Luteinizing hormone and progesterone secretion during sexual maturation of the rhesus monkey: short luteal phases during the initial menstrual cycles

Abstract

Patterns of circulating progesterone were examined over a period of 1 1/2 years during the first 10 menstrual cycles of 10 untreated female rhesus monkeys of known age to determine precisely the onset of normal luteal function after menarche. Four of the 10 females did not exhibit elevated levels of serum progesterone (> 1 ng/ml) during any of the first 10 cycles, but the mean age and body weight at menarche in these females were not different from those in the 6 females in which increased levels of circulating progesterone were observed. In the latter 6 females, levels of circulating progesterone rose to > 1 ng/ml in 38 of 60 total cycles. Ten of these 38 cycles, however, had short luteal phases (9 ± 0.7 days vs. 16 ± 0.2 days for normal luteal phases), the luteal phase being defined as the interval from the midcycle LH peak to menses. The onset of cycles with short luteal phase occurred prior to the onset of cycles with normal luteal phases. During the first 5 cycles, when a preponderance of anovulatory (no LH surge, serum progesterone < 1 ng/ml) and short luteal phase cycles occurred, an extended interval between menses was observed (67 ± 10 days). Coincident with the onset of cycles with normal luteal phases in all 6 females (cycles 8-10) these periods decreased to lengths (30 ± 3 days) characteristic of the adult cycle. Because the short luteal phase has been implicated as an endocrine cause of infertility in women, the results of the present study suggest that the period of adolescent serility in the monkey during the first year after menarche may be derived not only from lack of ovulation, but from inadequate luteal function as well.