To determine the most useful index of pubertal gonadotropin secretion we measured spontaneous LH and FSH levels every 20 min for 24 h and the LH and FSH responses to LHRH in a total of 37 girls and 30 boys representing each of the 5 stages of puberty. Mean 24-h LH and FSH levels rose significantly with increasing pubertal stage in both girls and boys. LH peak amplitude increased significantly with increasing pubertal stage for both sexes, whereas FSH peak amplitude did not. LH and FSH peaks were present throughout the 24-h period in all children, but the frequency did not change significantly with increasing pubertal stage. Mean gonadotropin levels, peak amplitudes, and peak frequencies tended to be higher at night from pubertal stages 1-4 of puberty. There were no significant sex differences in mean LH, LH peak amplitude, or LH peak frequency. The LHRH-stimulated peak LH to peak FSH ratio was greater in boys than girls during pubertal stages 1-3 and was less useful in distinguishing pubertal from prepubertal boys. For girls, the most accurate index of pubertal gonadotropin secretion was a LHRH-stimulated peak LH to peak FSH ratio greater than 0.66, which detected 96% of the pubertal girls with no false positives. For boys, the most accurate index was a maximum spontaneous nighttime LH level of 12 IU/L or more, which detected 90% of the pubertal boys with no false positives. We conclude that there are important sex differences in the gonadotropin responses to LHRH during puberty, and that criteria for the onset of pubertal gonadotropin secretion should be sex specific.

To test the hypothesis that GH secretion increases during puberty, we measured GH levels in samples obtained every 20 min for 24 h from 132 normal children and adolescents. In both girls and boys, GH levels increased during puberty. The increase in mean levels was earlier in girls than boys, was most evident at night, and was due to increased pulse amplitude rather than a change in pulse frequency. The mean nighttime GH level in girls with bone ages (BA) greater than 12 to 14 yr were significantly greater than the mean level in girls with BA less than 8 yr (7.3 +/- 3.0 vs. 3.4 +/- 1.7 micrograms/L; P less than 0.01) and were greatest at breast stage 3 (7.9 +/- 2.5 micrograms/L). GH pulse amplitude increased significantly before pubertal onset in girls and was significantly greater at BA greater than 12 to 14 yr than at BA of 8 yr or less (13.9 +/- 6.0 vs. 7.9 +/- 4.8 micrograms/L; P less than 0.01) and greatest at breast stage 3 (15.0 +/- 6.3 micrograms/L). The pubertal increase in GH secretion was delayed in boys compared to girls, with the lowest mean 24-h GH and mean nighttime GH values in boys with BA greater than 8 to 11 yr. The mean nighttime GH level at BA greater than 11 to 13 yr in boys was significantly greater than that in the boys with BA greater than 8 to 11 yr (5.8 +/- 2.9 vs. 3.5 +/- 2.1 micrograms/L; P less than 0.05) and was greatest at a testicular volume of more than 10 to 15 mL (6.5 +/- 2.0 micrograms/L). The mean nighttime GH pulse amplitude in boys was significantly greater at BA greater than 11 to 13 yr than at BA greater than 8 to 11 yr (13.9 +/- 5.7vs. 7.3 + 2.6 micrograms/L, P less than 0.05) and was greatest at a testicular volume greater than 20 mL (15.8 +/- 12.0 micrograms/L). The mean nighttime GH levels correlated inversely with body mass index in both sexes, although the correlation achieved statistical significance only for the girls, being stronger in breast stage 3 to 5 girls (r = -0.57 P = 0.0007; n = 32) than in stage 1 and 2 girls (r = -0.38; P = 0.03; n = 32). These observations in normal adolescents emphasize the importance of interpreting spontaneous GH levels in short children in relation to normative data appropriate for sex, body mass, and bone age or pubertal stage.