Because the SHBG is high, often the bioavailable or active form of testosterone is low, and the female patient often has low libido when on estrogen and even being off of it for a period of time.
SHBG is not affected by transdermal estrogen such as Estrogel or an estradiol patch. It appears that oral progesterone such as Prometrium or Provera may also raise SHBG, although this is probably to a lesser degree than oral estrogen.
SHBG also binds to estradiol and therefore, a high SHBG coupled with a normal estradiol maymean that the amount of bioavailable estradiol is actually on the low side, and a low SHBG may mean a higher bioavailable estradiol. Because of the wide range of estradiol, this is often less important than for testosterone.
Dr. Friedman frequently is trying to figure out whether the patient has hypopituitarism, polycystic ovarian syndrome, or Cushing's syndrome. All these conditions can lead to acne and hirsutism. However, the testosterone is usually high in polycystic ovarian syndrome, especially the bioavailable testosterone, while it is usually low in Cushing's syndrome or hypopituitarism.
Dr. Friedman recently published a paper that a testosterone level above 31 ng/dL (done at Esoterix) is more indicative of polycystic ovarian syndrome, and less than that is more indicative of Cushing's syndrome. If the testosterone is measured in other labs, different cut-offs will be needed.
In conclusion, it is very important to measure bioavailable and total testosterone as well as SHBG in most women being evaluated for hormonal disorders. Dr. Friedman encourages patients to visit his website at www.goodhormonehealth.com for more information.