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 gonadotropin and testosterone concentrations around the onset of puberty and to determine the temporal relationship between the gonadotropin and testosterone secretion, plasma gonadotropin and testosterone were measured at 20-min intervals for 24 h in 21 normal short boys. The obtained plasma hormone concentrations were analyzed by Cluster pulse detection algorithm, cosinor analysis, and cross-correlation analysis. The 21 subjects 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 prepubertal group, all subjects showed nocturnal testosterone pulses and had significant circadian testosterone rhythms. The acrophase (clocktime of maximal value) of circadian testosterone rhythm was 0308-0428 h. Cross-correlation analysis demonstrated significant positive cross-correlations between LH and testosterone that were maximum at a testosterone lag of 60-120 min. Further, to eliminate intrinsic autocorrelations within the LH and testosterone time series, we filtered the data before subjecting them to the cross-correlation analysis. As a result, significant positive cross-correlations were found at a testosterone lag of 40 min in 10 peripubertal boys. We conclude that testosterone concentration profiles are pulsatile and show marked circadian rhythm well before the onset of puberty. LH and testosterone time series are significantly coupled when testosterone lags LH by about 40 min. This time lag might correspond to the time for synthesizing and secreting testosterone in Leydig cells after binding of LH to the Leydig cell receptors.