TESTOSTERONE DECREASE AND OESTROGEN INCREASE IN MALE PATIENTS WITH OBESITY

Abstract

ABSTRACT The concentration of sex hormones and their binding in the plasma were measured in male patients (20–40 years old), who weighed 140–170 % (I), 170–200 % (II) and > 200 % (III) of their ideal weight. Correlated to body weight, there is a reduction in the total concentration of testosterone, which, in the very obese patients, amounts to 41 % (in group I: 85 % in group II: 68 % P < 0.001) of that found in an age-matched healthy control group of subjects of "normal" body weight (90–115 % of the ideal body weight; n: 20). Androstenedione values show only a trend downwards (from 0.94 to 0.72 ng/ml plasma), while the oestrogen values increase significantly; oestrone increases by a factor of 1.09 (I), 1.43 (II; P < 0.001) and 1.69 (III; P < 0.001) and oestradiol by 1.13, 1.43 P < 0.001) and 1.76 (P < 0.001), respectively. Despite the fall in testosterone there are no clinical signs of hypogonadism, as SHBG (from 5.1 ± 0.8 in the controls to 2.4 ± 0.6 ×10−8 Mol/l in the very obese patients of group III) and the protein-bound fraction of testosterone also decrease. As a result the concentration of free testosterone remains constant (120 pg/ml), except in the very obese (93 pg/ml). Because of the different affinity of the binding proteins for testosterone and oestradiol the ratio of free oestradiol: free testosterone shifts less strongly in favour of the feminizing hormone (11.1 × 10−3 in group III as compared to 4.1 × 10−3 in the controls), than is suggested by the total hormone concentrations. A disturbance in the gonadal function of the pituitary gland or the testes is not present, since the concentration of LH is normal and the testicular response to HCG in very obese patients adequate (increase of testosterone by a factor of 3.11 as compared to 2.23 in the controls). The cause of the decrease in testosterone and SHBG is unknown, while the increase of plasma oestrogens is likely to be due to the increased conversion of androgens to oestrogens in the adipose tissue, which clearly plays an important role for plasma concentrations of sex hormones in obese patients.