But clinical hypogonadism is real, doctors say, and testosterone replacement is an approved treatment.
"If you're already on testosterone and have found benefit, it's reasonable to continue," Spitzer said. Men who have concerns, he added, should talk to their doctor -- and not just abandon the therapy because of these findings.
The study was funded by the U.S. National Institute of Child Health and Human Development. Auxilium Pharmaceuticals provided the testosterone gel, and Pfizer supplied the Viagra.
Learn more about erectile dysfunction from the U.S. National Institute of Diabetes and Digestive and Kidney Diseases.
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