Androgen Inhibition of Reproductive Neuroendocrine Function in Females and Transgender Males.

Ovarian function is controlled by pituitary secretion of luteinizing hormone (LH) and follicle stimulating hormone (FSH), which in turn are governed by gonadotropin releasing hormone (GnRH) secreted from the brain. A fundamental principle of reproductive axis regulation is negative feedback signaling by gonadal sex steroids back to the brain to fine-tune GnRH and gonadotropin secretion. Endogenous negative feedback effects can be mimicked by exogenous steroid treatments, including androgens, in both sexes. Indeed, a growing number of clinical and animal studies indicate that high levels of exogenous androgens, in the typically male physiological range, can inhibit LH secretion in females, as occurs in males. However, the mechanisms by which male-level androgens inhibit GnRH and LH secretion still remain poorly understood, and this knowledge gap is particularly pronounced in transgender men (individuals designated female at birth but identifying as male). Indeed, many transgender men take long-term gender-affirming hormone therapy that mimics male-level testosterone levels. The impact of such gender-affirming testosterone on the reproductive axis, both at the ovarian and neuroendocrine level, is a long-understudied area that still requires further investigation. Importantly, the few concepts of androgen actions in females mostly come from studies of polycystic ovary syndrome, which does not recapitulate a similar androgen milieu or a pathophysiology of inhibited LH secretion as occurs in testosterone-treated transgender men. This review summarizes clinical evidence indicating that exogenous androgens can impair neuroendocrine reproductive function in both female individuals and transgender men and highlights emerging experimental data supporting this in recently developed transgender rodent models.