Diurnal Rhythms of Luteinizing Hormone, Follicle-Stimulating Hormone, Testosterone, and Estradiol Secretion before the Onset of Female Puberty in Short Children1

To investigate hormonal changes before the onset of female puberty, we measured LH and FSH in serum samples drawn every 20 min for 24 h and measured testosterone and estradiol hourly for 24 h. Seventeen girls (13 prepubertal and 4 early pubertal) of short stature, from 5.1-11.4 yr of age, participated in this study. LH and FSH were measured using a time-resolved immunofluorometric assay, and testosterone and estradiol were measured using a sensitivity RIA capable of detecting testosterone and estradiol concentrations of 10 and 2 pg/mL, respectively. Diurnal rhythms of LH, FSH, and testosterone were apparent in all subjects, including those aged 5-6 yr. Serum LH and FSH concentrations showed night-day variation in a pulsatile fashion. The serum testosterone concentration was elevated in the early morning in all subjects. The serum estradiol concentration was elevated in the early morning in 4 of 13 prepubertal subjects and all 4 early pubertal subjects. The diurnal pattern of the serum estradiol concentration was similar to that of the serum testosterone concentration. Mean 24-h LH and testosterone concentrations in prepubertal subjects who did not attain puberty for at least 1 yr were 0.07 U/L and 65 pg/mL, respectively, whereas those in prepubertal subjects who attained puberty within 1 yr (0.14 U/L and 106 pg/mL, respectively) were significantly higher. Furthermore, mean 24-h LH, FSH, testosterone, and estradiol concentrations increased with the onset of puberty. In conclusion, the diurnal rhythms of LH, FSH, and testosterone already exist at 5-6 yr of age, and serum LH and testosterone levels increase before the onset of puberty. These results suggest that preparation for the onset of female puberty may begin in 5- to 6-yr-old girls.