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 % V˙O₂peak in 11 healthy, young males. E₂ was administered in a single-blind, cross-over, randomized fashion for 11 d (100 μg · d^{- 1} × 3.5 d → 200 μg · d^{- 1} × 3.5 d → 300 μg ·d^{- 1} × 4.0 d). Respiratory exchange ratio (RER), V˙O₂, 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). 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 = 262.4 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.

Key words:

Glycogen, estrogen, sex differences, testosterone.

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