Abstract
Abstract
The hypothalamic–pituitary–gonadal (HPG) axis coordinates reproductive function and incorporates gonadal sex steroid feedback to regulate gonadotropin secretion in a homeostatic manner. In females, ovarian estrogens and progestins act as the primary negative feedback signals to suppress luteinizing hormone (LH) release, whereas in males, androgens, such as testosterone (T), typically provide this feedback. However, androgens can also exert feedback effects on the female HPG axis, particularly in conditions where circulating T levels exceed that of the normal female physiological range. Three clinically relevant examples are anabolic substance abuse, testosterone therapy, and polycystic ovary syndrome (PCOS; recently renamed polyendocrine metabolic ovarian syndrome [PMOS]). Despite shared exposure to “androgen excess,” these different hyperandrogenic states are associated with strikingly different neuroendocrine phenotypes. In testosterone therapy and anabolic substance abuse, high exogenous androgen exposure in or above the male physiological range typically suppresses LH secretion and disrupts ovulatory cycling, mimicking enhanced negative feedback on the HPG axis. Conversely, in PMOS, endogenous elevations in T, high for a female but below the male physiological range, are associated with increased LH secretion, acyclicity, and anovulation. The mechanisms underlying these divergent LH outcomes remain unclear but may reflect, in part, differences in the source of androgens (exogenous vs. endogenous), circulating androgen concentrations, and development timing and/or duration of androgen exposure. This review synthesizes current clinical and preclinical evidence to compare distinct models of hyperandrogenemia with respect to the female HPG axis and aims to illuminate how endogenous and exogenous androgens with different features differentially alter female neuroendocrine function.