Defective Suppression of Growth Hormone after Oral Glucose Loadin in Adolescence*

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Abstract
The mean (±SEM) zero time serum GH levels in a group of tall girls (3.5 ±0.6 ng/ml) and tall boys (4.1 ±1.2 ng/ ml) did not differ significantly from the mean value (4.3 ± 2.5 ng/ml) in a group of boys with normal stature (P>0.10). Remarkably, 66%of the adolescents tested after menarche or ejacularche showe a defective suppression of GH after glucose loading; the mean serum GH levels at 30 min in the tall girls, tall boys, and normal stature boys exceeded the baseline value by about 6, 13, and 7 ng/ml, respectively. In the girls tested, within 6 months after menarche the incidence of inadequate GH responses (86% was much higher (P < 0.01) than in the girls tested later (38%). I the boys, insufficient data on the exact time of ejacularche were available to justify a similar subdivision.Considering serum alkaline phosphatase (APA) activit as an additional criterion of pubertal development, 80%of the menarchal and ejacularchal adolescents with serum APA levels exceeding 200 U/liter ha defective GH responses compared to 48% of these youngsters with levels less than 200 U/liter (P < 0.01). In 9 of 12 girls and boys tested twice at an earlier and at a later stage after menarche or ejacularche, the defective GH response had disappeared by the later stag Though the data show that this phenomenon regularly occurs in the process of sexual maturation and pubertal active growth, the exact mechanism of the paradoxical GH response in puberty remains unknown. (J Clin Endocrinol Metab51: 265, 1980)