Reduced growth hormone secretion in turner syndrome: Is body weight a key factor?

The age-related decline in spontaneous growth hormone (GH) secretion has been suggested to cause growth failure in girls with Turner syndrome (TS). We studied 23 girls (mean age ± SD: 11.1 ± 2.7 years) diagnosed to have TS by karyotype analysis. The control group consisted of 18 prepubertal age- matched subjects (10.7 ± 2.5 years) with growth retardation due to familial short stature and/or constitutional growth delay. In addition, 18 children (10.9 ± 3.3 years) diagnosed to have GH deficiency by two different provocative tests were chosen as a further comparison group. Spontaneous 12-hour nocturnal GH secretion was assessed by RIA at 30-min intervals. Plasma insulin-like growth factor 1 (IGF-1) levels were determined by RIA after acid-ethanol extraction. Girls with TS had a percentage of ideal body weight significantly higher than controls (p < 0.0001) and showed spontaneous GH secretion significantly lower than controls (mean ± SD: 3.2 ± 1.6 in TS vs. 5.5 ± 1.3 μg/l in controls; p < 0.0001) but higher than GH-deficient patients (1.3 ± 0.8 μg/1; p < 0.0001). No significant difference was found in IGF-1 levels between TS patients and controls, whereas GH-deficient children showed IGF-1 levels significantly lower than those of TS patients (p < 0.0005). As expected, GH concentrations correlated with bone age in controls (r = 0.51, p < 0.05), whereas no relationship was seen in TS. Interestingly, in TS, GH levels were negatively related to the percentage of ideal body weight (r = -0.43, p < 0.05). The finding of GH levels intermediate between control and GH-deficient patients together with normal IGF-1 concentrations, questions the existence of a ‘classical’ GH insufficiency in TS girls. This study confirms that weight excess is a common feature of TS girls at pubertal age and suggests that the reduced GH secretion might be due, at least in part, to obesity.