Growth hormone (GH) response to GH-releasing hormone in short children: lack of correlation with endogenous nocturnal GH secretion.

The growth hormone (GH) response to iv administration of GH-releasing hormone (GHRH, 0.3 microgram/Kg) was evaluated in 21 short children (13 boys and 8 girls, age 6.7-13.8 yr). Fourteen had familial short stature and/or constitutional growth delay, one had coeliac disease, and 6 were ultimately diagnosed as non-classical GH deficiency or neurosecretory dysfunction on the basis of subnormal integrated spontaneous GH concentrations (ICGH). The response was compared with 12-h spontaneous GH secretion measured every 30 min from 20:00 to 08:00. Mean ICGH ranged from 2.0-17.7 micrograms/l, with a maximum nocturnal GH peak ranging from 5.4-74 micrograms/l. The maximum GH peak after GHRH ranged from 9.4-50 micrograms/l, and the area under the curve (AUC) from 406-3012 micrograms.min/l. No correlation was found between the maximum GH peak and the AUC after GHRH and the maximum overnight GH peak, the ICGH and the overnight AUC. This study confirms that the GH response to GHRH is highly variable among short children with a wide range of spontaneous GH secretion, and that this response is not correlated with the spontaneous ability to secrete GH.