Pretreatment homocysteine and molecular endothelial risk in transgender women starting estrogen-based hormone therapy

Cardiovascular risk prediction tools such as SCORE2 and the Framingham Risk Score were developed for middle-aged and older adults (typically ≥40 years) and often substantially underestimate vascular susceptibility in younger individuals, since they are not validated in this age range (van Os et al., 2023). This limitation becomes critical in settings where non-age-dependent prothrombotic mechanisms are involved, such as the initiation of estrogen-based gender-affirming hormone therapy (GAHT) in transgender women. Current clinical guidance does not recommend routine thrombophilia screening before GAHT unless there is a personal or familial history of venous thromboembolism (Coleman et al., 2022), consistent with recommendations for estrogen-containing therapies in the general population (Curtis et al., 2016; Practice Committee of the American Society for Reproductive Medicine, 2017) and with expert consensus discouraging indiscriminate thrombophilia testing (Connors, 2017; Cuker et al., 2023).

We prospectively assessed 16 consecutive young transgender women (median age 27 years, IQR 22–31), naïve to estrogen therapy, at the Andrology Unit of San Salvatore Hospital, L’Aquila. Baseline evaluation included anthropometry, blood pressure, lipid profile, and calculation of SCORE2 and Framingham scores, which were used only for descriptive classification. To explore vascular susceptibility, we performed a classical thrombophilia panel (antithrombin III, protein C and S, factor V Leidenprothrombin G20210A mutation, antiphospholipid antibodies), which was extended to additional coagulation- and endothelial-related factors. Among these, fasting plasma homocysteine was measured by high-performance liquid chromatography. The study was conducted in accordance with the Declaration of Helsinki and was approved by the local Ethics Committee of the University of L’Aquila. Written informed consent was obtained from all participants prior to enrollment. Hyperhomocysteinemia, defined as >12 µmol/L (mild 13–30 µmol/L, intermediate 31–100 µmol/L), unexpectedly emerged as the predominant abnormality: 10 of 16 participants (62.5%) showed elevated levels, including four of six individuals without any conventional cardiovascular risk factors. Eight had mild elevation, while two had intermediate values (>30 µmol/L) and were homozygous for the MTHFR C677T variant. No severe hyperhomocysteinemia (>100 µmol/L) or other inherited/acquired thrombophilic conditions were detected.

These findings suggest that in young transgender women, considered at low risk by standard algorithms and not candidates for thrombophilia testing under current guidelines, homocysteine measurement may unmask a latent prothrombotic susceptibility. The biological plausibility of this observation is reinforced by extensive experimental evidence: Lentz (2005) first described how hyperhomocysteinemia promotes endothelial dysfunction through oxidative stress and impaired nitric oxide signaling, more recent data by Yuan et al. (2023) highlighted its pro-inflammatory and prothrombotic effects on the vascular endothelium, and finally Jakubowski and Witucki (2025) further expanded on novel molecular pathways linking elevated homocysteine to cardiovascular disease.

While large intervention trials failed to show benefit from homocysteine lowering (Bønaa et al., 2006), recent evidence supports its role as a biomarker of vascular risk: elevated levels predict events particularly in men (Zhang et al., 2020), remain associated with all-cause and cardiovascular mortality in cohort analyses; however, Mendelian randomization analyses do not appear to support a causal association with mortality (Choi et al., 2023). Consistent with a mechanistic link, elevated homocysteine has been tied to subclinical myocardial injury and cardiovascular death (Tan et al., 2024).

Our study has limitations. The small sample size, single-center design, and absence of a cisgender control group or longitudinal follow-up limit generalizability and preclude inference on incident venous or arterial events. As homocysteine testing was performed within an extended thrombophilia panel, the association observed should be interpreted as exploratory. Nonetheless, the internal consistency and the unexpected predominance of hyperhomocysteinemia in this young, otherwise low-risk cohort highlight the potential value of targeted testing in this setting.

In conclusion, homocysteine measurement unexpectedly emerged as the most frequent abnormality in young transgender women considered low-risk by conventional algorithms and not candidates for thrombophilia testing under current guidance. As a simple, inexpensive and widely available assay, homocysteine testing may complement current approaches by unmasking latent vascular susceptibility in contexts where standard risk scores underestimate thrombotic risk. Larger, prospective studies are needed to determine whether pretreatment hyperhomocysteinemia predicts vascular events during GAHT and whether its correction improves safety.

Daniele Tienforti, Giovanni Terrana, Adriano Ciriani, Luca Spagnolo, Marco Giorgio Baroni and Arcangelo Barbonetti
Andrology Unit, Department of Clinical Medicine, Life, Health and Environmental Sciences, University of L’Aquila, L’Aquila, Italy
danieletienforti@gmail.com

Correction Statement

This article was originally published with errors, which have now been corrected in the online version. Please see Correction (http://dx.doi.org/10.1080/26895269.2025.2564591).

Funding Statement

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Table 1.

Homocysteine levels and conventional cardiovascular risk factors in 16 AMAB individuals prior to gender affirming hormone therapy.

Patient	Framingham risk factors	SCORE2 risk factors	Homocysteine (µmol/L)	Hyperhomocisteinemia
1	0	0	11.6	–
2	0	0	92.8	Intermediate
3	2	3	10.2	–
4	1	1	18.8	Moderate
5	0	0	20.2	Moderate
6	1	0	60	Intermediate
7	0	0	11.5	–
8	2	2	24	Moderate
9	2	2	19.1	Moderate
10	0	0	18.8	Moderate
11	0	0	12.7	Moderate
12	2	1	10.6	–
13	1	2	27	Moderate
14	1	1	11.5	–
15	1	1	9.2	−
16	1	2	14	Moderate