Heal Yourself At Home

Sex Hormone-Binding Carrier Proteins

Sex Hormone Binding Globulin (SHBG)

Corticosteroid Binding Globulin (CBG)

SHBG (sex hormone binding globulin)

Aka. TeBG (TESTOSTERONE-estrogen Binding Globulin)

SHBG binds to estrogen and TESTOSTERONE in the blood(making them less bioavailable)

–   Bioavailability of ESTRADIOLor TESTOSTERONE is determined by the level of SHBG - ESTRADIOL and TESTOSTERONE travel in the blood either strongly (but reversibly) bound to SHBG (ESTRADIOL 40%) or loosely bound to serum albumin (ESTRADIOL 59%).E.g. Only about 1-2% of circulating ESTRADIOL is “free”to enter a cell and activate its receptor.


SBGH level is delicately balanced by enhancing and inhibiting factors:

–    SHBG is ▲  increased by: (makes otherwise unbound hormones LESS bioavailable)

✔ Liver disease, alcohol

✔ Hyperthyroidism - high levels of thyroxine (T3)

✔ Anorexia

✔ High levels of estrogen - E.g. use of HRT, oral contraceptives (metabolized by liver);

✔ High levels of GROWTH HORMONE

–    SHBG is ▼ reduced by: (makes otherwise bound hormones MORE bioavailable)

✔ Higher circulating INSULIN levels (note however, that recent evidence reveals that liver's fat production reduces SHBG, and not any direct effect of INSULIN);

✔ Obesity - obesity leads to high insulin levels, which causes a reduction in the liver's productionand circulating levels of SHBG (see note above); note that obesity also increases estrogen production in adipose cells via the aromatase enzyme; Thus, obesity can promote cancers such as breast and endometrial cancer –as estrogen becomes more bioavailable (free/unbound to SHBG) for its target tissues.

✔  Hypothyroidism;

✔  Androgens;

✔  Corticosteroid-binding globulin (CBG)


✔ Cushing's disease;

✔ Soy - up to 10% reduction;

✔ Nettle root - contains compounds that bind to SHBG; nettle root is also anti-aromatase and therefore acts against estrogen production.

High/Low SHBG Conditions

–   Low SHBG (making hormones MORE bioavailable) - seen in polycystic ovary syndrome, diabetes, hypothyroidism.

–   High SHBG (making hormones LESS bioavailable) - seen in pregnancy, hyperthyroidism, anorexia nervosa. Recent research links high SHBG levels with breast and testicular cancer.

SHBG production sites

–   SHBG is produced mainly in the liver cells and released into the bloodstream - other production sites are the brain, uterus, placenta and testes (where it is sometimes called androgen-binding protein).

CBG (Corticosteroid-binding Globulin)

CBG (a.k.a. transcortin) binds to PROGESTERONE , CORTISOL (and other corticosteroids)in the blood

–   Bioavailability of PROGESTERONE , CORTISOL (and other corticosteroids) is determined by level of CBG


–   PROGESTERONE is bound by CBG (~18%), albumin (~80%), SHBG (0.6%) and ~2% exists in the free state

Clinical Reproductive medicine and surgery, 2007

CBG level is balanced by enhancing and inhibiting factors:

–    CBG is ▲  increased by: (makes otherwise unbound hormones LESS bioavailable)

✔ Estrogens / Pregnancy

–    CBG is ▼ reduced by: (makes otherwise bound hormones MORE bioavailable)

✔ Cirrhosis (chronic liver disease);

✔ Alcohol

CBG production

–   CBG is produced by the liver

side bar
DISCLAIMER: The content on this website is intended for informational, and educational purposes only and not as a substitute for the medical advice, treatment or diagnosis of a licensed health professional. The author of this website is a researcher, not a health professional, and shall in no event be held liable to any party for any direct, indirect, special, incidental, punitive or other damages arising from any use of the content of this website. Any references to health benefits of specifically named products on this site are this website author's sole opinion and are not approved or supported by their manufacturers or distributors. COPYRIGHT 2009-2019