What is the prevalence of hypogonadism in older men?
The prevalence of male hypogonadism is not completely known because of the lack of consensus on the definition of hypogonadism with aging. When using a biochemical definition of hypogonadism of serum total testosterone concentrations < 325 ng/dL, the Baltimore Longitudinal Study of Aging reported increased hypogonadism prevalence rates with advancing age of 12%, 19%, 28%, and 49% of men in their 50s, 60s, 70s, and 80s, respectively. However, the prevalence of symptomatic hypogonadism in this study was not reported. When hypogonadism was defined as total testosterone < 300 ng/dL and free testosterone < 5 ng/dL, almost 50% of men aged > 50 years with hypogonadism were asymptomatic, whereas 65% of men with symptoms had normal testosterone levels. The prevalence of symptomatic androgen deficiency is estimated to be at least 5% in men aged 50 to 70 years and 18% in older men. In 2018, the Endocrine Society published updated testosterone therapy guidelines and recommended that hypogonadism be diagnosed in men with signs and symptoms of testosterone deficiency (e.g., low libido, loss of body hair, hot flushes, decreased energy) and unequivocally and consistently low morning serum testosterone concentrations. It is important to note that defining hypogonadism can be challenging because symptoms can be variable, nonspecific, and influenced by age and other factors (e.g., obesity). Additionally, it is important to confirm low testosterone concentrations because of large day-to-day variability in serum levels. Indeed, 30% of men with an initial testosterone value in the hypogonadal range have a normal serum testosterone level on repeat measures. Serum testosterone has diurnal variation and can be influenced by food and exercise; thus, serum measures should occur in the morning after an overnight fast and abstinence from exercise.