EFFECTS OF TESTOSTERONE ON BODY-WEIGHT AND ADIPOSE-TISSUE - ROLE OF AROMATIZATION

Treatment of castrated male rats with low doses of testosterone propionate (TP; 0.2 mg/day) increases food intake and body weight gain, but long-term treatment with a higher dose of TP (1 mg/day) reduces body weight gain and carcass fat content. Concurrent treatment with androsta-1,4,6-triene-3,17-dione (ATD), which blocks the aromatization of androgens to estrogens, prevents the weight-reducing effects of high doses of TP. Long-term treatment with 1 mg TP/day also depletes cytoplasmic estrogen receptors and reduces lipoprotein lipase activity in epididymal fat pads. Both of these effects are blocked by concurrent treatment with ATD. In male rats given high doses of TP, estrogenic metabolites of the androgen may reduce body weight gain by direct effects on adipose tissue metabolism, including lipoprotein lipase activity. These mechanisms may underlie the reductions in body weight and carcass fat content seen in gonadally-intact, sexually-active male rats.