Responses of serum GH and somatomedin-C to an analogue of GHRH in children with growth hormone deficiency

摘要

Twenty-seven children and young adults with growth hormone deficiency (GHD) were given an i.v bolus of 200 ug of either GHRH(1-40) or of a shorter analogue of growth hormone-releasing hormone, GHRH(1-29)NH2; serum GH and somatomedin-C levels were measured. Thirteen showed a significant rise in serum GH, including 3 patients with hypothalamic tumours, 7 with idiopathic isolated GHD or panhypopituitarism and 3 children cranially-irradiated for non-endocrine tumours. A poor response was seen in patients with isolated GHD who had been on long-term therapy. Four patients given a second dose of 500 ug GHRH(1-29)NH2 two hours after the first dose showed little response to this second dose. Long-term (8-24 hr) i.v infusion of GHRH(1-29)NH2 demonstrated pulsatile GH secretions with no evidence of priming or down-regulation. Somatomedin-C levels, when measured, rose in parallel to serum GH, and often became normal. It is concluded (i) that children with idiopathic GHD, hypothalamic tumours, and cranial irradiation may have a defect in the synthesis or delivery of endogenous GHRH; (ii) GHRH(1-29)NH2 is a useful test for pituitary GH reserve in such patients; (iii) GHRH(1-29)NH2 may have long-term therapeutic potential.