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

Neonatal and Pediatric Medicine Branch and Biometry Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20205

Address requests for reprints to: Barry B. Bercu, M.D., Building 10, Room 8C429, Neonatal and Pediatric Branch National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20205.

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 (<7 months), prepubertal or juvenile (7–27 months), pubertal (28–59 months), and adult (60 months). In carrying out these studies, blood was withdrawn at 15-min intervals over 24 h without anesthesia using a mobile vest and tether assembly to support an indwelling catheter. GnRH challenge tests were done on 1 or more occasions on all animals. Plasma samples were analyzed for concentrations of FSH and LH by established RIAs and an 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 Metab 56: 1227, 1983)

^* Parts of this manuscript were presented at the Society for the Study of Reproduction, Corvallis, Oregon, 1981; Lawson Wilkins Pediatric Endocrine Society and the European Pediatric Endocrine Society, Geneva, Switzerland, 1981; Second International Conference on the Control of the Onset of Puberty II, Stresa, Italy, 1981; Society for Pediatric Research, Washington, DC, 1982; and the 64th Annual Meeting of The Endocrine Society, San Francisco, CA, 1982.

Received June 28, 1982.

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