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Nocturnal Secretory Dynamics of Inhibin B and Testosterone in Pre- and Peripubertal Boys

Department of Pediatric Biochemistry (P.M.C.), Royal Hospital for Sick Children, Edinburgh EH9 1LF, United Kingdom; Section of Child Life and Health (P.M.C., A.E.M.E., C.J.H.K.), Department of Reproductive and Developmental Sciences, University of Edinburgh EH9 1UW, Edinburgh, United Kingdom; Department of Biochemistry (A.M.W.), Royal Infirmary, Glasgow G4 OSF, United Kingdom; and School of Biological and Molecular Sciences (N.P.G.)., Oxford Brookes University, Oxford OX3 0BP, United Kingdom

Address all correspondence and requests for reprints to: Dr. P. M. Crofton, Department of Pediatric Biochemistry, Royal Hospital for Sick Children, Sciennes Road, Edinburgh EH9 1LF, United Kingdom. E-mail: patricia.crofton{at}luht.scot.nhs.uk.

To investigate the secretory dynamics of testosterone and inhibin B, we collected samples every 20 min from 2000 h to 0800 h in 20 boys. Boys in group 1 (n = 5) were aged less than 8 yr, group 2 (n = 5) were aged more than 8 yr but 1.5 yr or more before pubertal onset, group 3 (n = 5) were studied 1.0 yr or less before pubertal onset, and group 4 (n = 5) were in early puberty. Testosterone increased after midnight in peripubertal boys, coinciding with the onset of LH pulsatility, and showed a pulsatile pattern in 6 of 10 of these boys. Cross-correlation analysis indicated significant temporal coupling between LH and testosterone. Inhibin B was higher in groups 3 and 4, compared with groups 1 and 2 (P < 0.01) and showed a downward trend overnight with no evidence of pulsatility and no evidence of short-term interactions with LH, FSH, or testosterone. Inhibin B and LH nocturnal means were both inversely correlated with time before pubertal onset (r_s -0.85, P < 0.01). Only LH nocturnal mean and amplitude, respectively, contributed independently to prediction of testosterone and inhibin B nocturnal means, explaining 71 and 65% of their variability. We conclude that both testosterone and inhibin B are related to nocturnal LH release in peripubertal boys but over different time scales.

This study was supported by the Medical Research Council of the United Kingdom and the HEBA Trust.

Abbreviations: G2, Genital stage 2; r_k, correlation of two data arrays at a lag time of k units apart.

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