Primary hyperparathyroidism is associated with marked impairment of GH response to acylated ghrelin

Abstract

Background: Impaired GH secretion is a common finding in patients with primary hyperparathyroidism (PHP). Ghrelin displays strong GH-releasing action, mainly at the hypothalamic level. Objective: To evaluate secretory response of GH to ghrelin in PHP patients. Patients: Fifteen patients [11 women/4 men, mean age 54 years, range 32-70 years, body mass index (BMI) 25.0 ± 0.7 kg/m2] affected with PHP due to single parathyroid adenoma and 35 normal age-matched subjects (23 women/12 men, mean age 58 years, range 35-68 years, BMI 24.1 ± 1.1 kg/m2). Methods: A measure of 1 μg/kg body weight i.v. acylated ghrelin or 1 μg/kg body weight i.v. GH releasing hormone (GHRH) followed by 0.5 g/kg body weight i.v. arginine (ARG) hydrochloride were administered to all subjects on alternate days in order to evaluate GH response. Results: Mean serum GH peak after GHRH + ARG was 32.6 ± 7.8 and 17.4 ± 4.0 μg/l, in controls and PHP patients, respectively (P < 0.05). Mean serum GH peak after ghrelin was 70.4 ± 31.5 and 16.8 ± 1.9 μg/l, in controls and PHP patients, respectively, (P < 0.001). Using ROC curves, a serum GH peak > 22 μg/l after ghrelin stimulation might be considered as a cut-off value for identifying normal subjects. Ten (67%) PHP patients have impaired GH response to GHRH + ARG and 13 (87%) to ghrelin. Serum GH peak after ghrelin or GHRH + ARG was unrelated to serum IGF-1, PTH or ionized calcium concentrations. Conclusions: The present data confirm that GH secretion is impaired in PHP patients using the potent GH secretagogue ghrelin and suggest that impaired GH secretion is likely due to a deleterious effect of hypercalcaemia at the hypothalamic level in PHP patients. © 2008 The Authors.