PROGESTERONE OF THE BLOOD IN THE MENSTRUAL CYCLE OF THE MONKEY1

Abstract

The concn. of progesterone in the blood during normal and exptl. menstrual cycles in monkeys was detd. by the bio-assay method of Hooker and Forbes. There was general aggreement between results obtained from studies of normal cycles of 3 animals. Progesterone disappeared from the blood either immediately before or during menstruation and reappeared in detectable amts. within the 1st week of the cycle. This was followed by an increase in concn. toward the end of the follicular phase at approx. the time of expected ovulation. The concn. then declined until the 16th or 17th day, succeeded by a rapid increase until the max. concn. appeared near the mid-luteal phase. During the last half of this, the amt. in the blood decreased and was usually absent at the beginning of menstruation. The secretory life of the corpus luteum was not prolonged in 4 monkeys that were given prolactin during the luteal phase of the cycle. Menstruation occurred at the normal time and was preceded by the usual decrease of progesterone in the blood. The menstrual cycles of 2 monkeys given chorionic gonadotropin were prolonged 7 and 10 days beyond the expected normal duration. That this was due to a prolongation of luteal function was indicated by the continued presence of progesterone in the blood.