Masculinizing Hormone Therapy: What Happens to Estradiol and To Total, Free and Biovailable Testosterone?

Miguel Saraiva; Lia Ferreira; Isabel Palma

doi:10.1530/endoabs.90.P194

Introduction: Masculinizing Gender-Affirming Hormone Therapy (GAHT) generally aims to induce testosterone levels equivalent to those of cisgender men and to reduce estradiol levels. There are no studies about bioavailable testosterone in this population.

Aims: To determine the variation of the serum levels of sexual hormones in transmasculine people under GAHT and study the correlations between them and with BMI.

Methods: Longitudinal retrospective study which included adult transmasculine patients currently under follow up at our center. Data collected at 0, 6, 12, 24, 36 and 60 months of GAHT were analyzed.

Results: A total of 91 patients were included (85 trans men and 5 non-binary people). At the first visit at our center their median age was 24(20-28) years and their median BMI was 24.1(21.5-29.1) Kg/m². The median serum concentration of sexual hormones during follow-up was: Comparing with M0, at every visit there was a significant increase (P<0.001) in the serum level of testosterone – total, free and bioavailable. The reduction in the estradiol serum level only reached statistical significance at M60 (P=0.005). However, if the patients that underwent oophorectomy are excluded from the analysis, this reduction also becomes not significant at M60 (P=0.125). No correlation was found between the serum levels of estradiol or testosterones and BMI. Total testosterone serum levels showed a strong positive correlation with those of free and bioavailable testosterone (0.854 and 0.954, P<0.001). Only total testosterone serum levels reached statistical significance when testing the correlation with estradiol serum levels (-0.215, P=0.010).

Table 1
Months	M0	M6	M12	M24	M36	M60
N	78	15	6	13	11	12
Total testosterone (ng/ml)	0.34 (0.23-0.49)	4.26 (2.65-6.90)	4.78 (1.59-12.47)	4.53 (4.07-6.33)	4.93 (4.22-6.12)	4.20 (2.99-6.29)
Free testosterone (pg/ml)	1.66 (1.04-2.42)	12.22 (7.91-15.33)	10.55 (4.76-17.17)	10.71 (7.76-14.27)	9.84 (8.54-13.12)	7.95 (6.58-11.46)
Bioavailable testosterone (ng/ml)	0.10 (0.07-0.17)	2.84 (1.77-4.43)	2.51 (1.10-2.98)	2.80 (2.21-4.76)	2.76 (2.28-3.51)	2.65 (1.85-5.02)
Estradiol (pg/ml)	62.45 (34.08-132.00)	38.85 (29.08-60.08)	30.10 (25.48-43.08)	41.40 (29.00-65.80)	34.90 (24.90-74.00)	22.70 (18.50-55.25)

Conclusions: Masculinizing GAHT alone does not seem to be enough to significantly reduce estradiol serum levels, but oophorectomy seems to make a difference. Total testosterone correlates properly with free and bioavailable testosterone, which may imply that measuring the latter may be futile in most situations. Similarly to other studies, no correlations with BMI were found.

Endocrine Abstracts

P194