Ontogeny of luteinizing hormone secretion and first ovulation in seasonal breeding rhesus monkeys.

ABSTRACT

A longitudinal analysis assessed the role of nongonadal control and estradiol (E2) inhibition of LH secretion during puberty in female rhesus monkeys and examined how maturational changes in LH release were related to GH secretion, ponderal growth, and seasonal changes in the environment. Three groups of spring-born monkeys housed outdoors were studied from 12 months of age in May 1982 through 43 months of age in December 1984 gonadally intact (INT; n = 8), ovariectomized (OVX; n = 5), and OVX E2 treated (E2OVX; n = 5; E2, approximately 45 pg/ml). Suppression of bioactive levels of LH by E2 was functional once changes in nongonadal control of LH release occurred, as basal LH levels increased significantly earlier in OVX (23.7 +/- 2.1 months) than either E2OVX (29.6 +/- 0.4 months) or INT (29.6 +/- 1.0 months). Although these increases in LH were not seasonally limited, higher levels were achieved if these initial increases occurred during the fall. Menarche in INT females occurred after the initial increases in LH (30.9 +/- 0.1 months). First ovulation for INT females was seasonally restricted, occurring either at 31.5 +/- 0.4 months in December/January (n = 3) or 11 months later at 42.5 +/- 0.4 months in October/November (n = 5). No ovulations occurred during the intervening spring and summer period, as serum levels of LH were significantly lower than in the preceding perimenarchial fall months. After the initial maturational increases, LH levels declined significantly in OVX and E2OVX females in late winter at 33 months before rising again the next fall. The timing and extent of the maturational decrease in E2 inhibition of LH secretion were related to developmental increases in serum GH and not to body weight. Furthermore, females who had a normal first ovulation shortly after menarche at 31 months had significantly higher serum GH levels yet similar growth rates and body weights compared to their age-mates. First ovulation at 43 months in the remaining females occurred after sustained elevations in serum GH, similar to those observed in the early ovulating females. These data indicate that both nongonadal control and steroid inhibition of LH secretion operate during puberty in female rhesus monkeys and support the hypothesis that the final stages of puberty are characterized by a maturational decrease in E2 negative feedback of LH secretion.(ABSTRACT TRUNCATED AT 400 WORDS)