The relationship between libido and testosterone levels in aging men

Context: 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. Objective: Our objective was to assess the strength and significance of the association between aging men's self-reports of libido and serum T concentrations. Design: 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. Setting: We conducted an epidemiological study in greater Boston, Massachusetts. Participants: 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). Main Outcome Measures: We assessed total and calculated bioavailable T. Results: 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. Conclusions: 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.