Effects of oral testosterone undecanoate on growth, body composition, strength and energy expenditure of adolescent boys

OBJECTIVE: We determined the effect of 3 months of daily, 40 mg oral testosterone undecanoate on growth, body composition, hand grip and quadriceps muscle strength, and total free-living daily energy expenditure in boys with constitutionally delayed puberty. DESIGN: Double blind, placebo controlled study. PATIENTS: Eighteen boys with constitutionally delayed puberty, mean (SD) age 13.2 (1.6) years. MEASUREMENTS: Body composition measurements were made by skinfold thickness, bioelectrical impedance and stable isotope dilution (H2(18)O) methods. Energy expenditure was assessed by the doubly-labelled water (2H2(18)O) technique. RESULTS: Height velocity increased from 5.4 (0.8) to 8.1 (0.6) cm/year (P < 0.05) in the 3 months after active therapy. Fat-free mass increased more with therapy (2.7 (0.3) kg) over the 6-month study period than with placebo (1.7 (0.4) kg, P < 0.5). Height velocity increases correlated with daily increases in fat-free mass (r = 0.68, P = 0.005) in the study group as a whole. Energy expenditure and muscle strength increased similarly in both groups. Predicted adult height decreased in the group which was treated with testosterone undecanoate. CONCLUSIONS: Testosterone undecanoate (40 mg daily for 3 months) significantly increased height velocity and fat-free mass velocities after 6 months but not muscle strength, endurance or total daily energy expenditure.