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-beta-estradiol (E2) administration. Our purpose was to study the effects of E2 administration upon substrate metabolism during 90min 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 (100 microg.d(-1) x 3.5d --> 200 microg.d(-1) x 3.5 d --> 300 microg.d(-1) x 4.0 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 plasma E2 (168.1 327.3 pmol.L(-1), P < 0.002). Therewere 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 = 262.4 mmol.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.