SHBG and hyperthyroidism: Clinical studies have demonstrated that thyroid hormones (T3 and T4) directly regulate ovarian sex hormone synthesis and metabolism: patients with hyperthyroidism exhibit a two- to three-fold increase in total estrogen levels accompanied by markedly elevated sex SHBG levels, resulting in reduced free testosterone fractions, whereas hypothyroidism reduces SHBG levels, leading to decreased total estrogen and testosterone levels but elevated free hormone fractions.