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; 90μg/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 ± O.11 (± SEM) to 1.09 ± 0.14 mm/3 weeks after the T infusion (P < 0.005), from 0.42± 0.09 to 0.84 ± 0.13 mm/3 weeks after the DHT infusion(P < 0.02), andfrom 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 similardegree during all infusions, but were significantly higher only during theE₂ infusion (P < 0.01). We conclude that T and DHT given for 4 days stimulated ulnar growth, while E₂ at concentrationsgreater 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.