Serum prolactin, gonadotropins, and estradiol in menstruating and amenorrheic mothers during two years' lactation.

Serum prolactin, LH, FSH, and estradiol were measured in single blood samples collected from 465 nursing mothers in Central Africa (Kivu, Zaïre) during the first 2 postpartum years. Lactating mothers were hyperprolactinemic during 15 to 18 postpartum months. Both serum prolactin and FSH were higher in amenorrheic than in menstruating nursing mothers; the difference was more apparent during the first than during the second year. Mean serum LH and estradiol were significantly higher in menstruating then in amenorrheic nursing mothers during the second postpartum year but not during the first. There was a significant association of hyperprolactinemia with amenorrhea. Furthermore, postpartum, the incidence of amenorrhea declined parallel to that of hyperprolactinemia.