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Context: Puberty is marked by sleep-associated changes in LH pulse frequency and amplitude. Early pubertal girls with obesity exhibit blunted day-to-night changes in LH secretion; whether this occurs in late pubertal obese girls is unknown., Objective: The objective of the study was to test two hypotheses: 1) blunted day-to-night changes in LH secretion occur in both early and late pubertal obese girls, and 2) such alterations are specifically associated with hyperandrogenemia., Design: This was a cross-sectional analysis., Setting: The study was conducted at a clinical research center., Patients or Other Participants: Twenty-seven early pubertal, premenarcheal girls (12 of whom were obese) and 63 late pubertal (postmenarcheal) girls (27 of whom were obese) participated in the study., Intervention: Blood samples were taken every 10 minutes from 7:00 pm to 7:00 am., Main Outcome Measure: Change in LH pulse frequency [LH interpulse interval (IPI)] from daytime hours (7:00 pm-11:00 pm, while awake) to nighttime hours (11:00 pm to 7:00 am, while generally asleep)., Results: Both nonobese and obese postmenarcheal girls demonstrated significant day-to-night decreases in LH pulse frequency (IPI increases of 33% and 16%, respectively), but day-to-night changes were blunted in obese girls (P = .004, obese vs nonobese). Day-to-night LH pulse frequency decreased significantly in postmenarcheal obese subjects with normal T concentrations (26% IPI increase) but not in those with hyperandrogenemia. Similar differences were evident for LH pulse amplitude. Nonobese and obese early pubertal girls exhibited nonsignificant differences in day-night LH pulse frequency (day to night IPI increase of 26% vs decrease of 1%, respectively)., Conclusions: Day-to-night changes in LH pulse secretion are blunted in postmenarcheal obese adolescent girls. This phenomenon may in part reflect hyperandrogenemia.

The regulation of androgen synthesis during puberty in females is complicated, with changes in steroidogenic and peripheral interconversion capacity. In the present study we have investigated the diurnal rhythm of testosterone secretion in 56 healthy girls before and during puberty, up to 2 yr postmenarche. The girls' ages ranged between 4.6-16.5 yr, and their height SD scores ranged between -3.6 and +3.7. One to 5 serum profiles (seven samples per 24 h) were taken from each girl for steroid measurements, and a total of 84 serum profiles were obtained. Serum testosterone concentrations were determined using a RIA with a detection limit of 30 pmol/L. The results demonstrate that there is a diurnal rhythm of testosterone secretion during both prepuberty and puberty in girls. The pattern has its nadir in the late evening or just after midnight, with the highest levels in the morning (0600-1000 h). Serum testosterone concentrations in prepubertal girls were significantly lower than those in pubertal girls and were significantly lower in early puberty than in girls in mid- or late puberty. No differences were found in levels between girls in midpuberty or late puberty. Before puberty, serum testosterone concentrations correlated with serum dehydroepiandrosterone sulfate, consistent with the adrenals being the major source of testosterone. After the onset of puberty, a correlation between testosterone and 17beta-estradiol was seen, consistent with the ovaries being the major source of testosterone during puberty. Furthermore, the present study showed that there is a relative hyperandrogenicity in early puberty, with high levels of androgens relative to estrogens.

Puberty is initiated by a nocturnal rise in gonadotropin secretion, which, in boys, results in an increased nocturnal secretion of testosterone. To characterize any similar diurnal rhythm of 17 beta-estradiol in healthy girls, we determined the secretion of 17 beta-estradiol before and during puberty. The study group consisted of 45 healthy girls whose height SD scores ranged from -3.7 to +4.9 compared with Swedish growth reference values. One to 6 profiles of 17 beta-estradiol (7 samples/24 h) were obtained from each girl during puberty and from 21 of the girls before clinical signs of puberty (a total of 76 serum profiles). Serum 17 beta-estradiol concentrations were determined using a modified RIA. The detection limit for the RIA was 1.8 fmol/tube, which corresponded to a serum level of 7.8 pmol/L in extracted serum. It was considered that levels above 50 pmol/L could be determined accurately without extraction. The serum levels of 17 beta-estradiol in prepubertal girls were, in most cases, below the detection limit, except in the morning, when in 17 of the 21 prepubertal girls, serum 17 beta-estradiol levels were just above the detection limit. All girls in early puberty (Tanner breast stage 2) had measurable serum levels of 17 beta-estradiol in the morning, whereas 10 of these 15 girls had levels below the detection limit around midnight. Later in puberty (Tanner breast stages 3 and 4), but before menarche, the diurnal rhythm was more obvious, with high levels of 17 beta-estradiol during the latter part of the night and in the morning. This diurnal rhythm was lost by 1 yr after menarche. There was a high degree of correlation between serum concentrations of 17 beta-estradiol and bone age, whereas there was much less, if any, correlation between 17 beta-estradiol and levels of sex hormone-binding globulin or dehydroepiandrosterone sulfate during puberty. We conclude that the nocturnal rise in gonadotropin secretion during puberty in girls is accompanied by an increased secretion of 17 beta-estradiol in the morning. This diurnal rhythm is lost 1 yr after menarche. Determination of 17 beta-estradiol levels in the morning could be useful in determining the initiation of puberty, whereas determinations in the late evening could provide information on the tempo of puberty.