Hypoandrogenaemia is associated with subclinical hypothyroidism in men

Hypothyroidism has been shown to be associated with a reduction in serum testosterone level in males. This reduction in testosterone is reversible by thyroxine replacement therapy. However, to the best of our knowledge, it is not yet known, whether a similar reduction in serum testosterone level is observed in subclinically hypothyroid males [thyroid-stimulating hormone (TSH) < 10 mIU/L] in whom the benefits of thyroxine replacement therapy are still controversial. Our goal was to investigate the putative connections between subclinical hypothyroidism and the circulating levels of gonadotrophins and gonadal steroids in males (mean age +/- SEM, 34.67 +/- 1.52 years; ranging from 20 to 54 years). The serum samples from patients showing normal euthyroid and subclinical hypothyroid profiles (TSH < 10 mIU/L) were further analysed for the levels of luteinizing hormone, follicle-stimulating hormone, prolactin, testosterone, sex hormone-binding globulin, progesterone and oestradiol. Subclinical hypothyroidism was associated with a decrease in the levels of serum testosterone and its precursor progesterone. The data suggest that serum testosterone declines because of the non-availability of its precursor progesterone. The level of oestradiol was similar in both the groups, suggesting a greater conversion rate of testosterone to oestradiol in subclinically hypothyroid males, in order to maintain the oestradiol levels. Prolactin levels were slightly but significantly increased in subclinical hypothyroidism. To the best of our information this is a novel report, which shows a direct association between subclinical hypothyroidism and hypoandrogenaemia. Testosterone deficiency and its symptoms should be kept in view while managing subclinical hypothyroidism in male patients. Further studies are needed in order to reveal the physiological and molecular mechanisms leading to hypoandrogenaemia in subclinical hypothyroidism (TSH < 10 mIU/L).