Daytime pulsatile growth hormone secretion during childhood and adolescence

Spontaneous GH secretory patterns were studied in 91 subjects (84 children, 2-18 yr old, at various stages of pubertal development and 7 healthy adults). Plasma GH was determined every 20 min for 6 h (0900-1500 h), and at least 1 spontaneous GH secretory episode (peak, greater than or equal to 5 ng/ml) was evident in 61 children and 5 of 7 adults. There was no significant difference in the mean number of GH secretory episodes or the mean 6-h plasma GH levels in 40 children with short stature compared to those in children of the same sex and pubertal maturation with normal or tall stature. The mean number of GH secretory episodes observed during the sampling period was significantly less in Tanner Stage II males (1.3 +/- 0.15) than in Tanner Stage III males (2.1 +/- 0.20; P less than 0.05). Also, the mean 6-h plasma GH level and the amplitude of the highest GH peak in Tanner Stage III (or greater) boys were greater than those in the prepubertal, early pubertal, or adult male subjects. Among females there was no difference in the number of peaks, mean 6-h plasma GH, or mean peak amplitude in prepubertal, pubertal, or adult subjects. Furthermore, there was no significant difference in overall mean 6-h plasma GH levels between male and female subjects. The frequency of GH secretory bursts was greater between 0830-0930 and 1330-1430 h. The GH secretory profiles were not different in children fed 1 or 2 meals. Children failing to show spontaneous peaks had GH deficiency secondary to central nervous system pathology (n = 10), psychosocial GH deficiency (n = 4), estrogen-dependent GH deficiency (n = 2), and optic nerve hypoplasia (n = 3). There were 2 false negatives and 2 children who were not retested. Pulsatile GH secretion is present during the daytime in children of all ages and stages of puberty. Determination of spontaneous GH secretory bursts is a safe and effective method for assessing GH deficiency.