TESTOSTERONE ADMINISTRATION INCREASES INSULIN-LIKE GROWTH FACTOR-I LEVELS IN NORMAL MEN

Although testosterone (T) administration can increase insulin-like gro wth factor-I (IGF-1) when administered to hypogonadal men, no studies have examined whether this occurs in normal men. The present study was undertaken to determine if an increase in IGF-I may be part of the an abolic effect of androgens. We enrolled 11 normal men in a randomized, double-blinded cross-over study. Subjects were assigned to receive ei ther T enanthate (TE) (300 mg im, each week) or nandrolone (ND) decano ate (300 mg im, each week) for 6 weeks. After a washout period subject s were administered the alternate treatment. Pre- and posttreatment se rum was analyzed for IGF-I by RIA after acid-ethanol extraction. Resul ts expressed as mean +/- SEM (Table 1). IGF-binding protein-3 was meas ured by RIA and was unchanged in the TE treatment and decreased signif icantly after ND treatment, Although GH levels were not significantly different after either TE or ND treatment, they tended to increase aft er TE treatment (1.23 +/- 0.28 ng/mL vs. 3.3 +/- 1.03 ng/mL) but remai ned unchanged after ND treatment (1.68 +/- 0.68 ng/mL vs. 1.89 +/- 0.6 4 ng/mL). Serum total T levels increased 32 +/- 0.05 nmol/L in the TE- treated men, but fell by 7 +/- 0.02 nmol/L in the ND-treated men (P < 0.0001). Serum estradiol levels rose by 193.04 +/- 19.82 pmol/L in the TE-treated men although falling by 50.65 +/- 34.50 pmol/L in the ND-t reated men (P < 0.0002). These data indicate that when normal men are given TE, serum IGF-I levels increase after 6 weeks of treatment. Trea tment with ND did not change serum levels of IGF-I but did decrease th e level of the major serum IGF-BP and therefore the level of bioavaila ble IGF-I may be increased in the ND group.