The effect of testosterone on thyroid autoimmunity in euthyroid men with Hashimoto's thyroiditis and low testosterone levels

What is known and objective: Thyroid autoimmune diseases occur much more frequently in women than men. Unfortunately, no previous study has determined whether sex hormones produce any effect on thyroid antibody titres. The primary study aim was to assess whether exogenous testosterone affects thyroid autoimmunity in men with Hashimoto's thyroiditis and low testosterone levels.

Methods: The study population consisted of 34 euthyroid men with autoimmune thyroiditis and testosterone deficiency. On the basis of patient preference, these patients were either treated with oral testosterone undecanoate (120 mg daily; n = 16) or remained untreated (n = 18). Circulating levels of thyrotropin, free thyroxine, free triiodothyronine, prolactin and total testosterone, as well as serum titres of thyroid peroxidase and thyroglobulin antibodies, were measured at the beginning of the study and 6 months later. The structure parameters of thyroid homeostasis (Jostel's thyrotropin index, SPINA-GT and SPINA-GD) were also calculated. Moreover, semen analyses were performed in eight patients in each group.

Results and discussion: In testosterone-naïve men, serum hormone levels and antibody titres remained at the similar levels throughout the study. Apart from increasing serum testosterone levels, testosterone undecanoate reduced titres of thyroid peroxidase and thyroglobulin antibodies and increased SPINA-GT. The drug produced a neutral effect on circulating levels of thyrotropin, free thyroid hormones, prolactin and testosterone, Jostel's thyrotropin index, SPINA-GD and semen parameters. Testosterone-induced changes in antibody titres correlated with the effect of treatment on SPINA-GT and with serum testosterone levels.

What is new and conclusion: This study is the first one to have shown that exogenous testosterone may have a protective effect on thyroid autoimmunity in men with Hashimoto's thyroiditis and testosterone deficiency.