The ovarian function of transgender men was preserved after one year of testosterone therapy, a small study has found.
Some trans men choose testosterone therapy as part of their gender-affirming treatment. However, the long-term effects of this therapy on fertility are not fully understood. The study, presented at the ENDO (Endocrine Society) 2019 conference in New Orleans, Louisiana, found indications that fertility in trans men taking testosterone remained for longer than previously thought.
'Because the long-term effects of testosterone therapy on fertility are unknown, the current recommendation is to stop testosterone at least three months before fertility treatments,' said Professor Yona Greenman, of Tel Aviv University School of Medicine, Israel, who led the study.
The researchers set out to investigate the effect of testosterone therapy on trans men over a period of 12 months. They recruited 52 trans men, aged between 17 and 40, to the study.
The researchers measured the levels of three different hormones - testosterone, oestradiol and anti-Müllerian hormone. They reported the expected increase in testosterone levels due to the treatment. They also measured a decrease in levels of oestradiol, an oestrogen hormone that regulates the menstrual cycle.
There was a slight decrease in the levels of anti-Müllerian hormone, from 5.65 nanograms per millilitre (ng/ml) before treatment to 4.89 ng/ml after the treatment. Anti-Müllerian hormone is produced by the ovaries and the level of this hormone is used to estimate the number of eggs remaining in the ovaries, known as the ovarian reserve.
'This level [after treatment] likely indicates well-preserved ovarian function,' said Professor Greenman.
The researchers also measured other ovarian factors indicating fertility by performing pelvic ultrasounds from a subset of 32 of the study participants. They measured the antral follicular count - another indicator of the ovarian reserve - and thickness of the endometrium, which is important for embryo implantation. These remained unchanged after treatment.
Professor Greenman said: 'There is a need to investigate the effects of testosterone on further fertility parameters such as quality of oocytes and in vitro fertilised embryos.
'These results are a further step toward providing transgender people basic rights such as reproduction.'