Analysis of secretory patterns of prolactin and gonadotropins during twenty-four hours in a lactating woman before and after resumption of menses

Twenty-four hour secretory patterns of prolactin, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were obtained on two separate occasions from a woman with late physiologic lactation. The studies were performed 26 and 34 months after her child's birth. During the initial study, she had amenorrhea, and her child suckled 13 per cent of the 24 hour period (Study 1). At the time of the second study, she had resumed regular menses and her child suckled for 7 per cent of the 24 hour period (Study 2). The average concentrations of prolactin during Studies 1 and 2 were 40 ± 1.0 (mean and standard error; No. = 72) and 31 ± 1.4 ng. per milliliter, respectively. The mean plasma prolactin concentration in Study 1 was significantly greater than that in Study 2 (p < 0.001). The plasma concentrations of LH and FSH were significantly less in Study 1 than in Study 2 (p < 0.001 and <0.01, respectively). It is concluded that hyperprolactinemia and hypogonadotropinemia were endocrinologic correlates of the amenorrhea of late physiologic lactation in this woman.