Comparación de distintos métodos para evaluar la función androgénica en el adulto mayor / Assessment of androgenic decline in the elderly

ABSTRACT

Background:The gold standard to assess androgenic status is the measurement of free testosterone by equilibrium dialysis. However, the estimation of free testosterone using formulas based on the law of mass action can be an adequate standard. Aim: To assess androgenic decline in the elderly by different methods. Material and methods: Free testosterone by radioimmunoassay, total testosterone and steroid binding globulin (SHBG) by automated chemiluminiscence system and estradiol by automated electrochemiluminiscence system were measured in 30 male aged 64±5 years (range 60-70), and 25 males aged between 20 and 30 years, as control group; devoid of diseases or drugs that could cause hypogonadism. Free androgen index, free testosterone, biavailable testosterone, and free estradiol were calculated using a formula based on the law of mass action. Results: Fifty seven percent of elderly subjects had hypogonadism, according to calculated free testosterone values. Their total testosterone was on average, 152 nd/dl lower than in young adults, figure that represents a 3.8 ng/dl decline per year. According to total testosterone values, 27 percent of elderly males had gonadal incompetence. The correlations between calculated free testosterone and total testosterone was 0,95 and between calculated free testosterone and measured free testosterone was 0,67. The methods employed overestimated (76.7 percent of hypogonadism when using the free androgen index) or underestimated (27 and 3 percent of hypogonadism, considering total or free testosterone, respectively) the ondrogen decline of the elderly. Among the elderly, 16 or 30 percent of subjects had an absolute hypoestrogenism, based on estradiol or calculated free estradiol values, respectively. On average there was a 20 and 30 percent reduction of estradiol and calculated free estradiol values in the elderly. Conclusions: Calculated free or bioavailable testosterone values should be used to assess androgen decline in elderly men.