If you have a patient with amenorrhea, one possible cause is hyperthyroidism. Thyroid hormones will increase the expression of SHBG, thus enhancing estradiol, then estradiol increases LH (and disturbs its cyclical pattern) and produce amenorrhea.
However, if a patient has polycystic ovary syndrome, levels of SHBG are lower (because of high insulin) and free testosterone is higher, leading to hirsutism and anovulatory cycles.
So, if the free hormone is the active hormone, how it comes that higher SHBG levels increase estradiol activity but lower SHBH levels increase androgen activity? Shouldn't they vary in the same direction?
SHBG Affinity varies between testosterone and estrogen almost 20 times higher.
Increase SHBG reduces the bio availability of both testosterone and Estrogen.
In hyperthyroidism, increase SHBG lowers the level of active estrogen and testosterone ( estrogen peak is important for ovulation) which results in amenorrhoea or Anovulatory cycle.
In PCODs lower level of SHBG, increases the level of both estrogen and testosterone. Increase testosterone results in hirsutism and anovulatory cycle. Here affinity of testosterone and Dihydrotestosterone by SHBG was many times higher than estrogen and estradiol. so lower level of SHBG results in more availability of male sex hormone when compared to female sex hormone though both raises.
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