EFFECT OF LOW-DOSE OXANDROLONE AND TESTOSTERONE TREATMENT ON THE PITUITARY-TESTICULAR AND GH AXES IN BOYS WITH CONSTITUTIONAL DELAY OF GROWTH AND PUBERTY

OBJECTIVE To investigate the effect of low dose oxandrolone and testos terone on the pituitary-testicular and GH-IGF-I axes. DESIGN Prospecti ve double-blind placebo-controlled trial. PATIENTS Sixteen boys with c onstitutional delay of growth and puberty (CDGP) with testicular volum es 4-6 ml were randomized to 3 months treatment: Group 1 (n=5), daily placebo: Group 2 (n=5), 2.5 mg oxandrolone daily or Group 3 (n=6), 50 mg testosterone monthly intramuscular injections with assessment (grow th, pubertal development and overnight hormone profiles) at 0, 3, 6 an d 12 months.MAIN OUTCOME MEASURES LH and GH profiles (15-minute sample s) were analysed by peak detection (Pulsar), Fourier transformation an d autocorrelation. Testosterone levels were measured hourly and insuli n, SHBG, IGF-I, and IGFBP-3 levels at 0800 h. Statistical analysis was by multivariate analysis of variance for repeated measures. RESULTS L H and testosterone parameters increased significantly with time in all 16 (LH AUG, P < 0.001; peak amplitude, P = 0.02; number of peaks, P = 0.02; testosterone AUC, P = 0.02; morning testosterone, P = 0.002). I n Group 2, however, LH and testosterone parameters decreased at 3 mont hs followed by a rebound increase at 6 and 12 months. SHBG levels were markedly reduced at 3 months (P = 0.006) and a wider range of dominan t GH frequencies was present although GH AUC was not increased until 6 months, with an increase in GH pulse frequency but not amplitude. IGF -I levels were increased at both 3 and 12 months. In Group 3, pituitar y-testicular suppression was not apparent, but GH levels increased wit h an increase in GH amplitude at 3 and 12 months. CONCLUSION Oxandrolo ne transiently suppressed the pituitary-testicular axis and altered GH pulsatility. Testosterone increased GH via amplitude modulation.