Short-term 17-β-estradiol administration does not affect metabolism in young males

We have previously demonstrated that females oxidize more lipid and less protein and carbohydrate during endurance exercise [21]. Several studies in male rats have demonstrated similar metabolic changes after 4 d of 17-β-estradiol (E₂) administration. Our purpose was to study the effects of E₂ administration upon substrate metabolism during 90 min of cycle ergometry at 60% VO₂peak in 11 healthy, young males. E₂ was administered in a single-blind, cross-over, randomized fashion for 11 d (100μg·^.1x3.5d→200μg·d^.1 x3.5d→300μg· d^.1x4.0 d). Respiratory exchange ratio (RER), VO₂, Ve, HR, lactate, and glucose were measured every 30 min during exercise and E₂, testosterone TEST, glycerol and triglycerides were measured prior to exercise T = 0 min. Muscle biopsies were taken from the vastus lateralis before and after exercise for glycogen determination. Estradiol treatment resulted in lower plasma TEST (20.8→7.8 nmol·L^-1, P<0.0001) and higher plas E² (168.1→327.3 pmol·L^-1, P<0.002). There were no effects of E₂ treatment upon any of the other measured variables including muscle glycogen: (E₂-PRE=529.3→POST=237.9; PL-PRE=582.2→POST=262.4mmol·kg^.1[dm]). We concluded that short-term E₂ treatment increased plasma _E2 to female follicular levels in males but had no effect upon lipid or carbohydrate metabolism.