A boy with "transient" growth hormone deficiency in prepubertal stage despite normal growth hormone secretion in childhood and after puberty.

Transient growth hormone deficiency (GHD) is occasionally found in prepubertal individuals, and this phenomenon has been variously interpreted. Sex steroids enhance GH secretion; however, the cut-off values of provocative GH tests are not modified according to the physiological changes. Physiological changes in sex steroid levels are thought to cause the image of transient GHD. In addition, the reproducibility of provocative GH tests makes the interpretation complicated. We experienced a case of a boy with short stature who had undergone provocative GH tests at three different times: childhood (5 and 7 years old), before puberty (12 years old), and in adolescence (15 years old). Although the responses of GH in his childhood and adolescence were within the normal range, his prepubertal GH response was extremely low, as if he had "complete" GHD (peak GH: insulin test, 0.60 ng/ml; clonidine test, 0.78 ng/ml). No morphological changes were observed in the pituitary gland or hypothalamus on MRI. The level of insulin-like growth factor 1 was in the normal range for his age at this time. Here, we report the clinical course and endocrinological data of this case, and suggest that transient GHD is caused not only by the physiological effects of sex steroids but also by certain mechanisms that actively reduce GH secretion.