Male Sexual Development in the Monkey. II. Cross-Sectional Analysis of Pulsatile Hypothalamic-Pituitary Secretion in Castrated Males*

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Abstract
Pulsatile secretion of serum gonadotropins was studied in 16 castrated monkeys from 4 weeks of age through adult life. Animals were castrated at various ages from birth through adult life. Although some studies of the gonadotropinsecretory patterns were longitudinal in nature, most comparisons were cross-sectional. On the basis of our observations, we have arbitrarily grouped the animals into 4 developmental ages: postnatal (in vitro bioassay for LH. During the frequent sampling period (24 h for all except postnatal animals), the amplitude of gonadotropin pulses was greatest in adult animals followed by postnatal and pubertal monkeys. During pubertal development, there was a marked increase in the magnitude of gonadotropin pulses, and remarkedly, there was a substantial increase in the LH bioassay: RIA (>5:1) by adult life. GnRH challenge tests of gonadotropins correlated with these observations. Time series analysis was applied to the data for objective statistical characterization of cyclic patterns. Our findings can be summarized: 1) during pubertal maturation there is a change in amplitude but not frequency of gonadotropin pulses, 2) pubertal development of the hypothalamic-pituitary axis advances in the absence of gonadal feedback, and 3) there is a significant increase in the LH bioassay: RIA during pubertal development. We conclude that the castrate monkey is a valuable adjunct to direct clinical investigations of the mechanisms controlling human sexual development. (J Clin Endocrinol Metab56: 1227, 1983)

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