Behavior of growth hormone after stimulation with growth hormone releasing hormone (GHRH) in children with disorders of the hypothalamo-hypophyseal axis and girls with Turner syndrome

Abstract

To investigate the hypothalamic pituitary axis in children with various growth disorders stimulation tests with growth hormone releasing hormone (GHRH) were performed and compared to pharmacological stimulation tests. 103 subjects were studied-15 healthy volunteers, 20 patients with isolated growth hormone deficiency (IGHD), 16 patients with multiple pituitary hormone deficiency (MPHD), 17 children with organic growth hormone deficiency (OGHD) and 35 Turner patients. 1 microgram/kg GHRH was administered iv, blood samples were drawn before GHRH and after 5, 15, 30, 45, 60 and 90 minutes. In 53 patients a second GHRH-test was done after repeated GHRH injections (7 times 1 microgram/kg GHRH every 3 hours). In the group of healthy probands we found wide variations of stimulated growth hormone (GH) levels. In 7 of the 20 patients with IGHD the stimulated GH level exceeded 10 ng/ml in one of the two GHRH-tests. The maximal GH response to the second GHRH-test (8.3 +/- 6.8 ng/ml) was significantly higher (p < or = 0.025) than after the first GHRH-test (5.0 +/- 4.0 ng/ml). In patients with MPHD stimulated GH values were significantly lower than in patients with IGHD (p < or = 0.005). GHRH stimulation tests in OWHM patients did not differ from the results in children with IGHD. The GHRH induced GH response in girls with Turner syndrome was significantly lower than in the healthy volunteers (p < or = 0.025). Basal (p < or = 0.05) and GHRH stimulated GH levels (p < 0.02) were lower after estrogen administration. Pituitary GH secretion could be activated by repeated stimulation with GHRH (priming) in children with hypothalamic GH deficiency. Only in the patients with MPHD a correlation could be found between the result of the GHRH-stimulation and one pharmacological GH test. In children with OGHD the radiation dose was negatively correlated to the maximal GH concentrations after L-Dopa stimulation. Basal and GHRH stimulated GH levels in Turner syndrome were lower after estrogen administration.