Thyroid and its Diseases in Breast Cancer

Le résumé fourni par la source

The relationship between thyroid gland function and both the development and growth of mammary gland is better known in thyroid diseases than in normal conditions. A prevalence of gynecomastia as high as 40% has been reported in thyrotoxicosis 1 , 2 and was attributed to the thyroid hormone-driven increased rate of peripheral conversion of androgens to estrogens; 3 another factor could be the enhanced serum levels of sex hormone-binding globulin (SHBG) produced by thyroid hormones. Due to the higher affinity of SHBG for testosterone vs. estrogens, thyroid hormone overproduction will cause, at tissue level, a relative excess of unbound (free) estrogens vs. unbound androgens. However, daily clinical practice shows that there is no evidence of gynecomastia in men treated chronically with thyroid hormones. On the other hand, thyroid failure may also be associated with gynecomastia, probably due to increased prolactin (PRL) release. 4 , 5

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