The heptapeptide growth hormone-releasing peptide-1 (GHRP-1 ), one of a series of recently synthesized small growth hormone (GH)-releasing peptides, was administered as an iv bolus (1 μg/kg) to 15 (six prepubertal, nine pubertal) short but healthy children and adolescents and to eight juvenile patients with pituitary insufficiency (four with isolated growth hormone deficiency, two with multiple pituitary hormone deficiencies, one with partial GH deficiency and one with GH-releasing hormone (GHRH) deficiency). Eleven out of 23 subjects also underwent an iv GHRH (1–29) test (1 μg/kg). All the healthy children responded with a progressive rise in plasma human GH (hGH) peaking at 15–30 min, with a significantly higher rise (p<0.05) in the pubertal than prepubertal group. The hGH response to GHRH (1–29) in these children was similar or slightly higher. Six hypopituitary patients had no response to either GHRP-1 or GHRH; the patient with partial GH deficiency had a hGH peak of 6.5 μg/l (at 5 min) to GHRP-1 and 9.2 μg/l (at 1 5 min) to GHRH. One patient had no response of hGH to hypoglycemia, clonidine and GHRP-1, but the plasma hGH rose to 10 μg/l after GHRH. Following the GHRP-1 bolus there was a significant (p <0.01) rise in plasma free thyroxine and a decrease of thyrotropin (p <0.01), both in the limits of normal values. There was also a transitory rise of plasma cortisol (p <0.05). Plasma prolactin, luteinizing hormone and follicle-stimulating hormone did not change. It is concluded that GHRP-1 is a potent GH-releasing drug because it acts also when administered orally and has great pharmaceutical and clinical applications.
Bone mineral density and bone turnover markers in patients on long-term suppressive levothyroxine therapy for differentiated thyroid cancer
