Abstract
To investigate the impact of preoperative serum follicle-stimulating hormone (FSH) levels on the probability of testicular sperm retrieval, we conducted a study of nonobstructive azoospermic (NOA) men with different testicular volumes (TVs) who underwent microdissection testicular sperm extraction (micro-TESE). A total of 177 NOA patients undergoing micro-TESE for the first time from April 2019 to November 2022 in Shenzhen Zhongshan Obstetrics and Gynecology Hospital (formerly Shenzhen Zhongshan Urology Hospital, Shenzhen, China) were retrospectively reviewed. The subjects were divided into four groups based on average TV quartiles. Serum hormone levels in each TV group were compared between positive and negative sperm retrieval subgroups. Overall sperm retrieval rate was 57.6%. FSH levels (median [interquartile range]) were higher in the positive sperm retrieval subgroup compared with the negative outcome subgroup when average TV was <5 ml (first quartile [Q1: TV <3 ml]: 43.32 [17.92] IU l−1 vs 32.95 [18.56] IU l−1, P = 0.048; second quartile [Q2: 3 ml ≤ TV <5 ml]: 31.31 [15.37] IU l−1 vs 25.59 [18.40] IU l−1, P = 0.042). Elevated serum FSH levels were associated with successful micro-TESE sperm retrieval in NOA men whose average TVs were <5 ml (adjusted odds ratio [OR]: 1.06 per unit increase; 95% confidence interval [CI]: 1.01–1.11; P = 0.011). In men with TVs ≥5 ml, larger TVs were associated with lower odds of sperm retrieval (adjusted OR: 0.84 per 1 ml increase; 95% CI: 0.71–0.98; P = 0.029). In conclusion, elevated serum FSH levels were associated with positive sperm retrieval in micro-TESE in NOA men with TVs <5 ml. In men with TV ≥5 ml, increases in average TVs were associated with lower odds of sperm retrieval.
Keywords: follicle-stimulating hormone, male infertility, nonobstructive azoospermia, sperm retrieval, testis
INTRODUCTION
Millions of people of reproductive age are affected by infertility worldwide. Available data estimated that 8%–12% of couples experience infertility globally, and male factors contribute to approximately 50% of infertile populations.1,2 Azoospermia is a medical condition with sperm absent from the ejaculate even after centrifugation. This condition is identified in approximately 1%–2% of the general male population and in 10%–15% of infertile men.3 Nonobstructive azoospermia (NOA), which comprises about 60% of all azoospermic cases,4 occurs when spermatogenesis is impaired. NOA cases commonly result from primary testicular dysfunction (testicular cause) and rarely result from impairment of the hypothalamus or pituitary (pretesticular cause).5 Azoospermia is the most severe form of male infertility.6
Microdissection testicular sperm extraction (micro-TESE) combined with intracytoplasmic sperm injection (ICSI) is currently a recommended and effective treatment for NOA men.7 Because of the intrinsic testicular impairment of spermatogenesis in NOA patients, the success rate of conventional sperm retrieval is low.8 However, NOA does not mean the total absence of sperm production and up to 60% of men with NOA may have rare spermatogenesis foci in their testes.9 Conventional testicular sperm extraction (cTESE) or testicular sperm aspiration (TESA), which is a surgical procedure that obtains testicular tissue through a small incision and one or multiple random biopsies, does not identify the small sperm-producing areas of the testicle until the tissue has been excised from the NOA patient.10,11 Micro-TESE, a technique first introduced by Schlegel in 1999, differs from the previous sperm retrieval techniques in that sperm-containing regions of the testicle are identified by directly examining the individual seminiferous tubules at 20×–25× power magnification under an operating microscope.10 NOA men present a higher sperm retrieval rate (SRR) in micro-TESE compared with TESA and cTESE.8,11 The increased SRR of micro-TESE might result from the areas with spermatogenesis that can be identified before the removal of testicular tubules during the microsurgical procedure.7,8
However, sperm retrieval from NOA patients is still a challenge for andrologists. The first ICSI procedure using sperm retrieved directly from the testis by cTESE was performed successfully in 1993.12 However, the SRRs of NOA patients, which have been reported at about 20%–45%,13 are significantly lower than those of obstructive azoospermia (OA) patients, whose SRRs are about 100%.14,15 The SRRs of NOA patients with decreased testicular volume (TV) and increased serum follicle-stimulating hormone (FSH) levels are significantly reduced.16,17,18 However, Ramasamy et al.19 found that high serum FSH levels in men with NOA did not affect the success of micro-TESE. Additionally, Bryson et al.20 proved that testicular atrophy was not a contraindication for micro-TESE. In contrast, Kizilkan et al.21 showed that larger testicular size significantly increased micro-TESE SRRs. The meta-analysis found that both TV and serum FSH levels had limited predictive value for predicting the probability of obtaining sperm in micro-TESE.22 Thus, whether micro-TESE has a lower chance of retrieving testicular sperm in NOA patients with elevated serum FSH levels and decreased TV is unclear. Yet, few studies have focused on the influence of serum FSH levels on micro-TESE SRRs in NOA patients with different testicular sizes.
In the present study, the impact of serum FSH levels on the outcome of micro-TESE in NOA patients with different TVs was investigated by (1) comparing preoperative factors such as age, body mass index (BMI), TV, hormonal profiles, and etiology of NOA between patients with positive and negative sperm retrieval outcomes; (2) comparing preoperative serum hormone profiles, including FSH, luteinizing hormone (LH), and testosterone, in NOA men with different micro-TESE sperm retrieval outcomes grouped according to TV; and (3) exploring the association among micro-TESE sperm retrieval outcomes, TV, and preoperative serum hormone levels in NOA patients.
PATIENTS AND METHODS
Patients
We retrospectively reviewed the medical data of men with NOA who underwent micro-TESE for the first time from April 2019 to November 2022 at the Department of Urology in Shenzhen Zhongshan Obstetrics and Gynecology Hospital (formerly Shenzhen Zhongshan Urology Hospital, Shenzhen, China). A total of 194 micro-TESE procedures were included in the present study, and 17 were excluded because serum FSH, LH, or T levels were not recorded (n = 7), the records of serum hormones were vague and lacked definite numerical values (n = 1), BMI values could not be calculated due to missing height data (n = 2), the patients had testicular tumors (n = 2), detailed chromosome microdeletion loci were not recorded (n = 2), and histologic evaluation of the testicular biopsy was not conducted because the tissue was histologically unclear and cell morphology was difficult to examine (n = 3). Finally, 177 patients (22–54 years of age; median: 32 years) were included in this research. The baseline characteristics of the NOA patients were compared between positive (n = 102) and negative (n = 75) sperm retrieval outcomes. The enrolled patients were initially divided into four groups according to average TV quartiles (first quartile [Q1: TV <3 ml]: n = 27; second quartile [Q2: 3 ml ≤ TV <5 ml]: n = 51; third quartile [Q3: 5 ml ≤ TV <8 ml]: n = 55; and forth quartile [Q4: TV ≥8 ml]: n = 44) because the SRR showed statistical significance among these four groups (Supplementary Table 1). The basic characteristics, including age, BMI, smoking habits, hormonal treatment, hormone profiles, and NOA etiology, were compared among average TV quartiles (Supplementary Table 2). Then, the preoperative serum hormone profile (including FSH, LH, and T) in each TV quartile group was compared between the positive and negative sperm retrieval subgroups to further investigate the impact of TV and serum hormones on micro-TESE sperm retrieval outcomes. A flow chart of this study is described in Figure 1.
Supplementary Table 1.
Univariate analysis of sperm retrieval in relation to testicular volume and preoperative serum hormone profiles in men involved in microdissection testicular sperm extraction
| Parameter | Number of patients (n) | Positive sperm retrieval, n (%) | OR (95% CI) | P |
|---|---|---|---|---|
| Quartiles of average bilateral TV (ml) | ||||
| Q1 (TV <3) | 27 | 13 (48.1) | 1.11 (0.43–2.91) | 0.825 |
| Q2 (3≤ TV <5) | 51 | 35 (68.6) | 2.63 (1.14–6.07) | 0.024 |
| Q3 (5≤ TV <8) | 55 | 34 (61.8) | 1.94 (0.87–4.35) | 0.106 |
| Q4 (TV ≥8) | 44 | 20 (45.5) | Reference | NA |
| Quartiles of serum FSH (IU l−1) | ||||
| Q1 (FSH <13.10) | 44 | 24 (54.5) | Reference | NA |
| Q2 (13.10≤ FSH <23.07) | 44 | 23 (52.3) | 0.91 (0.40–2.11) | 0.831 |
| Q3 (23.07≤ FSH <32.95) | 45 | 26 (57.8) | 1.14 (0.49–2.64) | 0.759 |
| Q4 (FSH ≥32.95) | 44 | 29 (65.9) | 1.61 (0.68–3.81) | 0.277 |
| Quartiles of serum LH (IU l−1) | ||||
| Q1 (LH <6.34) | 44 | 23 (52.3) | Reference | NA |
| Q2 (6.34≤ LH <10.02) | 44 | 27 (61.4) | 1.45 (0.62–3.38) | 0.390 |
| Q3 (10.02≤ LH <16.05) | 45 | 25 (55.6) | 1.14 (0.50–2.63) | 0.756 |
| Q4 (LH ≥16.05) | 44 | 27 (61.4) | 1.45 (0.62–3.38) | 0.390 |
| Quartiles of serum testosterone (µg l−1) | ||||
| Q1 (testosterone <1.93) | 40 | 18 (45.0) | 0.45 (0.20–1.03) | 0.058 |
| Q2 (1.93≤ testosterone <3.02) | 36 | 21 (58.3) | 0.77 (0.33–1.81) | 0.554 |
| Q3 (3.02≤ testosterone <4.52) | 42 | 25 (59.5) | 0.81 (0.36–1.84) | 0.618 |
| Q4 (testosterone ≥4.52) | 59 | 38 (64.4) | Reference | NA |
TV: testicular volume; FSH: follicle-stimulating hormone; LH: luteinizing hormone; OR: odds ratio; CI: confidence interval; NA: not applicable
Supplementary Table 2.
Comparison of baseline characteristics among different testicular volume subgroups
| Characteristics | Average of bilateral TV (ml) | P | |||
|---|---|---|---|---|---|
|
| |||||
| TV <3 | 3≤ TV <5 | 5≤ TV <8 | TV ≥8 | ||
| Number of patients | 27 | 51 | 55 | 44 | NA |
| Age (year), median (IQR) | 32 (8) | 31 (3) | 31 (7) | 33 (6) | 0.446# |
| BMI (kg m−2), median (IQR)* | 23.92 (4.88) | 23.25 (4.83) | 23.66 (4.25) | 25.07 (3.58) | 0.032# |
| Smoking habit, n (%) | 6 (22.2) | 8 (15.7) | 8 (14.5) | 6 (13.6) | 0.788b |
| Hormonal therapy, n (%) | 5 (18.5) | 4 (7.8) | 7 (12.7) | 7 (15.9) | 0.520 |
| Hormone profile | |||||
| FSH (IU l−1), median (IQR)** | 38.95 (19.74)a | 29.40 (15.92)a,b | 21.95 (15.79)b | 13.09 (12.23)c | <0.001# |
| LH (IU l−1), median (IQR)** | 21.80 (11.52)a | 12.11 (7.29)b | 9.68 (4.53)b | 6.08 (3.97)c | <0.001# |
| Testosterone (µg l−1), median (IQR)** | 1.08 (2.47)b | 3.02 (3.04)a | 3.19 (2.83)a | 3.29 (1.79)a | 0.001# |
| Klinefelter syndrome, n (%)** | 19 (70.4)a | 2 (3.9)b | 1 (1.8)b | 0 (0)b | <0.001* |
| Y-chromosome microdeletion, n (%) | 2 (7.4) | 2 (3.9) | 3 (5.5) | 7 (15.9) | 0.175† |
| AZFb microdeletion, n (%) | 2 (7.4) | 1 (2.0) | 1 (1.8) | 4 (9.1) | 0.211† |
| AZFc microdeletion, n (%) | 0 (0) | 1 (2.0) | 1 (1.8) | 2 (4.5) | 0.753† |
| AZF(b+c) microdeletion, n (%) | 0 (0) | 0 (0) | 1 (1.8) | 1 (2.3) | 0.820† |
| History of mumps orchitis, n (%) | 0 (0) | 7 (13.7) | 5 (9.1) | 4 (9.1) | 0.233† |
| History of cryptorchidism, n (%) | 1 (3.7) | 3 (5.9) | 4 (7.3) | 0 (0) | 0.311† |
| Varicocele, n (%)** | 1 (3.7)a | 6 (11.8)a,b | 16 (29.1)b | 6 (13.6)a,b | 0.014* |
| History of cancer, n (%) | 1 (3.7) | 0 (0) | 4 (7.3) | 0 (0) | 0.071† |
| Hypothalamic pituitary dysfunction, n (%) | 0 (0) | 0 (0) | 1 (1.8) | 1 (2.3) | 0.820† |
| Gonadotoxins exposure, n (%) | 0 (0) | 0 (0) | 1 (1.8) | 0 (0) | >0.999† |
| Idiopathic NOA, n (%)** | 7 (25.9)a | 32 (62.7)a | 29 (52.7)a,b | 29 (65.9)b | 0.005* |
*Chi-square test; #Kruskal–Wallis one-way ANOVA; †Fisher’s exact test; 1Kruskal–Wallis one-way ANOVA showed significant differences in BMI among different testicular volume groups, but significance values adjusted by Bonferroni correction in the pairwise comparisons of the post hoc analysis showed no significant differences; 2The data in different TV groups labeled with different superscripted letters meant statistically significant (P<0.05), while data with the same superscripted letters meant statistically insignificant (P≥0.05). AZF: azoospermia factor; NOA: nonobstructive azoospermia; ANOVA: analysis of variance; TV: testicular volume; BMI: body mass index; FSH: follicle-stimulating hormone; LH: luteinizing hormone; IQR: interquartile range; NA: not applicable
Figure 1.
Flow chart of the study. NOA: non-obstructive azoospermia; micro-TESE: microdissection testicular sperm extraction; FSH: follicle-stimulating hormone; LH: luteinizing hormone; BMI: body mass index; AZF: azoospermia factor; TV: testicular volume.
The data were based on information from the clinical records and operative notes. All participants provided informed consent before their inclusion in the study. The present study was approved by the Ethical Committee of Shenzhen Zhongshan Obstetrics and Gynecology Hospital (formerly Shenzhen Zhongshan Urology Hospital; Approval No. SZZSECHU-F-2022057). Data that support the findings of this study are available from the corresponding author upon reasonable request.
Laboratory measurements
All patients preoperatively had semen analysis according to the 5th edition of World Health Organization guidelines.23 Azoospermia was diagnosed when the absence of sperm was observed after centrifugation (H1650; Cence, Changsha, China) at 3000g for 15 min and screened at 400× magnification (50i; Nikon, Tokyo, Japan) by at least two independent tests. Before micro-TESE surgery, NOA patients underwent comprehensive clinical evaluations to determine the etiology of azoospermia, including clinical history (undescended testis, mumps orchitis, previous genitourinary infection, surgical procedures, history of cancer, gonadotoxin exposure, alcohol consumption, and smoking), physical examination (secondary sexual characteristics, testicular size, height, weight, and the presence of a varicocele), and medical treatment (whether they accepted hormonal therapy within 3 months before surgery). TVs were measured using a Prader’s orchidometer.24 The average TV and surgical TV were recorded in our study. The average volume of the left and right testicles was referred to as the average TV. Surgical TV referred to the volume of the testicle incised for sperm retrieval when micro-TESE surgery was performed only on one side or the average volume of the left and right testicles when micro-TESE surgery was performed on both testicles. Reproductive hormone levels (FSH, LH, and testosterone) measurements were obtained within 3 months before the micro-TESE attempt. Karyotype and azoospermia factor (AZF) deletions of Y-chromosome analyses were also performed before surgery. Testicular biopsy was routinely performed during surgery in all patients undergoing micro-TESE, and fragments of the testicular parenchyma were sent to the pathology laboratory to further confirm spermatogenesis dysfunction.
Surgical procedure
Micro-TESE was performed under general anesthesia by a single experienced surgeon, as described in previous literature.10 An initial micro-TESE was performed on the larger testicle, and the contralateral testicle was explored for subsequent samples if no spermatozoa were identified in the previous sample. A middle incision in the equatorial region of the scrotum was widened transversally. The testicular parenchyma was examined systematically and carefully using an operating microscope (LZL-6A; Zhongtian Optics, Zhenjiang, China) with 18×–20× magnification, identifying opaque seminiferous tubules with increased diameters. The larger and more opaque seminiferous tubules were excised and then checked for spermatozoa under an inverted microscope (Ti2-U; Nikon) at 400× magnification. Positive sperm retrieval was defined as finding mature sperm. If sperm retrieval succeeded, the best testicular samples were collected for cryopreservation for further use. Testicular specimens were collected from each incision for pathological examination, regardless of the sperm retrieval results.
Testicular histopathology
A testicular specimen biopsied for histological evaluation was fixed in Bouin’s solution and sent to an external pathology laboratory (Guangzhou Huayin Medical Laboratory Center, Guangzhou, China). Based on the predominant histological pattern, the pathological findings were classified as normal spermatogenesis (NormoS), hypospermatogenesis (HypoS), maturation arrest (MA), Sertoli cell-only (SCO), tubular atrophy (TA), and mixed pattern (MP).
Statistical analyses
All the data were analyzed using IBM SPSS Statistics for Windows, version 26.0 (IBM Corp., Armonk, NY, USA). The normal distribution of variables was tested using the Shapiro–Wilk test. Due to the abnormal distribution of all continuous variables, the data are presented as the median and interquartile range (IQR) for continuous variables and nonparametric tests were used for difference comparisons. Differences between the two groups were assessed by the Mann–Whitney U test for the continuous variables. Differences among three or more groups and multiple comparisons were assessed by Kruskal–Wallis one-way analysis of variance (ANOVA) for the continuous variables. The categorical variables are described using frequency and percentage. Differences between groups were tested by the Chi-squared (χ2) or Fisher’s exact test. The associations between clinical and laboratory parameters and micro-TESE sperm retrieval outcomes were assessed by odds ratio (OR) and 95% confidence interval (CI) estimated by a binary logistic regression analysis. Multivariate and univariate logistic regression models were developed to analyze the relationship between TV, serum hormone levels, and micro-TESE outcomes. A two-sided P < 0.05 was considered statistically significant.
RESULTS
Testicular sperm was successfully retrieved in 57.6% (102/177) of the men with NOA who underwent micro-TESE in the present study. No significant differences were observed in age, BMI, the number of patients with smoking habits, TV (including average and surgical TV), the number of patients treated with hormonal therapy before micro-TESE surgery, preoperative serum hormonal profiles (including FSH, LH, and T), and all NOA etiological factors in positive and negative micro-TESE sperm retrieval outcomes (all P > 0.05). Table 1 summarizes the clinical and laboratory characteristics of the men with NOA enrolled in our study. The results of patients with AZFb deletions in the Y-chromosome were not concordant with those with complete AZFb deletions or complete AZF(b+c) deletions. All men with AZFb deletions had distal border (sY153 and/or sY1192) deletions, which may represent variable testicular phenotypes and the chance to obtain sperm in micro-TESE.25
Table 1.
Baseline characteristics of men with nonobstructive azoospermia undergoing microdissection testicular sperm extraction
| Characteristic | All patients | Positive sperm retrieval group | Negative sperm retrieval group | P |
|---|---|---|---|---|
| Number of patients, n (%) | 177 (100.0) | 102 (57.6) | 75 (42.4) | NA |
| Age (year), median (IQR) | 32 (7) | 31 (8) | 32 (5) | 0.943a |
| BMI (kg m−2), median (IQR) | 23.94 (4.33) | 23.54 (4.51) | 24.34 (4.40) | 0.278a |
| Smoking habit, n (%) | 28 (15.8) | 17 (16.7) | 11 (14.7) | 0.719b |
| Average TV (ml), median (IQR) | 5 (5) | 5 (2) | 5 (5) | 0.204a |
| Average of surgical TV (ml), median (IQR) | 5 (5) | 5 (3) | 5 (5) | 0.228a |
| Hormonal therapy, n (%)d | 23 (13.0) | 10 (9.8) | 13 (17.3) | 0.141b |
| Hormone profile | ||||
| FSH (IU l−1), median (IQR) | 23.07 (19.86) | 25.74 (21.50) | 21.32 (17.94) | 0.297a |
| LH (IU l−1), median (IQR) | 10.02 (9.71) | 10.10 (9.62) | 9.90 (8.19) | 0.735a |
| Testosterone (μg l−1), median (IQR) | 3.02 (2.59) | 2.97 (2.47) | 3.03 (2.89) | 0.915a |
| Klinefelter syndrome, n (%) | 22 (12.4) | 11 (10.8) | 11 (14.7) | 0.439b |
| Y-chromosome microdeletion, n (%)e | 14 (7.9) | 7 (6.9) | 7 (9.3) | 0.547c |
| AZFb microdeletion, n (%) | 8 (4.5) | 4 (3.9) | 4 (5.3) | 0.724c |
| AZFc microdeletion, n (%) | 4 (2.3) | 2 (2.0) | 2 (2.7) | >0.999c |
| AZF(b + c) microdeletion, n (%) | 2 (1.1) | 1 (1.0) | 1 (1.3) | >0.999c |
| History of mumps orchitis, n (%) | 16 (9.0) | 10 (9.8) | 6 (8.0) | 0.679b |
| History of cryptorchidism, n (%) | 8 (4.5) | 6 (5.9) | 2 (2.7) | 0.470c |
| Varicocele, n (%)f | 29 (16.4) | 19 (18.6) | 10 (13.3) | 0.347b |
| History of cancer, n (%) | 5 (2.8) | 2 (2.0) | 3 (4.0) | 0.652c |
| Hypothalamic pituitary dysfunction, n (%)g | 2 (1.1) | 2 (2.0) | 0 (0) | 0.509c |
| Gonadotoxins exposure, n (%) | 1 (0.6) | 0 (0) | 1 (1.3) | 0.424c |
| Idiopathic NOA, n (%) | 97 (54.8) | 56 (54.9) | 41 (54.7) | 0.975b |
aMann–Whitney U test. bChi-square test. cFisher’s exact test. dIn patients undergoing hormonal therapy prior to micro-TESE, 12 were intramuscularly injected with hCG combined with HMG, seven were intramuscularly injected with hCG combined with HMG and anti-estrogen per os, one was intramuscularly injected with purified or recombinant FSH, one was intramuscularly injected with HMG, one was intramuscularly injected with hCG combined with HMG and anti-estrogen per os after the down-regulation of gonadotropin-releasing hormone, and one was intramuscularly injected with hCG and bromocriptine per os. eIn the positive sperm retrieval subgroup, three patients had sY1192 deletions in AZFb, one had sY153 and sY1192 deletions in AZFb, one had sY239, sY242, sY254, sY152, and sY255 deletions in AZFc, one had sY254 and sY255 deletions in AZFc, one had sY153 and sY1192 deletions in AZFb, as well as sY254 and sY255 deletions in AZFc. In the negative sperm retrieval subgroup, four patients had sY1192 deletion in AZFb, two had sY254 and sY255 deletions in AZFc, and one had sY153 and sY1192 deletions in AZFb, as well as sY254 and sY255 deletions in AZFc. fThe positive sperm retrieval subgroup had two patients with postvaricocelectomy and 17 patients with untreated varicoceles, while 10 patients in the negative sperm retrieval subgroup had untreated varicoceles. gThe positive sperm retrieval subgroup included one patient with hypogonadotropic hypogonadism and one with panhypopituitarism. Micro-TESE: microdissection testicular sperm extraction; NA: not applicable; IQR: interquartile range; BMI: body mass index; FSH: follicle-stimulating hormone; LH: luteinizing hormone; AZF: azoospermia factor; HMG: human menopausal gonadotropin; hCG: human chorionic gonadotropin; NOA: nonobstructive azoospermia; TV: testicular volume
SCO was the major histopathological pattern (44.1%) in the overall included patients with NOA, indicating the severity of testicular histopathology in our study population. HypoS and SCO were the two major histopathological patterns observed in NOA patients who achieved positive sperm retrieval outcomes, with over one-third of patients being histopathologically diagnosed with each pattern (HypoS: 36.3%, SCO: 36.3%). However, SCO was predominantly found in NOA patients with negative sperm retrieval outcomes, accounting for over half of these cases (54.7%). Statistical analysis showed significant differences in the proportion of HypoS and SCO outcomes between patients with positive and negative sperm retrieval outcomes. The proportion of HypoS was significantly higher in the positive sperm retrieval group than in the negative sperm retrieval group (36.3% vs 21.3%, P = 0.032), whereas the proportion of SCO was statistically lower in the positive sperm retrieval group compared to the negative sperm retrieval group (36.3% vs 54.7%, P = 0.015). Table 2 lists the testicular histopathology of the men with NOA enrolled in our study.
Table 2.
Pathological diagnoses of men with nonobstructive azoospermia undergoing microdissection testicular sperm extraction
| Histopathology | All patients | Positive sperm retrieval group | Negative sperm retrieval group | P |
|---|---|---|---|---|
| NormoS, n (%) | 5 (2.8) | 5 (2.8) | 0 (0) | 0.074b |
| HypoS, n (%) | 53 (29.9) | 37 (36.3) | 16 (21.3) | 0.032a |
| MA, n (%) | 3 (1.7) | 2 (2.0) | 1 (1.3) | >0.999b |
| SCO, n (%) | 78 (44.1) | 37 (36.3) | 41 (54.7) | 0.015a |
| TA, n (%) | 35 (19.8) | 19 (18.6) | 16 (21.3) | 0.655a |
| MP, n (%) | 3 (1.7) | 2 (2.0) | 1 (1.3) | >0.999b |
aChi-square test. bFisher’s exact test. NormoS: normal spermatogenesis; HypoS: hypospermatogenesis; MA: maturation arrest; SCO: Sertoli cell-only; TA: tubular atrophy; MP: mixed pattern
We divided the subjects into four groups according to the four quantiles of TV, FSH, LH, and T levels and compared their SRRs to further investigate the sperm-obtaining outcomes in men with different TVs and preoperative serum hormone levels. Compared to the Q4 (TV ≥8 ml) average TV subgroup, the Q2 (3 ml ≤ TV < 5 ml) subgroup revealed a higher rate of positive sperm retrieval (68.6% vs 45.5%; OR: 2.63; 95% CI: 1.14–6.07, P = 0.024). However, no statistical differences were found in SRRs among serum FSH, LH, and T quartiles (all P > 0.05). The comparison of SRRs in each TV and serum FSH, LH, and T quantile in men with NOA is listed in Supplementary Table 1. Subsequently, the basic characteristics of the involved patients were compared in the four TV quantiles to investigate the potential impact of factors that might be related to TV (Supplementary Table 2). BMI, serum FSH, LH, and testosterone levels, as well as the numbers of Klinefelter syndrome, varicoceles, and idiopathic NOA, showed significant differences among the four TV quantiles (all P < 0.05), indicating that these factors might be influenced by TV.
As shown in Supplementary Table 1, TV might impact micro-TESE sperm retrieval outcomes, so the included patients were divided into four groups based on the four TV quantiles to compare the differences in hormone profiles between the positive and negative sperm retrieval subgroups (Table 3). Preoperative serum FSH and LH levels decreased with larger testicles in both the positive and negative sperm retrieval subgroups. However, serum testosterone levels did not increase when TV increased. The serum FSH levels (median [IQR]) in the positive sperm retrieval subgroups in the Q1 and Q2 average TV quantile groups were higher than those in the negative subgroup (Q1 [TV <3 ml]: 43.32 [17.92] IU l−1 vs 32.95 [18.56] IU l−1, P = 0.048; and Q2 [3 ml ≤ TV < 5 ml]: 31.31 [15.37] IU l−1 vs 25.59 [18.40] IU l−1, P = 0.042). In the Q3 (5 ml ≤ TV <8 ml) and Q4 (TV ≥8 ml) groups, no statistically significant differences were found in FSH levels between the positive and negative sperm retrieval subgroups (both P > 0.05), although the median FSH levels were lower in the positive sperm retrieval subgroup compared to the negative sperm retrieval subgroup. Additionally, no statistical differences were observed in serum LH and testosterone levels between the positive and negative sperm retrieval subgroups of any TV quartile (all P > 0.05).
Table 3.
Comparison of serum hormone levels in positive and negative sperm retrieval subgroups with different testicular volumes
| Parameter | Average of bilateral TV | |||
|---|---|---|---|---|
|
| ||||
| TV <3 ml | 3 ml ≤TV <5 ml | 5 ml ≤TV <8 ml | TV ≥8 ml | |
| Patient (n) | 27 | 51 | 55 | 44 |
| FSH (IU l−1), median (IQR) | ||||
| Positive sperm retrieval | 43.32 (17.92) | 31.31 (15.37) | 21.11 (15.36) | 8.67 (14.03) |
| Negative sperm retrieval | 32.95 (18.56) | 25.59 (18.40) | 24.68 (17.44) | 13.66 (8.79) |
| aP | 0.048 | 0.042 | 0.591 | 0.063 |
| LH (IU l−1), median (IQR) | ||||
| Positive sperm retrieval | 21.58 (9.90) | 12.19 (6.71) | 9.61 (5.09) | 5.53 (3.83) |
| Negative sperm retrieval | 21.87 (9.95) | 11.04 (7.59) | 9.68 (5.06) | 6.12 (4.63) |
| aP | 0.280 | 0.471 | 0.835 | 0.203 |
| Testosterone (µg l−1), median (IQR) | ||||
| Positive sperm retrieval | 1.73 (2.20) | 2.73 (2.39) | 3.45 (2.82) | 3.31 (2.71) |
| Negative sperm retrieval | 0.92 (3.28) | 4.04 (3.21) | 3.05 (2.26) | 3.18 (1.73) |
| aP | 0.550 | 0.350 | 0.522 | 0.934 |
aMann–Whitney U test. IQR: interquartile range; TV: testicular volume; FSH: follicle-stimulating hormone; LH: luteinizing hormone
TV and serum FSH levels did not influence micro-TESE sperm retrieval in the NOA males cohort as a whole, based on logistic regression analysis (Table 4). However, when the average TV was less than 5 ml, an increase in FSH by one unit increased the probability of positive sperm retrieval by 6% (adjusted OR: 1.06; 95% CI: 1.01–1.11; P = 0.011). When the average TV was equal to or larger than 5 ml, an increase in the average bilateral TV of 1 ml decreased the probability of positive sperm retrieval by 16% (adjusted OR: 0.84; 95% CI: 0.71–0.98; P = 0.029). Nevertheless, TVs had a limited effect on positive sperm retrieval in NOA patients with TVs lower than 5 ml, and serum FSH levels did not impact positive sperm retrieval in patients with TVs equal to or larger than 5 ml.
Table 4.
Univariate and adjusted multivariable analyses of testicular volume and serum follicle-stimulating hormone levels on microdissection testicular sperm extraction sperm retrieval outcomes in men with nonobstructive azoospermia
| Parameter | Univariate analysis | Multivariate analysis | ||
|---|---|---|---|---|
|
|
|
|||
| OR (95% CI) | P | Adjusted OR (95% CI) | P | |
| Overall | ||||
| Average bilateral TV (ml) | 0.93 (0.85–1.02) | 0.127 | 0.92 (0.83–1.03) | 0.140 |
| FSH (IU l−1) | 1.01 (0.99–1.03) | 0.267 | 1.01 (0.99–1.04) | 0.399 |
| TV <5 ml | ||||
| Average bilateral TV (ml) | 1.43 (0.953–2.15) | 0.084 | 1.62 (0.89–2.98) | 0.118 |
| FSH (IU l−1) | 1.05 (0.996–1.06) | 0.087 | 1.06 (1.01–1.11) | 0.011 |
| TV ≥5 ml | ||||
| Average bilateral TV (ml) | 0.88 (0.76–1.01) | 0.064 | 0.84 (0.71–0.98) | 0.029 |
| FSH (IU l−1) | 0.99 (0.96–1.02) | 0.496 | 0.97 (0.93–1.01) | 0.143 |
Adjusted OR represents estimates from the model adjusted for BMI and some etiological factors (including Klinefelter syndrome, varicoceles, and idiopathic NOA) according to the results of Supplementary Table 2. TV: testicular volume; FSH: follicle-stimulating hormone; CI: confidence interval; OR: odds ratio; BMI: body mass index; NOA: nonobstructive azoospermia
DISCUSSION
TV is correlated with testicular function, and serum hormone levels and total sperm counts are related to TV.26 Men with spermatogenic failure may have a history of or present with abnormal TV as typical characteristics.27 The number of spermatogonia is generally negatively correlated with FSH levels, and when spermatogonia are absent or significantly diminished, serum FSH levels are increased.28 These two preoperative parameters, although known as good indicators of global testicular function, might not predict the SRR of micro-TESE as effectively as they predict the SRR of cTESE or TESA. This is because rare foci of sperm production in testicles would be chosen during the micro-TESE procedure and the status of focal spermatogenesis would not be exactly reflected.13,29 Our results, which showed that average TV and preoperative serum FSH levels were not statistically different between the positive and negative sperm retrieval groups, also proved that these preoperative characteristics could not represent micro-TESE sperm retrieval outcomes in NOA patients.
The histopathological findings were helpful for predicting micro-TESE SRRs in NOA, and men with histopathological findings of HypoS would have higher SRRs.22,30 In NOA men with heterogeneous testicular histopathology, testicular tissue containing normal spermatogenesis and HypoS, as indicated by focal areas of spermatogenesis, also presented with higher micro-TESE SRRs.31 However, histopathological findings of no spermatozoa might not represent the hopelessness of obtaining sperm in the testicle of an NOA male undergoing micro-TESE. The individual seminiferous tubules, which most likely contained sperm, were cut into small pieces to allow spermatozoa to be released from the inside of the tubules and to further check for spermatozoa.10 The specimens for histopathological examinations were excised from other fragments of the testicular parenchyma. Therefore, the histopathological results of testicular tissue might not be consistent with the micro-TESE sperm retrieval outcomes (e.g., SCO men with 36.3% positive sperm retrieval in the present study). Although histopathology is probably the best single predictor of successful micro-TESE, its use is severely limited because it requires a separate surgical procedure for diagnosis.13 Thus, preoperative predictors hold wide appeal for andrologists due to their noninvasiveness and convenience.
Preoperative predictors of micro-TESE SRRs have been widely investigated in previous studies, and they attempted to provide important information for both NOA patients and surgeons performing micro-TESE.22,32 Serum FSH levels and TV are two frequently used preoperative indicators proven to be related to the success of TESE using the random biopsy technique.33 However, conflicting reports on the predictive values of serum FSH levels and TV for micro-TESE outcomes have been published, and their predictive value was limited.13,22 Some studies reported that the SRR of micro-TESE was not lower or even higher when serum FSH levels increased.19,34,35,36 In contrast, lower serum FSH levels were observed in NOA males with positive micro-TESE sperm retrieval.37,38,39 Meanwhile, no significant differences in serum FSH levels were reported between positive and negative sperm retrieval groups.30,40 Regarding the impact of TV on sperm retrieval, although NOA men with larger testicles would have higher chances of sperm retrieval in micro-TESE,39,41 decreased TV did not negatively affect the micro-TESE surgery SRR and these patients had even better sperm retrieval outcomes.20,34,36,38 Our results support that serum FSH levels and TV did not significantly influence SRRs and were poor predictive factors for the success of sperm retrieval in NOA patients undergoing micro-TESE in the cohort as a whole.
Decreased TV and elevated serum FSH levels do not indicate a low chance of positive sperm retrieval in micro-TESE, and increased serum FSH levels may be conductive to the success of micro-TESE in NOA men with small testicles. NOA is attributed to spermatogenic failure, which usually presents with abnormal TV and high levels of FSH and LH, with or without low testosterone levels.42 Small testicles accompanied by elevated serum FSH levels were reported to indicate a low probability of sperm retrieval by testicular sperm extraction in NOA men.14 Previous research by Ramasamy et al.19 reported that a preoperative FSH level higher than 15 IU l−1 resulted in greater odds of finding sperm with micro-TESE compared with normal FSH values in all of the included NOA patients. However, when the subjects in our study were categorized by TV, serum FSH levels were significantly correlated with micro-TESE sperm retrieval outcomes when the average TV was <5 ml, which might support the conclusions of previous research by Zhang et al.34 However, TV was negatively correlated with positive sperm retrieval, while serum FSH levels showed limited impact on the positive sperm retrieval outcomes of micro-TESE when the TV was equal to or more than 5 ml. These findings were not reported in previous literature, and additional data are needed to validate these results. Our results suggest that the association of FSH levels and TV with the success of sperm retrieval could be reconsidered depending on whether the TV is less than or greater than 5 ml.
CONCLUSION
In summary, conventional preoperative parameters, including TV and the serum hormone profile, have limited prognostic values for micro-TESE sperm retrieval outcomes. NOA patients with positive sperm retrieval via micro-TESE might present with elevated serum FSH levels when their TVs are less than 5 ml. NOA men with small testes may still benefit from micro-TESE even when FSH is elevated. When TVs are 5 ml or greater, larger testes do not necessarily equate better sperm retrieval success.
AUTHOR CONTRIBUTIONS
MZS and LJY substantially contributed to the design of this study and mainly drafted the manuscript. MZS and WQX performed the research and contributed to the data acquisition. LJY and WSH contributed to the statistical analysis of the data. WBW, SD and LYL contributed to the clinical data acquisition. YQP and QS carried out laboratory work. THW contributed to the data acquisition and analysis of Y-chromosome microdeletion. JC and YZ designed the research and critically revised the manuscript. All authors read and approved the final manuscript.
COMPETING INTERESTS
All authors declare no competing interests.
ACKNOWLEDGMENTS
This work was supported by the Shenzhen Fundamental Research Program (No. JCYJ20210324121807021).
Supplementary Information is linked to the online version of the paper on the Asian Journal of Andrology website.
REFERENCES
- 1.Vander Borght M, Wyns C. Fertility and infertility:definition and epidemiology. Clin Biochem. 2018;62:2–10. doi: 10.1016/j.clinbiochem.2018.03.012. [DOI] [PubMed] [Google Scholar]
- 2.Agarwal A, Baskaran S, Parekh N, Cho CL, Henkel R, et al. Male infertility. Lancet. 2021;397:319–33. doi: 10.1016/S0140-6736(20)32667-2. [DOI] [PubMed] [Google Scholar]
- 3.Cocuzza M, Alvarenga C, Pagani R. The epidemiology and etiology of azoospermia. Clinics (Sao Paulo) 2013;68(Suppl 1):15–26. doi: 10.6061/clinics/2013(Sup01)03. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Wu X, Lin D, Sun F, Cheng CY. Male infertility in humans:an update on non-obstructive azoospermia (NOA) and obstructive azoospermia (OA) Adv Exp Med Biol. 2021;1288:161–73. doi: 10.1007/978-3-030-77779-1_8. [DOI] [PubMed] [Google Scholar]
- 5.Practice Committee of the American Society for Reproductive Medicine. Management of nonobstructive azoospermia:a committee opinion. Fertil Steril. 2018;110:1239–45. doi: 10.1016/j.fertnstert.2018.09.012. [DOI] [PubMed] [Google Scholar]
- 6.Vasan SS. Azoospermia:diagnosis and management. In: Gunasekaran K, Pandiyan N, editors. Male Infertility:A Clinical Approach. New Delhi: Springer; 2017. pp. 85–106. [Google Scholar]
- 7.Brant A, Schlegel PN. Modern surgical treatment of azoospermia. Curr Opin Urol. 2023;33:39–44. doi: 10.1097/MOU.0000000000001055. [DOI] [PubMed] [Google Scholar]
- 8.Bernie AM, Mata DA, Ramasamy R, Schlegel PN. Comparison of microdissection testicular sperm extraction, conventional testicular sperm extraction, and testicular sperm aspiration for nonobstructive azoospermia:a systematic review and meta-analysis. Fertil Steril. 2015;104:1099–103. doi: 10.1016/j.fertnstert.2015.07.1136. e1–3. [DOI] [PubMed] [Google Scholar]
- 9.Wosnitzer M, Goldstein M, Hardy MP. Review of azoospermia. Spermatogenesis. 2014;4:e28218. doi: 10.4161/spmg.28218. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Schlegel PN. Testicular sperm extraction:microdissection improves sperm yield with minimal tissue excision. Hum Reprod. 1999;14:131–5. doi: 10.1093/humrep/14.1.131. [DOI] [PubMed] [Google Scholar]
- 11.Deruyver Y, Vanderschueren D, Van der Aa F. Outcome of microdissection TESE compared with conventional TESE in non-obstructive azoospermia:a systematic review. Andrology. 2014;2:20–4. doi: 10.1111/j.2047-2927.2013.00148.x. [DOI] [PubMed] [Google Scholar]
- 12.Craft I, Bennett V, Nicholson N. Fertilising ability of testicular spermatozoa. Lancet. 1993;342:864. doi: 10.1016/0140-6736(93)92722-6. [DOI] [PubMed] [Google Scholar]
- 13.Bernie AM, Ramasamy R, Schlegel PN. Predictive factors of successful microdissection testicular sperm extraction. Basic Clin Androl. 2013;23:5. doi: 10.1186/2051-4190-23-5. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Pantke P, Diemer T, Marconi M, Bergmann M, Steger K, et al. Testicular sperm retrieval in azoospermic men. Eur Urol Suppl. 2008;7:703–14. [Google Scholar]
- 15.Esteves S, Prudencio C, Seol B, Verza S, Knoedler C, et al. Comparison of sperm retrieval and reproductive outcome in azoospermic men with testicular failure and obstructive azoospermia treated for infertility. Asian J Androl. 2014;16:602–6. doi: 10.4103/1008-682X.126015. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16.Zitzmann M, Nordhoff V, von Schonfeld V, Nordsiek-Mengede A, Kliesch S, et al. Elevated follicle-stimulating hormone levels and the chances for azoospermic men to become fathers after retrieval of elongated spermatids from cryopreserved testicular tissue. Fertil Steril. 2006;86:339–47. doi: 10.1016/j.fertnstert.2005.12.058. [DOI] [PubMed] [Google Scholar]
- 17.Bromage SJ, Falconer DA, Lieberman BA, Sangar V, Payne SR. Sperm retrieval rates in subgroups of primary azoospermic males. Eur Urol. 2007;51:534–40. doi: 10.1016/j.eururo.2006.08.032. [DOI] [PubMed] [Google Scholar]
- 18.Colpi GM, Colpi EM, Piediferro G, Giacchetta D, Gazzano G, et al. Microsurgical TESE versus conventional TESE for ICSI in non-obstructive azoospermia:a randomized controlled study. Reprod Biomed Online. 2009;18:315–9. doi: 10.1016/s1472-6483(10)60087-9. [DOI] [PubMed] [Google Scholar]
- 19.Ramasamy R, Lin K, Gosden LV, Rosenwaks Z, Palermo GD, et al. High serum FSH levels in men with nonobstructive azoospermia does not affect success of microdissection testicular sperm extraction. Fertil Steril. 2009;92:590–3. doi: 10.1016/j.fertnstert.2008.07.1703. [DOI] [PubMed] [Google Scholar]
- 20.Bryson CF, Ramasamy R, Sheehan M, Palermo GD, Rosenwaks Z, et al. Severe testicular atrophy does not affect the success of microdissection testicular sperm extraction. J Urol. 2014;191:175–8. doi: 10.1016/j.juro.2013.07.065. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21.Kizilkan Y, Toksoz S, Turunc T, Ozkardes H. Parameters predicting sperm retrieval rates during microscopic testicular sperm extraction in nonobstructive azoospermia. Andrologia. 2019;51:e13441. doi: 10.1111/and.13441. [DOI] [PubMed] [Google Scholar]
- 22.Li H, Chen LP, Yang J, Li MC, Chen RB, et al. Predictive value of FSH, testicular volume, and histopathological findings for the sperm retrieval rate of microdissection tese in nonobstructive azoospermia:a meta-analysis. Asian J Androl. 2018;20:30–6. doi: 10.4103/aja.aja_5_17. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 23.World Health Organization. Laboratory Manual for the Examination and Processing of Human Semen. 5 th ed. Geneva: World Health Organization; 2010. p. p45. [Google Scholar]
- 24.Prader A. Testicular size:assessment and clinical importance. Triangle. 1966;7:240–3. [PubMed] [Google Scholar]
- 25.Krausz C, Navarro-Costa P, Wilke M, Tüttelmann F. EAA/EMQN best practice guidelines for molecular diagnosis of Y-chromosomal microdeletions:state of the art 2023. Andrology. 2024;12:487–504. doi: 10.1111/andr.13514. [DOI] [PubMed] [Google Scholar]
- 26.Sakamoto H, Ogawa Y, Yoshida H. Relationship between testicular volume and testicular function:comparison of the prader orchidometric and ultrasonographic measurements in patients with infertility. Asian J Androl. 2008;10:319–24. doi: 10.1111/j.1745-7262.2008.00340.x. [DOI] [PubMed] [Google Scholar]
- 27.Salonia A, Bettocchi C, Capogrosso P, Carvalho J, Corona G, et al. EAU Guidelines on Sexual and Reproductive Health. Arnhem:European Association of Urology. 2023. [[Last accessed on 2024 Feb 26]]. Available from: https://uroweb.org/guidelines/sexual-and-reproductive-health .
- 28.Matin-du-Pan RC, Bischof P. Increased follicle stimulating hormone in infetile men:is increased plasma FSH always due to damaged germinal epithelium? Hum Reprod. 1995;10:1940–5. doi: 10.1093/oxfordjournals.humrep.a136211. [DOI] [PubMed] [Google Scholar]
- 29.Tang D, Li K, He X, Zhang Y, Cao Y. Non-invasive molecular biomarkers for predicting outcomes of micro-TESE in patients with idiopathic non-obstructive azoospermia. Expert Rev Mol Med. 2022;24:e22. doi: 10.1017/erm.2022.17. [DOI] [PubMed] [Google Scholar]
- 30.Kavoussi PK, West BT, Chen SH, Hunn C, Gilkey MS, et al. A comprehensive assessment of predictors of fertility outcomes in men with non-obstructive azoospermia undergoing microdissection testicular sperm extraction. Reprod Biol Endocrinol. 2020;18:90. doi: 10.1186/s12958-020-00646-4. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 31.Punjani N, Flannigan R, Kang C, Khani F, Schlegel PN. Quantifying heterogeneity of testicular histopathology in men with nonobstructive azoospermia. J Urol. 2021;206:1268–75. doi: 10.1097/JU.0000000000001951. [DOI] [PubMed] [Google Scholar]
- 32.Arshad MA, Majzoub A, Esteves SC. Predictors of surgical sperm retrieval in non-obstructive azoospermia:summary of current literature. Int Urol Nephrol. 2020;52:2015–38. doi: 10.1007/s11255-020-02529-4. [DOI] [PubMed] [Google Scholar]
- 33.Chen XL, Wei YA, Ren XH, Zhang X, Li GY, et al. Predictive factors for successful sperm retrieval by microdissection testicular sperm extraction in men with nonobstructive azoospermia and a history of cryptorchidism. Asian J Androl. 2022;24:503–8. doi: 10.4103/aja2021102. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 34.Zhang H, Xi Q, Zhang X, Zhang H, Jiang Y, et al. Prediction of microdissection testicular sperm extraction outcome in men with idiopathic nonobstruction azoospermia. Medicine (Baltimore) 2020;99:e19934. doi: 10.1097/MD.0000000000019934. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 35.Amer MK, Ahmed AR, Abdel Hamid AA, GamalEl Din SF. Can spermatozoa be retrieved in non-obstructive azoospermic patients with high FSH level?A retrospective cohort study. Andrologia. 2019;51:e13176. doi: 10.1111/and.13176. [DOI] [PubMed] [Google Scholar]
- 36.Liu YP, Qi L, Zhang NN, Shi H, Su YC. Follicle-stimulating hormone may predict sperm retrieval rate and guide surgical approach in patients with non-obstructive azoospermia. Reprod Biol. 2020;20:573–9. doi: 10.1016/j.repbio.2020.10.006. [DOI] [PubMed] [Google Scholar]
- 37.Aljubran A, Safar O, Elatreisy A, Alwadai R, Shalkamy O, et al. Factors predicting successful sperm retrieval in men with nonobstructive azoospermia:a single center perspective. Health Sci Rep. 2022;5:e727. doi: 10.1002/hsr2.727. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 38.Deng CY, Liu DF, Zhao LM, Lin HC, Mao JM, et al. Development of a predictive model for increasing sperm retrieval success by microdissection testicular sperm extraction in patients with nonobstructive azoospermia. Asian J Androl. 2023;25:598–603. doi: 10.4103/aja2022111. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 39.Cetinkaya M, Onem K, Zorba OU, Ozkara H, Alici B. Evaluation of microdissection testicular sperm extraction results in patients with non-obstructive azoospermia:independent predictive factors and best cutoff values for sperm retrieval. Urol J. 2015;12:2436–43. [PubMed] [Google Scholar]
- 40.Enatsu N, Miyake H, Chiba K, Fujisawa M. Predictive factors of successful sperm retrieval on microdissection testicular sperm extraction in Japanese men. Reprod Med Biol. 2016;15:29–33. doi: 10.1007/s12522-015-0212-x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 41.Tsujimura A, Matsumiya K, Miyagawa Y, Takao T, Fujita K, et al. Prediction of successful outcome of microdissection testicular sperm extraction in men with idiopathic nonobstructive azoospermia. J Urol. 2004;172:1944–7. doi: 10.1097/01.ju.0000142885.20116.60. [DOI] [PubMed] [Google Scholar]
- 42.Alkandari MH, Zini A. Medical management of non-obstructive azoospermia:a systematic review. Arab J Urol. 2021;19:215–20. doi: 10.1080/2090598X.2021.1956233. [DOI] [PMC free article] [PubMed] [Google Scholar]