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).