Growth hormone and somatomedin-C in bulimia

Somatomedin-C (SOM-C) concentrations are regulated by circulating growth hormone (GH) concentrations; however, other factors, such as nutrition, also influence SOM-C concentrations. We evaluated the GH-SOM-C axis in seven normal-weight female bulimics one day after hospital admission, and in seven age-, sex-, and weight-matched normal controls. Subjects were medication-free for at least one month. Fasting morning serum GH concentrations were higher in all bulimics (range 2.5-13.3 ng/ml) than in all controls (range less than 1.0-1.8 ng/ml). The mean (+/- SD) maximum GH response to TRH (500 micrograms) was greater in the bulimics (12.9 +/- 4.9 ng/ml) than in the controls (3.7 +/- 2.7 ng/ml) (p less than .001). Despite this GH elevation, the mean (+/- SD) SOM-C concentration was comparable in the bulimics (2.0 +/- 0.6 U/ml) and the controls (1.6 +/- 0.8 U/ml). This suggests that SOM-C generation is resistant to the elevated circulating GH in bulimia and that SOM-C is not inhibiting GH secretion in the pituitary-hypothalamic axis.