Document Detail

No effect of short-term testosterone manipulation on exercise substrate metabolism in men.
MedLine Citation:
PMID:  15994239     Owner:  NLM     Status:  MEDLINE    
Compared with women, men use proportionately more carbohydrate and less fat during exercise at the same relative intensity. Estrogen and progesterone have potent effects on substrate use during exercise in women, but the role of testosterone (T) in mediating substrate use is unknown. The purpose of this investigation was to assess how large variations in the concentration of blood T would impact substrate use during exercise in men. Nine healthy, active men were studied in three distinct hormonal conditions: physiological T (no intervention), low T (pharmacological suppression of endogenous T with a gonadotrophin-releasing hormone antagonist), and high T (supplementation with transdermal T). Total carbohydrate oxidation, blood glucose rate of disappearance, and estimated muscle glycogen use were assessed by using stable isotope dilution and indirect calorimetry at rest and while bicycling at approximately 60% of peak O2 consumption for 90 min. Relative to the physiological condition (T = 5.5 +/- 0.5 ng/ml), total plasma T was considerably suppressed in low T (0.8 +/- 0.1) and elevated in high T (10.9 +/- 1.1). Despite the large changes in plasma T, carbohydrate oxidation, glucose rate of disappearance, and estimated muscle glycogen use were very similar across the three conditions. There were also no differences in plasma concentrations of glucose, insulin, lactate, or free fatty acids. Plasma estradiol (E) concentrations were elevated in high T, but correlations between substrate use and plasma concentrations of T, E, or the T-to-E ratio were very weak (r2 < 0.20). In conclusion, unlike the effect of acute elevation in E to constrain carbohydrate use in women, acute changes in circulating T concentrations do not appear to alter substrate use during exercise in men.
Barry Braun; Laura Gerson; Todd Hagobian; Daniel Grow; Stuart R Chipkin
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Publication Detail:
Type:  Clinical Trial; Journal Article; Research Support, Non-U.S. Gov't     Date:  2005-06-30
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  99     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2005 Nov 
Date Detail:
Created Date:  2005-10-17     Completed Date:  2005-12-14     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1930-7     Citation Subset:  IM    
Department of Exercise Science, 106 Totman Bldg., University of Massachusetts, Amherst, MA 01003, USA.
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MeSH Terms
Androgens / administration & dosage*
Blood Glucose / metabolism
Energy Metabolism / drug effects*,  physiology
Exercise / physiology*
Glycogen / metabolism
Gonadotropin-Releasing Hormone / administration & dosage,  analogs & derivatives
Heart Rate / physiology
Hormone Antagonists / administration & dosage
Lipid Peroxidation / drug effects,  physiology
Oxygen Consumption / drug effects,  physiology
Pulmonary Gas Exchange
Testosterone / administration & dosage*,  antagonists & inhibitors*
Reg. No./Substance:
0/Androgens; 0/Blood Glucose; 0/Hormone Antagonists; 33515-09-2/Gonadotropin-Releasing Hormone; 58-22-0/Testosterone; 9005-79-2/Glycogen; OON1HFZ4BA/cetrorelix

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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