The effects of sex steroids on ulnar growth during adolescence.

To investigate the relative effects of androgens and estrogens on long bone growth, we evaluated the 3-week ulnar growth velocities of 10 boys before and after the iv administration of testosterone (T; 15 mg/day), dihydrotestosterone (DHT; 7 mg/day), and estradiol (E2; 90 micrograms/day) for 4 days. Ulnar growth is a sensitive index of short term growth in children. Mean 3-week ulnar growth velocities increased from 0.49 +/- 0.11 (+/- SEM) to 1.09 +/- 0.14 mm/3 weeks after the T infusion (P less than 0.005), from 0.42 +/- 0.09 to 0.84 +/- 0.13 mm/3 weeks after the DHT infusion (P less than 0.02), and from 0.67 +/- 0.07 to 0.96 +/- 0.26 mm/3 weeks after the E2 infusion (P = NS). The mean T level was 2555 +/- 234 ng/dl during the T infusion. Mean E2 levels were 53 +/- 4 pg/ml during the T infusion and 102 +/- 7 pg/ml during the E2 infusion. Mean DHT levels were 73 +/- 7 ng/dl during the T infusion and 1115 +/- 124 ng/dl during the DHT infusion. Mean somatomedin-C levels increased to a similar degree during all infusions, but were significantly higher only during the E2 infusion (P less than 0.01). We conclude that T and DHT given for 4 days stimulated ulnar growth, while E2 at concentrations greater than those derived from T did not cause a significant increase in ulnar growth. None of the ulnar growth rates after T, DHT, or E2 treatment, however, differed significantly.