A protein made by your liver, the full hormone is called Sex Hormone Binding Globulin. It binds to oestrogen, testosterone and DHT (dihydrotestosterone) removing them from direct circulation, modulating the bioactivity of sex steroids by limiting their diffusion into target tissues throughout your body, found in both men and women. This role mainly controls the amount of testosterone your tissue can use and keeping your sex-hormone processed in check. Kind of like a train, dropping hormones off at specific tissue sites and into cells directly.
Do oral contraceptives (OCP) affect SHBG? Yes indeed. Any OCP’s that contain oestrogen increases SHBG.
Does the thyroid play a role? Yep. Thyroid hormones influence SHBG by altering hepatic hormone production, so hypothyroidism decreases production and hyperthyroidism increases.
Low levels: of SHBG may relate to Obesity, Type 2 Diabetes and Hypothyroidism (low-grade inflammation that occurs in obesity and T2D may affect the pathway in SHBG production). Because it controls testosterone levels, when SHBG levels are low in women its often the reason testosterone levels increase and cause facial hair growth and acne.
High levels: Hyperthyroidism, Hepatitis and HIV Ladies – maintaining high SHBG levels is still important after menopause, it can help lower the risk of developing breast cancer. In terms of the menstrual cycle, SHBG levels peak around ovulation (oestrogen levels affect SHBG and oestrogen peaks just prior to ovulation). One study found ethnicity may impact SHBG levels, with Swedish women reportedly having higher levels than non-Swedish women! Cycle length can also impact levels. Research shows people with cycles <26 days have higher SHBG levels.
When would you want to test this? Like all blood tests (out of the thousands that there are) it depends on the patient as everyone is unique. Most commonly SHBG is measured in the evaluation of low testosterone (possible androgen deficiency) in men or when there are symptoms of excess male hormones in women, such as acne, facial hair, a deepened voice or scalp balding.
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Want to know more about hormones? Incase you’ve missed previous hormonal posts, see below.