THERAPEUTICAL DOSES OF SALBUTAMOL INHIBIT THE SOMATOTROPIC RESPONSIVENESS TO GROWTH HORMONE-RELEASING HORMONE IN ASTHMATIC CHILDREN

Abstract

Purpose of the Study. To determine the effects of therapeutic β2 agonists (specifically salbutamol) on growth hormone (GH) response to growth hormone releasing hormone (GHRH) in children with asthma. Study Population. Fifteen prepubertal children with asthma, ages 6-11 (average age of 9) with normal or normal short stature were studied. Those with an endocrine abnormality, nutritional deficiency, psychological deprivation, or other systemic disease were excluded. Only those children with known bronchial asthma, who showed a 15% decrease of the 1-second forced expiratory volume (FEV1) with methacholine challenge were included. All patients were asymptomatic, and had not experienced an asthma exacerbation, respiratory infection or allergen exposure in the month preceding the study. No child was on medications. Methods. Subjects were divided into two groups. Both groups had baseline GH response to GHRH determined. After an overnight fast, GH levels were obtained the following morning at -60, 0, and then every 15 minutes until 120 minutes after GHRH administration. Two days following this, Group A received salbutamol (0.125 mg/kg) orally at -60 minutes and GH response to GHRH was remeasured. Group B received aerosolized salbutamol (2 mg over 15 minutes) (details of administration were not specified by the authors). All serum GH levels were measured in duplicate by immunoradiometric assay (sensitivity of 0.1 µg/L). Findings. Basal GH levels were similar in both groups. Orally administered salbutamol (Group A) markedly inhibited GH response to GHRH (peak of 3.7 ± 0.6 vs. 18.6 ± 4.7 g/L). Inhaled salbutamol (Group B), although blunting the GHRH-induced GH response, did so to a lesser extent (peak of 20.0 ± 7.5 vs. 35.8 ± 9.4 g/L, P < .02).