Although hyperprolactinemia may be associated with hyperandrogenism, if hirsutism develops, it is usually a mild form. This study was designed to investigate whether prolactin (PRL) modulates 5α-reductase activity (5α-RA), because 5α-RA is known to be a major factor influencing the manifestation of androgenicity. Compared with normal women, euprolactinemic hirsute and both hyperprolactinemic hirsute and nonhirsute women had elevated levels of unbound testosterone (uT). Serum 3α-androstanediol glucuronide (3α-diol-G) was elevated only in patients who were hirsute, and serum 3α-diol-G/uT ratios were elevated in euprolactinemic hirsute patients and normal in hyperprolactinemic hirsute patients. Genital skin 5α-RA in vitro was elevated only in euprolactinemic hirsute women. The previously recognized positive correlation between 5α-RA and the severity of hirsutism was dissociated with hyperprolactinemia. Human PRL incubated in vitro with normal genital skin also inhibited 5α-RA. These data suggest that PRL modulates 5α-RA and peripheral androgen metabolism and that other factors may also be involved in the evolution of hirsutism in hyperprolactinemia.
Serafini, P., & Lobo, R. A. (1986). Prolactin modulates peripheral androgen metabolism. Fertility and Sterility, 45(1), 41–46. https://doi.org/10.1016/S0015-0282(16)49094-1