02 December 2008
The serum levels of insulin-like growth factor I (IGF I), dehydroepiandrosterone sulfate (DHAS), testosterone (T) and estradiol (E2) have been measured in 78 prepubertal and 57 early pubertal patients referred for short stature, at the same time when their secretion of GH was evaluated both during nocturnal sleep and by two conventional stimulation tests. According to the results of GH measurements they were considered as having a normal secretion of GH (group I), a complete GH deficiency (group II), a partial GH deficiency (group III), low responses to stimuli with normal secretion during sleep (group IV) or a nocturnal neurosecretory dysfunction (group V). Though widely scattered, the IGF I levels showed the following characteristics: a significant increase at puberty from 0.77 to 1.29 U/ml (p < 0.001) in the so-called endocrinologically normal patients of group I, not in the other groups; in the prepubertal patients of group I, a correlation of IGF I with chronological age (r = 0.47, p < 0.005) and bone age (r = 0.52, p < 0.002); significantly reduced IGF I levels in patients of group II having complete GH deficiency (p < 0.001); no significant differences between prepubertal patients with partial or atypical GH deficiency from groups III, IV, V and prepubertal patients from group I; lower pubertal levels in groups III, IV, V than in pubertal patients from group I (p < 0.01). The relationships of IGF I with steroids were weak but significantly positive with DHAS in the 78 prepubertal patients (r = 0.36, p < 0.001); positive with the logarithm of T in the early pubertal males (r = 0.31, p < 0.05); negative with the logarithm of E2 in the early pubertal females (r = 0.59, p < 0.06). No correlation with DHAS was found in pubertal patients. There were no correlations between the parameters of GH secretion and the plasma steroids. It may be suggested that before puberty IGF I is modulated in part by DHAS. At the early stages of puberty, in boys T but not DHAS increases the serum levels of IGF I, provided that GH secretion is normal. While in girls, serum E2 correlates negatively with the levels of IGF I. This correlation needs to be confirmed on a larger series of female adolescents.