Why hyperthyroid can cause gynecomastia? what's the connection thyroid hormone and estrogen, testosterone?

3 ways high estrogen: 1) it is thought that high TSH causes increased activity of aromatase which converts free testosterone to estrogen. 2) it is also believed that while both testosterone and estrogen are both increased, high levels of shbg bind free testosterone making Estradiol seem relatively higher 3) increased levels of lh may increase production of testicular estrogens. This results in a net increase in estroge.

Complex interaction: Gynecomastia can occur in hyperthyroidism due to an induced increase in peripheral aromatase activity leading to an increase in circulating estrogen levels, and thus decreased testosterone levels. Most of the estrogen in men is made from the peripheral conversion of testosterone and other androgens to estrogens. Other mechanisms are probably at play as well.