The relationship between libido and testosterone levels in aging men.

Abstract

Although it is known that serum testosterone (T) concentrations are related to libido, the strength of that relationship in community-dwelling men has not yet been determined. Our objective was to assess the strength and significance of the association between aging men's self-reports of libido and serum T concentrations. Our study was a community-based evaluation of men's health and aging, including three data collection waves: baseline (T1, 1987-1989) and follow-ups (T2, 1995-1997; T3, 2002-2004). Libido was measured on a 14-point scale assessing self-reported frequency of desire and thoughts/fantasies; low libido was defined as a score of less than 7 of 14. We conducted an epidemiological study in greater Boston, Massachusetts. There were 1632 men aged 40-70 yr at baseline, with follow-up on 922 (56%) at 9 yr (T2) and 623 (38%) at 15 yr (T3). We assessed total and calculated bioavailable T . Three hundred eighteen (19%) subjects reported low libido at baseline. Libido and T displayed a significant association. However, the difference in mean T levels between those subjects with low libido and those without was small; analyses indicated a 3.4 ng/dl (0.12 nmol/liter) increase in total T per unit increase in libido. Subjects reporting low libido exhibited an increased but modest probability of exhibiting low T. Dividing T concentrations by the number of androgen receptor gene cytosine, adenine, guanine repeats did not enhance associations. Libido and T concentrations are strongly related at the population level. However, the value of individual patient reports of reduced libido as indicators of low T levels is open to question.