In obese male subjects with 160 - 200% of ideal body weight (IBW = 100%) the decrease in total plasma
testosterone is biologically ineffective since SHBG is concomitantly decreased from 30.0 +/- 3.6 to 20.0 +/- 3.4 nM/l. Conversely, in massively obese males with greater than 250% of IBW, the decrease in SHBG (to 10.6 +/- 1.8 nM/l) is too small to compensate for total
testosterone decrease (from 6.04 +/- 0.57 to 1.72 +/- 0.32 ng/Ml). Therefore, free
testosterone is markedly less in the massively obese patients (55 +/- 8 vs. 127 +/- 15 pg/ml in the controls). Despite this significant difference in free
testosterone concentrations (p less than 0.01), plasma LH is even lower in the obese (6.8 +/- 0.8 mU/ml) than in the controls (10.0 +/- 1.0 mU/ml). This may be an effect of free
estradiol, which rises from 0.48 to 1.52 pg/ml in the massively obese subjects. These alterations are clearly demonstrated by the imbalance of the
estradiol/
testosterone ratios, which increase 10-fold and 7-fold for the total and for the free
sex hormones, respectively. We conclude that the decrease in SHBG, which prevents obese males from developing
hypogonadism, is not sufficiently effective in the massively obese patients to compensate the marked decrease in
testosterone. This, in connection with the observed increase of free
estradiol, may cause
hypogonadism and hyperestrogenism in these subjects.