Circulating inhibin levels in lactating and nonlactating women

Abstract

To investigate the role of inhibin in the human puerperium, by measuring serum levels of immunoreactive inhibin in both lactating and nonlactating women. Prospective, comparative, open study. Department of obstetrics and gynecology of a university hospital. Fourteen healthy women who delivered at term: seven lactating women and seven nonlactating women treated with the dopamine-agonist CV 205-502. Serum immunoreactive inhibin, PRL, FSH, LH, E2, and P. All women showed a rapid decline of immunoreactive inhibin levels during the first postpartum days. Thereafter the pattern depended on the way of feeding. Nonlactating women, with their rapid return of pituitary and ovarian function, showed increasing immunoreactive inhibin levels to a maximum on day 24 (950 +/- 180 U/L). Lactating women did not show ovarian activity despite high FSH levels, and immunoreactive inhibin stayed on a low level (230 +/- 40 U/L on day 24). There was a significant correlation between immunoreactive inhibin and E2. The rapid decline of immunoreactive inhibin (elimination of placental hormone) is followed by an increase in nonlactating women (production by the maturing follicle) and by persistently low levels in lactating women. The lack of adequate levels of immunoreactive inhibin in lactating women may be an explanation of the relatively high FSH levels during lactation.