Effects of glucocorticoid on body growth and serum levels of somatomedin A in the rat.

Serum levels of somatomedin A, as measured by radioreceptor assay, and body weight gain were 86.5 +/- 9.2% and 166.9 +/- 7.8% (N = 5) of the initial values, respectively, after 18 days administration of 2.5 mg cortisone acetate (CA). These values were significantly lower than those for saline treated rats (P less than 0.005). Reduced serum somatomedin A and body growth rate were partially restored after halting the injection of CA. Combined administration of daily doses of 100 micrograms hGH with CA did not prevent the decrease in somatomedin activity in treated rats. This observation suggests that GH plays a minor (or no) role in the fall of serum somatomedin A in CA-treated rats. From these data we conclude that glucocorticoids reduce serum somatomedin by inhibiting the effect of GH on the generation of somatomedin.