Prolactin Activity in Blood During the Normal Human Menstrual Cycle.

Abstract

Summary Prolactin activity appeared in the blood of normal young women during the first 5 and last 10 days of a 28-day menstrual cycle, whereas no activity was demonstrable during days 6 to 18 of the cycle. Blood prolactin activity appeared to be present in the latter part of the cycle of a normal woman receiving the gonadotropin inhibitor, Enovid. No blood prolactin activity was found in a normal male subject during a 31-day period. These observations suggest that prolactin acts in opposition to the other 2 pituitary gonadotropins, FSH and LH, in the normal human menstrual cycle.