While there's a statistical link between men's sex drive and their testosterone levels, in practice there's little meaningful difference in testosterone levels between men with low libido and those with high libido, researchers report.

Dr. Thomas G. Travison, from the New England Research Institutes in Watertown, Massachusetts, and his associates evaluated data from the Massachusetts Male Aging Study, and report their findings in the Journal of Clinical Endocrinology and Metabolism.

Between 1987 and 1989, a total of 1632 men ages 40 to 70 years were enrolled in the study. They were assessed at the outset and two more times approximately 9 and 15 years later, when 922 and 623 men, respectively, were available.

At each time point, the men completed a self-administered questionnaire asking about the frequency of sexual desire and of sexual thoughts and fantasies, and their hormone levels were measured.

Men with scores of less than 7 points out of a total 14 were classified as having a low libido, which included 19 percent of men at the start of the study, 23 percent after 9 years, and 28 percent at 15 years.

Travison's team reports that, overall, libido was significantly associated with testosterone levels. However, the difference in testosterone levels between participants with low libido and those with high libido was small and "inconsequential."

Looked at the other way, a low libido did not mean a man was particularly likely to have low levels of testosterone.

Therefore, the researchers conclude that if a man complains of reduced libido, it cannot always be interpreted as a sign of testosterone deficiency.

SOURCE: Journal of Clinical Endocrinology and Metabolism, July 2006.