Somatomedin response to testosterone stimulation in children with male pseudohermaphroditism, cryptorchidism, anorchia, or micropenis.

Somatomedin-C (Sm-C) levels increase during puberty. To determine if testosterone could play a role in the pubertal Sm-C increase, 17 boys with low levels of endogenous testosterone (80 ng/dl) were studied before and 7 days after im testosterone treatment. The serum testosterone levels achieved were comparable to those found during normal puberty in most instances. After parenteral testosterone administration, serum somatomedin activity (bioassay) increased in 9 patients (from 10-56% above basal levels) and decreased in 3 (from 3.2-20.3% below basal levels); overall, there was a significant 19.2% increase (P less than 0.02). Testosterone per se did not induce an increase in bioassayable Sm, since its addition to serum failed to cause increments in activity. After im testosterone treatment, serum Sm-C levels (determined by RIA) increased in every patient studied. The mean percent increase above basal levels was 108% (range, 14-202%; n = 10; P less than 0.001). Mean serum GH increased significantly (P less than 0.05) from 4.9 ng/ml before exogenous testosterone to 12.0 ng/ml afterward. The data show that parenteral testosterone administration can increase serum Sm activity and Sm-C, probably through increased pituitary GH secretion, and this response occurs in boys ranging in age from 0.24-14.57 yr.