SPONTANEOUS GONADOTROPIN AND TESTOSTERONE CONCENTRATION PROFILES IN PREPUBERTAL AND PUBERTAL BOYS - TEMPORAL RELATIONSHIP BETWEEN LUTEINIZING-HORMONE AND TESTOSTERONE

To investigate the detailed pattern of change in circulating gonadotro pin and testosterone concentrations around the onset of puberty and to determine the temporal relationship between the gonadotropin and test osterone secretion, plasma gonadotropin and testosterone were measured at 20-min intervals for 24 h in 21 normal short boys. The obtained pl asma hormone concentrations were analyzed by Cluster pulse detection a lgorithm, cosinor analysis, and cross-correlation analysis. The 21 sub jects were divided into the prepubertal (n = 16) and early pubertal (n = 5) groups. All subjects showed nocturnal LH and FSH pulses and had significant circadian LH and FSH rhythms. Except for six boys of prepu bertal group, all subjects showed nocturnal testosterone pulses and ha d significant circadian testosterone rhythms. The acrophase (clocktime of maximal value) of circadian testosterone rhythm was 0308-0428 h. C ross-correlation analysis demonstrated significant positive cross-corr elations between LH and testosterone that were maximum at a testostero ne lag of 60-120 min. Further, to eliminate intrinsic autocorrelations within the LH and testosterone time series, we filtered the data befo re subjecting them to the cross-correlation analysis. As a result, sig nificant positive cross-correlations were found at a testosterone lag of 40 min in 10 peripubertal boys. We conclude that testosterone conce ntration profiles are pulsatile and show marked circadian rhythm well before the onset of puberty. LH and testosterone time series are signi ficantly coupled when testosterone lags LH by about 40 min. This time lag might correspond to the time for synthesizing and secreting testos terone in Leydig cells after binding of LH to the Leydig cell receptor s.