Overweight in turner syndrome: influence on growth hormone secretion and treatment

The role of growth hormone (GH) in short stature associated with Turner syndrome (TS) is still unclear. Recently it has been suggested that overweight in TS can decrease nocturnal GH secretion and the response to GHRH stimulation test as in idiopathic obese subjects. The aim of this study was to determine the relationship between obesity, stimulated growth hormone secretion and the response to GH treatment in TS. The degree of overweight in 30 TS girls (aged 3.1-14.4 years) was correlated with the response to various GH stimulation tests (GHRH, L-DOPA, arginine, clonidine and propranolol-glucagon (PGST) and with linear growth rate during six months of GH treatment (0.6 U/kg/week). GH secretion evaluated as peak (P) and as area under curve (AUC) after GHRH was negatively correlated with the degree of adiposity expressed as % of ideal body weight (IBW) (P:r = -0.52, p < 0.03; AUC:r = -0.58, p < 0.01) and as body mass index (BMI) (P:r = -0.54; p < 0.02; AUC:r = -0.60, p < 0.01); no correlation was found between the other tests and overweight. Furthermore GH response to GHRH was significantly reduced in obese (% IBW > 120) versus non obese patients as P (p < 0.04) and as AUC (p < 0.05); this trend was also observed after PGST (p < 0.05) but not after the other tests. After GH treatment growth velocity similarly increased in obese and non obese TS girls. No correlation was found between GH secretion and the increase in growth velocity after GH treatment. Our data confirm that overweight may be responsible for a blunted GH secretion in TS; however, it does not affect the response to GH therapy.