Effects of anabolic-androgenic steroid use or gonadal testosterone suppression on serum leptin concentration in men

Objective: Serum leptin concentration shows a sexual dimorphism that is not accounted for by gender differences in adiposity. A strong inverse associa tion exists between serum leptin and testosterone concentrations in men, po inting to a likely influence of gonadal sex steroids on serum leptin concen tration. The aim of this study was to investigate whether manipulation of s ex steroid hormones in men would alter serum leptin concentration independe ntly of changes in fat mass. Design and methods: The effects of sex steroid suppression on serum leptin concentration were investigated in nine healthy men in whom testosterone ha d been reversibly suppressed for 5 weeks after treatment with intramuscular triptorelin. The effects of sex steroid supplementation were investigated in nine male bodybuilders who self-administered anabolic-androgenic steroid s (AAS) for a mean period of 6.5 weeks. A control group received no hormona l treatment. Results: Testosterone concentration was significantly reduced by triptoreli n administration (7.32 +/- 1.92 ng/ml at baseline compared with 1.15 +/- 0. 57 ng/ml at 5 weeks, P = 0.002), High-dose AAS use was confirmed by urine a nalysis, Body fat percentage was unaffected by the AAS or triptorelin inter vention (P > 0.19). Leptin concentration was significantly reduced after on e cycle of AAS use (2.40 +/- 0.98 ng/ml off cycle compared with 1.63 +/- 0. 37 ng/ml on cycle, P = 0.012), and was significantly increased by triptorel in administration (2.96 +/- 1.50 ng/ml at baseline compared with 6.63 +/- 4 .67 ng/ml at five weeks, P=0.004), No significant change occurred in the co ntrol group. Conclusion: Androgenic sex hormone supplementation decreases serum leptin c oncentration. whereas suppression increases serum leptin concentration, ind ependently of changes in body fat mass in healthy men. The sexual dimorphis m evident in serum leptin concentration is likely to be due to a suppressiv e effect of testosterone on serum leptin concentration in males.