Measuring gonadotropins is of limited value in detecting hypogonadism in ageing men: the Tromsø study

Testosterone levels decrease with age. The mechanisms responsible for the age-related decrease in testosterone concentration are still being debated, and probably involve all three levels of the hypothalamo-pituitary-testicular axis. Luteinizing hormone (LH) concentration is often measured in combination with testosterone, but its value is questionable when considering the testosterone levels of older men. The objective of the present study was to examine the associations of endogenous gonadotropin and testosterone levels both in a cross-sectional cohort of 3447 men participating in the fifth Tromsø study and longitudinally in a cohort of 1352 men participating in both the fourth and the fifth Tromsø study. Total testosterone, LH, follicle-stimulating hormone and sex hormone-binding globulin levels were measured with immunoassay while free testosterone levels were calculated. Total testosterone and LH were independently and positively associated in the cross-sectional analyses (p < 0.001). In the longitudinal study, however, LH levels did not predict changes in total and free testosterone levels. Thus, in clinical practice, measuring gonadotropins seems to be of limited value in detecting hypogonadism in ageing men.