 0.27] or cFT [< 5.75 ng/dL: 11/19 (57.9%) vs. 8/18 (44.4%), Fischer’s exact 2-sided p = 0.52] or in proportion of patients with hypoestrogenemia by estradiol levels [< 14.2 pg/mL: 5 (26.3%) vs. 8 (50.0%), Fischer’s exact 2-sided p = 0.50]. There was a trend for a greater proportion of patients with low estrone at MONTH1 compared to PRE [< 16.9 pg/mL: 2 (10.5%) vs. 8 (50.0%), Fischer’s exact 2-sided p = 0.06]. No patients were hyperestrogenemic by estradiol (> 46.9 pg/mL) or estrone (> 60.3 pg/mL) at either PRE or MONTH1 (reference ranges for TT, cFT, estradiol, and estrone are provided in Materials and Methods). Albumin was significantly higher at PRE [4.2 (4.1, 4.3) g/dL] than MONTH1 [3.8 (3.6, 4.0) g/dL; p<0.001].
Fat Mass and Inflammation
We measured FM by dual-energy x-ray absorptiometry and circulating cytokines [IL-6, IL-1β, and TNF] from plasma samples. Whole body FM significantly decreased from PRE to MONTH1 [−0.90 (−1.65, −0.15) kg; p = 0.02] as we previously reported in this cohort (25). BMI did not significantly change from PRE to MONTH1 [−0.8 (−2.2, 0.5) kg/m2; p=0.23]. FM was not correlated with total or free estradiol or estrone and PRE or MONTH1 (data not shown). There was also no correlation between change in FM with change in SHBG, change in any T variable (including total T, bioavailable T, free T, total DHT, or free DHT), or change in any estrogen variable (including total or free estrone or estradiol), data not shown here. There was no difference between PRE and MONTH1 in IL-6 or TNF (Table 2), neither was there any difference between PRE and MONTH1 in proportion of patients with detectable IL-1β [10 (52.6%) vs. 7 (36.8%) Fischer’s exact 2-sided p = 0.26]. We also extracted liver function enzyme (aspartate transaminase and alanine transaminase) levels from patients’ medical charts assessed within one week of PRE or MONTH1 visits and analyzed for change; levels were not different between PRE and MONTH1 (p > 0.05, data not shown). At PRE, two (10.5%) patients displayed a level above the upper limit of normal for at least one liver function enzyme; this was observed in four (21.1%) patients at MONTH1.
Multivariate Regression for Predicting Sexual Function at PRE
The following conditional variables were included in models determining predictors of sexual function at PRE: age, diagnosis (dichotomous variable: multiple myeloma or lymphoma), FM, chemotherapy exposure in the prior month before enrollment into the Bone Marrow Transplant Unit (BMTU) as a dichotomous variable (y/n), corticosteroid exposure in prior 3 months before enrollment into the BMTU (dichotomous variable: y/n), PRE total and free testosterone, DHT, estradiol, and estrone, PRE SHBG, PRE FSH, and PRE cytokines (IL-1β was a dichotomous variable: above or below the limit of detection).
Age was a negative predictor of Sexual Desire (Table 4); there were no other significant predictors of Sexual Desire or Erectile Function at PRE.
Table 4.
Significant predictors of sexual function before and after autologous HSCT using multivariate regression
| Dependent Variable | R2 | Significant Predictors | Unsth. B (95% CI) | p-value | |
|---|---|---|---|---|---|
|
| |||||
| PRE (n = 19) | Erectile Function | None | |||
| Sexual Desire | 0.34 | Age | −0.13 (−0.21, −0.04) | 0.008 | |
|
| |||||
| MONTH1 (n = 16) | Erectile Function | 0.83 | MONTH1 cFT (pg/mL) # of days post-AHSCT |
0.03 (0.02, 0.05) 0.09 (0.01, 0.17) |
<0.001 0.038 |
| Sexual Desire | 0.63 | MONTH1 cFT (pg/mL) MONTH1 DHT (ng/mL) |
0.06 (0.03, 0.08) −9.29 (−17.51, −1.01) |
0.001 0.03 |
|
|
| |||||
| YEAR1 (n = 12) | Erectile Function | 0.55 | PRE SHBG (nmol/L) | −0.51 (−0.84, −0.19) | 0.006 |
| Sexual Desire | 0.77 | MONTH1 estradiol (pg/mL) Change in estrone (pg/mL) |
13.0 (6.9, 19.0) 0.10 (0.00, 0.20) |
0.001 0.046 |
|
PRE, baseline visit; MONTH1, follow-up 1; YEAR1, follow-up 2; cFT, calculated free testosterone; AHSCT, autologous hematopoietic stem cell transplant; DHT, dihydrotestosterone; SHBG, sex-hormone binding globulin; change = MONTH1 value – PRE value.
Multivariate Regression for Predicting Sexual Function at MONTH1
The following conditional variables were included in models determining predictors of sexual function at MONTH1: age at PRE, diagnosis (dichotomous variable: multiple myeloma or lymphoma), PRE and MONTH1 FM, change (MONTH1 – PRE) in FM, AHSCT preparatory chemo class (dichotomous variable: cyclophosphamide alone or cyclophosphamide plus etoposide), cumulative corticosteroid exposure between PRE and MONTH1 (dexamethasone mg equivalents), number of days post-AHSCT for MONTH1, PRE and MONTH1 total and free testosterone, DHT, estradiol, and estrone, PRE and MONTH1 SHBG, change in total and free testosterone, DHT, estradiol, and estrone, change in SHBG, and PRE and MONTH1 cytokines (IL-1β was a dichotomous variable: above or below the limit of detection).
MONTH1 cFT and number of days post-AHSCT at MONTH1 were predictors of Erectile Function, while MONTH1 cFT and MONTH1 DHT were predictors of Sexual Desire (Table 4; there were no other significant predictors of Sexual Desire or Erectile Function at MONTH1.
Multivariate Regression for Predicting Sexual Function at YEAR1
The following conditional variables were included in models determining predictors of sexual function at YEAR1: age at PRE, diagnosis (dichotomous variable: multiple myeloma or lymphoma), PRE and MONTH1 FM, change (MONTH1 – PRE) in FM, AHSCT preparatory chemo class (dichotomous variable: cyclophosphamide alone or cyclophosphamide plus etoposide), cumulative corticosteroid exposure between PRE and MONTH1 (dexamethasone mg equivalents), number of days post-AHSCT for YEAR1, PRE and MONTH1 total and free testosterone, DHT, estradiol, and estrone, PRE and MONTH1 SHBG, change in total and free testosterone, DHT, estradiol, and estrone, change in SHBG, and PRE and MONTH1 cytokines (IL-1β was a dichotomous variable: above or below the limit of detection).
PRE SHBG was a predictor of Erectile Function, while MONTH1 estradiol and change (MONTH1 – PRE) in estrone were predictors of Sexual Desire (Table 4); there were no other significant predictors of Sexual Desire or Erectile Function at YEAR1.
Discussion
Here we report that sexual dysfunction is very prevalent in this population prior to and is transiently and severely worsened acutely after AHSCT, but similar to baseline levels one year later. We also report the novel finding of decreases in total and free estradiol and estrone, associated with increases in SHBG, TT, and DHT, without changes in cFT and cFDHT from baseline to one-month post-AHSCT. After adjusting for fat mass, diagnosis, and age in multivariate regression, cFT and DHT levels assessed one-month post-AHSCT and number of days post-AHSCT were predictors of sexual function assessed one-month post-AHSCT. Alternatively, SHBG assessed at baseline, estradiol assessed one-month post-AHSCT, and the change in estrone from baseline to one-month post-AHSCT were predictors of sexual function assessed one-year post-AHSCT.
Our current findings suggest that the effect of AHSCT on sexual function in men is significant, and very prevalent acutely, but transient over a one-year period (Figures 2–3). Nevertheless, we report a high prevalence of sexual dysfunction prior to beginning the AHSCT treatment regimen. This prevalence likely results from longer-term history of exposure to treatments aimed at achieving remission status, which is required to become a candidate for AHSCT in addition to other factors such as age. This information is clinically useful for anticipating treatment of AHSCT side effects and managing patients’ expectations of side effect magnitude and duration. Our observations are similar to other reports of persistent sexual dysfunction one year after HSCT. Lee et al. reported a 29% prevalence of any “sexual difficulty” using a 5-point Likert scale one year after HSCT (5). This prevalence was the same for allogeneic (79 total) or autologous (69 total) transplant recipients, each group was approximately 50% men; the prevalence prior to HSCT was not reported (5).
Similarly, Humphreys et al. reported 36% prevalence of erectile dysfunction and 55% prevalence of low libido out of 42 men one year after allogeneic HSCT using questions adapted from the Sexual History Form and the Sexual Problems Measure (4). These were slightly higher than their reported prevalence of 26% erectile dysfunction and 45% with low libido out of 131 men assessed prior to transplant (4). Noerskov et al. observed that 55% of 38 men reported at least one “sexual problem” at least half of the time one year after allogeneic HSCT using the Sexual Function Questionnaire (6). This was increased from their reported 30% prevalence of 83 men assessed prior to transplant (6). While we did not observe a significant increase in sexual dysfunction from PRE to YEAR1 in the current study, we do report similar incidence of sexual dysfunction at the one-year post-HSCT time point as these previous reports.
The relatively high prevalence of sexual dysfunction prior to transplant in the current study compared to that of other reports may be due to the heterogeneity across studies in the tool used to capture this outcome. It may also be due to the variation in average age of the cohorts which was 10 – 20 years older in the current study, which could also contribute to the high prevalence of testosterone deficiency (biochemical hypogonadism) in the current study; although, testosterone deficiency was not reported in these other studies (4–6). According to the longitudinal Massachusetts Male Ageing Study, approximately 50% of men with a mean age of 62.7 years reported at least minimal erectile dysfunction (26). Considering the mean age in current cohort was also 63 years, the prevalence of erectile dysfunction reported here (68%) may not be that surprising, given our patients’ characteristics and comorbidities. Larger studies including non-cancer controls would be needed to determine if the prevalence of erectile dysfunction is significantly higher in this population. With the exception of the Sexual Function Questionnaire (27), these other tools have not been validated in the HSCT population and may not be suitable to use for assessing the association between sexual function and sex hormones, as was carried out via the IIEF in the current study (8).
Here we observed an increase in TT, SHBG, and DHT, with no change in cFT or cFDHT, acutely after AHSCT. Despite the increases in TT, TT measured at PRE, MONTH1, or the change thereof, were not predictors of the primary sexual function parameters (Erectile Function or Sexual Desire) at any time point. Instead, MONTH1 cFT was associated with MONTH1 Erectile Function and MONTH1 cFT and MONTH1 DHT were both associated with MONTH1 Sexual Desire, which are both symptoms of hypogonadism. This observation highlights this importance of assessing free testosterone, the biologically active fraction of testosterone, which may be more associated with sexual function than TT in this setting. An important factor in determining free hormone levels is SHBG, which is secreted by the liver and is thought to be regulated by factors such as age and fat mass (28–30). While malignancy is likely a contributing factor to the elevated SHBG reported in current study, increases in SHBG have been reported in other settings of cancer (24), and in other chronic, inflammatory conditions (31), so it is unlikely that this is unique to hematologic malignancy or AHSCT. Based on what is known as the “free hormone hypothesis,” these increases are not generally thought to play an active role in modulating the free levels of sex hormones although there is some evidence that SHBG changes can modulate their action by the differential affinity of testosterone and estrogen to SHBG (32). The increases in SHBG observed here likely explain the lack of change in cFT and cFDHT despite the increases in total hormone levels. In addition, despite unchanged cFT (and increased androstenedione), both total and calculated free levels of estradiol and estrone were also decreased one month after AHSCT, which could be due to decreased production, by decreased aromatase activity, or by increased estrogen clearance, for example, by increased conjugation or metabolism. Increases in the steroid precursors androstenedione and 17-hydroxyprogesterone more likely occurred as a result of increases in luteinizing hormone (that unfortunately were not measured here) rather than increases in adrenocorticotropic hormone as other adrenal steroid precursors did not increase. These changes are not likely clinically relevant since they did not correspond to measurable change in free levels of T or DHT, which are historically associated with sexual function (8–10).
Although testosterone is the main circulating sex steroid in men, estrogens have recently been recognized as an important mediator of sexual function in men (11). The main source of estradiol in men is testosterone through aromatization (33); hence, estrogen and testosterone levels typically change in parallel. However, if aromatase activity is decreased, estrogen levels decrease while testosterone does not (Figure 4). The impact of HSCT on estrogen levels in men may be important because estrogen deficiency is associated with osteoporosis (34). Evidence also suggests estrogen deficiency may lead to elevated production of inflammatory cytokines such as IL-1, IL-6, and TNF in the bone marrow which may further complicate the recovery process (34,35). Finkelstein et al. reported that, after administration of a gonadotropin-releasing hormone agonist, sexual desire scores decreased by 13% if estradiol levels were above 10 pg/mL, and decreased by 31% if estradiol levels were below 10 pg/mL (11). In our study, mean estradiol levels remained above 10 pg/mL, but mean sexual desire score still decreased similarly (27%) from 5.7 at PRE to 3.7 at MONTH1 (Figure 2B). The association observed here between early changes in estrogens and SHBG with longer-term sexual function aligns with recent evidence suggesting that estrogens are important determinants of sexual function in men. Interestingly, we also observed that acute estrogen decreases were associated with maintenance of erectile function; however, due to the high prevalence of erectile dysfunction in this cohort prior to AHSCT, we are hesitant to interpret this to mean that decreases in estrogen are beneficial for erectile function. The clinical relevance of these estrogen decreases will need to be determined in future studies where measuring SHBG, estradiol, and estrone may help predict sexual function recovery in AHSCT patients.
Figure 4.
Box and whisker plots for (A) total estradiol and (B) calculated free estradiol. PRE, baseline visit; MONTH1, follow-up 1; x = mean; mid-line = median. *p≤0.05.
Other factors affecting sexual dysfunction and circulating sex hormones in HSCT recipients may include chemotherapy or corticosteroids. Alkylating chemotherapy agents such as cyclophosphamide, which was used to treat patients here, are commonly used in HSCT preparatory regimens and are particularly damaging to gonadal function and can reduce testosterone levels (36,37). Similarly, elevated FSH was reported after cyclophosphamide treatment in patients with nephrotic syndrome (38). Thus, the increase in FSH observed in our study could be due to Sertoli cell dysfunction/impaired spermatogenesis related to cyclophosphamide, which suggests testicular insult and not a hypothalamic/pituitary-mediated mechanism. Corticosteroids are also frequently utilized to mitigate the innate inflammatory and immune response after HSCT and have been associated with reduced testosterone in the setting of inflammatory respiratory disease (39,40). The impact of corticosteroid treatment is most often observed in patients receiving allogeneic HSCT who are at high risk of developing chronic graft-versus-host-disease (37). AHSCT recipients receive limited courses of mild to moderate corticosteroid doses during initial induction chemotherapy and to mitigate inflammation and reduce nausea in the acute time period around the transplant. Additionally, psychological factors such as decreased intimacy or satisfaction with relationship status may also be important contributors.
This study has many strengths and limitations that should be mentioned. Most notably, sex hormone measures were not obtained at YEAR1 due to the fact that the VAPSHCS BMTU is one of only three bone marrow transplant centers in the VA system, and transplant recipients come from across the country for their transplant, and then return to their local VA center for follow-up care approximately one month after AHSCT. Other limitations include the relatively small sample size with significant loss (25%) to follow up at YEAR1, lack of cortisol and adrenocorticotropic hormone measurement to assess the stress of the AHSCT process and hypothalamic-pituitary-adrenal axis, heterogeneity of concomitant medication schemes for myeloma and lymphoma, and restriction of generalizability of results to the Veteran male population. In addition, we attempted to assess luteinizing hormone; however, available assays are validated in serum and we obtained unreliable measures with our plasma samples. The strengths of this study design include the relatively homogeneous sample of AHSCT recipients and state-of-the-art steroid measurements by liquid chromatography-tandem mass spectrometry. Furthermore, this is the first study to investigate estrogens in men undergoing HSCT.
Conclusions
Sexual dysfunction is very prevalent prior to AHSCT and is transiently and severely worsened acutely after AHSCT. AHSCT also induces acute decreases in total and free estrogens, with SHBG increases leading to increases in total androgens, without changes in free androgens. Circulating cFT and DHT assessed one-month post-AHSCT and number of days post-AHSCT were predictors of sexual function assessed one-month post-AHSCT. Alternatively, SHBG assessed at baseline, estradiol assessed one-month post-AHSCT, and the change in estrone from baseline to one-month post-AHSCT were predictors of sexual function assessed one-year post-AHSCT. These observations support the premise that estrogen plays a role in sexual function independent to that of androgens and that steroid hormones are associated with acute changes in sexual function in the AHSCT setting. Larger, controlled trials with long-term sex hormone assessment will be needed to confirm the association between early changes in estrogens and long-term sexual function recovery.
Figure 5.
Schematic displaying the conversion to testosterone and estrogen from common precursors. HSD = hydroxysteroid dehydrogenase. Schematic representing the production of testosterones and estrogens from androstenedione. Converting enzymes are displayed in dashed boxes with arrows indicating direction of conversion. Testosterone is also produced from conversion of androstenediol by 3β-HSD, not shown here.
Acknowledgments
This material is the result of work supported with resources and the use of facilities at the VAPSHCS and the National Institutes of Health National Institute of Diabetes and Digestive and Kidney Diseases funded Nutrition Obesity Research Center (DK035816) and Diabetes Research Center (P30 DK017047) at the University of Washington. We also thank the VAPSHCS R&D Mass Spectrometry Assay Core. J.M.G. receives research support from the VA (BX002807), the Congressionally Directed Medical Research Program (CDMRP PC170059), and from the National Institutes of Health (R01CA239208, R01AG061558). L.J.A receives support from the University of Washington (T32 DK 007247–42) and the VA (IK2 RX003245).
Funding: This research received no external funding.
Footnotes
Disclosures: The authors declare no conflict of interest.
References
- 1.McDonald GB, Sandmaier BM, Mielcarek M, et al. Survival, Nonrelapse Mortality, and Relapse-Related Mortality After Allogeneic Hematopoietic Cell Transplantation: Comparing 2003–2007 Versus 2013–2017 Cohorts. Annals of internal medicine. Feb 18 2020;172(4):229–239. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Bhatia S. Long-term health impacts of hematopoietic stem cell transplantation inform recommendations for follow-up. Expert review of hematology. Aug 2011;4(4):437–452; quiz 453–434. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Syrjala KL, Kurland BF, Abrams JR, Sanders JE, Heiman JR. Sexual function changes during the 5 years after high-dose treatment and hematopoietic cell transplantation for malignancy, with case-matched controls at 5 years. Blood. Feb 1 2008;111(3):989–996. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Humphreys CT, Tallman B, Altmaier EM, Barnette V. Sexual functioning in patients undergoing bone marrow transplantation: a longitudinal study. Bone marrow transplantation. Apr 2007;39(8):491–496. [DOI] [PubMed] [Google Scholar]
- 5.Lee SJ, Fairclough D, Parsons SK, et al. Recovery after stem-cell transplantation for hematologic diseases. Journal of clinical oncology : official journal of the American Society of Clinical Oncology. Jan 1 2001;19(1):242–252. [DOI] [PubMed] [Google Scholar]
- 6.Noerskov KH, Schjodt I, Syrjala KL, Jarden M. Sexual function 1-year after allogeneic hematopoietic stem cell transplantation. Bone marrow transplantation. Jun 2016;51(6):833–840. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Syrjala KL, Langer SL, Abrams JR, Storer BE, Martin PJ. Late effects of hematopoietic cell transplantation among 10-year adult survivors compared with case-matched controls. Journal of clinical oncology : official journal of the American Society of Clinical Oncology. Sep 20 2005;23(27):6596–6606. [DOI] [PubMed] [Google Scholar]
- 8.Cunningham GR, Stephens-Shields AJ, Rosen RC, et al. Association of sex hormones with sexual function, vitality, and physical function of symptomatic older men with low testosterone levels at baseline in the testosterone trials. The Journal of clinical endocrinology and metabolism. Mar 2015;100(3):1146–1155. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9.O’Connor DB, Lee DM, Corona G, et al. The relationships between sex hormones and sexual function in middle-aged and older European men. The Journal of clinical endocrinology and metabolism. Oct 2011;96(10):E1577–1587. [DOI] [PubMed] [Google Scholar]
- 10.Hsu B, Cumming RG, Blyth FM, et al. The longitudinal relationship of sexual function and androgen status in older men: the Concord Health and Ageing in Men Project. The Journal of clinical endocrinology and metabolism. Apr 2015;100(4):1350–1358. [DOI] [PubMed] [Google Scholar]
- 11.Finkelstein JS, Lee H, Burnett-Bowie SA, et al. Gonadal steroids and body composition, strength, and sexual function in men. The New England journal of medicine. Sep 12 2013;369(11):1011–1022. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12.Sartorius GA, Ly LP, Handelsman DJ. Male sexual function can be maintained without aromatization: randomized placebo-controlled trial of dihydrotestosterone (DHT) in healthy, older men for 24 months. The journal of sexual medicine. Oct 2014;11(10):2562–2570. [DOI] [PubMed] [Google Scholar]
- 13.Cunningham GR, Stephens-Shields AJ, Rosen RC, et al. Testosterone Treatment and Sexual Function in Older Men With Low Testosterone Levels. The Journal of clinical endocrinology and metabolism. Aug 2016;101(8):3096–3104. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Vermeulen A, Kaufman JM, Goemaere S, van Pottelberg I. Estradiol in elderly men. The aging male : the official journal of the International Society for the Study of the Aging Male. Jun 2002;5(2):98–102. [PubMed] [Google Scholar]
- 15.Schimmer AD, Ali V, Stewart AK, Imrie K, Keating A. Male sexual function after autologous blood or marrow transplantation. Biology of blood and marrow transplantation : journal of the American Society for Blood and Marrow Transplantation. 2001;7(5):279–283. [DOI] [PubMed] [Google Scholar]
- 16.Rosen RC, Riley A, Wagner G, Osterloh IH, Kirkpatrick J, Mishra A. The international index of erectile function (IIEF): a multidimensional scale for assessment of erectile dysfunction. Urology. Jun 1997;49(6):822–830. [DOI] [PubMed] [Google Scholar]
- 17.Palmer JL, Fisch MJ. Association between symptom distress and survival in outpatients seen in a palliative care cancer center. Journal of pain and symptom management. Jun 2005;29(6):565–571. [DOI] [PubMed] [Google Scholar]
- 18.Butt Z, Lai JS, Rao D, Heinemann AW, Bill A, Cella D. Measurement of fatigue in cancer, stroke, and HIV using the Functional Assessment of Chronic Illness Therapy - Fatigue (FACIT-F) scale. Journal of psychosomatic research. Jan 2013;74(1):64–68. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19.Harrington LB, Marck BT, Wiggins KL, et al. Cross-sectional association of endogenous steroid hormone, sex hormone-binding globulin, and precursor steroid levels with hemostatic factor levels in postmenopausal women. Journal of thrombosis and haemostasis : JTH. Jan 2017;15(1):80–90. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20.Mazer NA. A novel spreadsheet method for calculating the free serum concentrations of testosterone, dihydrotestosterone, estradiol, estrone and cortisol: with illustrative examples from male and female populations. Steroids. Jun 2009;74(6):512–519. [DOI] [PubMed] [Google Scholar]
- 21.Derby CA, Araujo AB, Johannes CB, Feldman HA, McKinlay JB. Measurement of erectile dysfunction in population-based studies: the use of a single question self-assessment in the Massachusetts Male Aging Study. International journal of impotence research. Aug 2000;12(4):197–204. [DOI] [PubMed] [Google Scholar]
- 22.Rosen RC, Cappelleri JC, Gendrano N 3rd. The International Index of Erectile Function (IIEF): a state-of-the-science review. International journal of impotence research. Aug 2002;14(4):226–244. [DOI] [PubMed] [Google Scholar]
- 23.Burney BO, Hayes TG, Smiechowska J, et al. Low testosterone levels and increased inflammatory markers in patients with cancer and relationship with cachexia. The Journal of clinical endocrinology and metabolism. May 2012;97(5):E700–709. [DOI] [PubMed] [Google Scholar]
- 24.Garcia JM, Li H, Mann D, et al. Hypogonadism in male patients with cancer. Cancer. Jun 15 2006;106(12):2583–2591. [DOI] [PubMed] [Google Scholar]
- 25.Anderson LJ, Yin C, Burciaga R, et al. Assessing Cachexia Acutely after Autologous Stem Cell Transplant. Cancers. Sep 4 2019;11(9). [DOI] [PMC free article] [PubMed] [Google Scholar]
- 26.Feldman HA, Longcope C, Derby CA, et al. Age trends in the level of serum testosterone and other hormones in middle-aged men: longitudinal results from the Massachusetts male aging study. The Journal of clinical endocrinology and metabolism. Feb 2002;87(2):589–598. [DOI] [PubMed] [Google Scholar]
- 27.Syrjala KL, Schroeder TC, Abrams JR, et al. Sexual function measurement and outcomes in cancer survivors and matched controls. J Sex Res. Aug 2000;37(3):213–225. [Google Scholar]
- 28.Liu PY, Beilin J, Meier C, et al. Age-related changes in serum testosterone and sex hormone binding globulin in Australian men: longitudinal analyses of two geographically separate regional cohorts. The Journal of clinical endocrinology and metabolism. Sep 2007;92(9):3599–3603. [DOI] [PubMed] [Google Scholar]
- 29.Simo R, Saez-Lopez C, Barbosa-Desongles A, Hernandez C, Selva DM. Novel insights in SHBG regulation and clinical implications. Trends in endocrinology and metabolism: TEM. Jul 2015;26(7):376–383. [DOI] [PubMed] [Google Scholar]
- 30.Zhou SJ, Zhao MJ, Yang YH, et al. Age-related changes in serum reproductive hormone levels and prevalence of androgen deficiency in Chinese community-dwelling middle-aged and aging men: Two cross-sectional studies in the same population. Medicine. Jan 2020;99(1):e18605. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 31.Pena Dias J, Haberlen SA, Dobs AS, et al. Longitudinal Changes in Sex Hormone-Binding Globulin in Men With HIV. Journal of acquired immune deficiency syndromes. Aug15 2021;87(5):1178–1186. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 32.Laurent MR, Hammond GL, Blokland M, et al. Sex hormone-binding globulin regulation of androgen bioactivity in vivo: validation of the free hormone hypothesis. Scientific reports. Oct 17 2016;6:35539. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 33.Longcope C, Kato T, Horton R. Conversion of blood androgens to estrogens in normal adult men and women. The Journal of clinical investigation. Dec 1969;48(12):2191–2201. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 34.Estrogen Pacifici R., cytokines, and pathogenesis of postmenopausal osteoporosis. Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research. Aug 1996;11(8):1043–1051. [DOI] [PubMed] [Google Scholar]
- 35.Feng X, McDonald JM. Disorders of Bone Remodeling. Annu Rev Pathol-Mech. 2011;6:121–145. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 36.Lee SJ, Schover LR, Partridge AH, et al. American Society of Clinical Oncology recommendations on fertility preservation in cancer patients. Journal of clinical oncology : official journal of the American Society of Clinical Oncology. Jun 20 2006;24(18):2917–2931. [DOI] [PubMed] [Google Scholar]
- 37.Yi JC, Syrjala KL. Sexuality after hematopoietic stem cell transplantation. Cancer journal. Jan–Feb 2009;15(1):57–64. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 38.Masala A, Faedda R, Alagna S, et al. Use of testosterone to prevent cyclophosphamide-induced azoospermia. Annals of internal medicine. Feb 15 1997;126(4):292–295. [DOI] [PubMed] [Google Scholar]
- 39.Kamischke A, Kemper DE, Castel MA, et al. Testosterone levels in men with chronic obstructive pulmonary disease with or without glucocorticoid therapy. The European respiratory journal. Jan 1998;11(1):41–45. [DOI] [PubMed] [Google Scholar]
- 40.Morrison D, Capewell S, Reynolds SP, et al. Testosterone levels during systemic and inhaled corticosteroid therapy. Respiratory medicine. Oct 1994;88(9):659–663. [DOI] [PubMed] [Google Scholar]