GHRH treatment: studies in an animal model.

This study examined the effects of chronic deletion of circulating growth hormone-releasing (GHRH) and/or somatostatin (SRIF) on normal growing male rats, as well as the effects of exogenous GHRH (1-29)NH2 and/or SMS 201-995 administration on the growth of rats with hypothalamic ablation. Passive immunization with anti-rat GHRH goat gamma-globulin (GHRH-Ab) for 3 weeks caused a marked decrease in the levels of pituitary GH mRNA and severe growth failure. Treatment with anti-SRIF goat gamma-globulin (SRIF-Ab) for 3 weeks produced a more modest decrease in GH mRNA levels in the pituitary and a slight but significant inhibition of normal somatic growth. Hypothalamic ablation produced a marked decrease in the level of mRNA in the pituitary. Chronic continuous administration of GHRH (1-29)NH2 stimulated pituitary GH synthesis, elevated serum levels of insulin-like growth factor I and increased body weight gain in rats with hypothalamic ablation treated with replacement doses of cortisone, testosterone and L-thyroxine. Combined treatment with GHRH (1-29)NH2 and SMS 201-995 appeared to promote the effect of GHRH on pituitary GH release and somatic growth in these animals. The results suggest that continuous administration of GHRH will be useful in the treatment of children with growth retardation resulting from hypothalamic disorders. In children with combined GHRH and somatostatin deficiencies, the addition of somatostatin to a GHRH treatment regimen may produce better results.