Effect of obesity on endogenous secretion of growth hormone in Turner's syndrome.

Nocturnal growth hormone secretion over a 12 hour period was assessed at 20 minute intervals in 25 prepubertal subjects with Turner's syndrome and 11 normal prepubertal girls of short stature to try and elucidate the relationship between body weight and endogenous secretion of growth hormone in Turner's syndrome. There were no differences in mean growth hormone concentration, age, height, or growth velocity between the two groups. There was an age related decline in mean growth hormone concentration in patient's with Turner's syndrome in contrast to the age related increase in controls. Mean percentage of ideal body weight was significantly higher in the Turner's syndrome group than among controls and it increased with age. There was a strong inverse relationship between mean growth hormone concentration and percentage of ideal body weight in those with Turner's syndrome. Covariate analysis of the multiple linear regression of mean growth hormone concentration on age and percentage of ideal body weight in Turner's syndrome indicated that percentage of ideal body weight had a significant effect on endogenous secretion of growth hormone when age was held constant, but not the other way round. We conclude that the age related decline in endogenous secretion of growth hormone in Turner's syndrome is partly the result of increasing body weight with age. The significant influences of biological variables such as age and body weight in the interpretation of measurements of endogenous secretion of growth hormone in Turner's syndrome should be emphasised.