Comparison of the neuroendocrine control of pubertal maturation in girls and boys with spontaneous puberty and in hypogonadal girls.

Puberty in boys is characterized by a nocturnal increase in mean LH concentration and LH pulse frequency. To determine whether similar mechanisms exist in girls, nocturnal serum LH concentrations were determined in 16 girls with constitutional delay of adolescence or idiopathic short stature who had or have subsequently been shown to have spontaneous puberty. Mean LH and LH pulse frequency and amplitude were analyzed in 3-h blocks and compared to those in 20 pubertal boys. Girls had an increase in mean LH concentration from 3.6 +/- 0.7 IU/L at 2000-2250 h to 4.8 +/- 0.9 IU/L at 0200-0450 h. LH pulse frequency increased from 0.27 +/- 0.11 pulses/girl.h at 2000-2250 h to 0.54 +/- 0.10 pulses/girl.h at 0200-0450 h. The increase in LH pulse amplitude, from 2.0 +/- 0.8 IU/L at 2000-2250 h to 4.1 +/- 1.1 IU/L at 2300-0150 h, did not achieve statistical significance because many girls had no pulses from 2000-2250 h. With advancing age, the day/night differences in LH concentration and LH pulse frequency disappeared in girls, but were preserved in boys of same pubertal stage. The effect of lack of estrogen on LH pulse characteristics was inferred by analyzing the LH profiles of 15 girls with gonadal dysgenesis who were age-matched to girls with spontaneous puberty. The girls with gonadal dysgenesis had an increase in mean LH concentration after 0200 h, but LH pulse frequency was rapid in all time blocks; the nocturnal increase in LH concentration was secondary to a significant increase in LH pulse amplitude. Older girls with gonadal dysgenesis had a loss of nighttime augmentation of LH secretion similar to that seen in girls with spontaneous puberty. These data suggest that the apparent slower LH pulse frequency encountered in girls with spontaneous puberty during waking hours may be related to estrogen suppression of LH pulse amplitude, which masks the true daytime LH pulse frequency. With or without pubertal estrogen exposure, developmental progression of LH secretion occurs more rapidly in girls than in boys. Thus, intrinsic sex differences exist in the timing and tempo of endocrine control of pubertal maturation between boys and girls.