Sex hormone binding globulin, also known as SHBG, binds to sex hormones like testosterone and estradiol. This limits the amount of free hormone available in your body to exert its effects.
Low levels of SHBG can be associated with conditions like hyperthyroidism, pituitary disease, and hypogonadism. InsideTracker includes the SHBG test in its at-home Hormone and Fertility test kit.
Testosterone
Testosterone, produced by Leydig cells in the testes in men and by the ovaries in women, is the predominant sex hormone. It has both androgenic and anabolic properties, and it promotes secondary male characteristics as well as muscle growth (by increasing protein synthesis). A large proportion of circulating testosterone is bound to SHBG and albumin, and the unbound fraction is known as free testosterone. Unbound testosterone is more biologically active and readily available to the tissues of the body.
SHBG is a glycoprotein made mostly in the liver. It binds to any of 17 sex hormones in the bloodstream, including both testosterone and estrogen. When hormones are bound to SHBG, they can’t enter tissues and have an effect. The unbound hormones can enter tissues, but only if they are free from SHBG. SHBG acts almost like a buffer, controlling the amount of active hormones that are released into the bloodstream.
The levels of SHBG in the bloodstream drop as you age. This is due to a combination of causes. In men, some of the causes include a decrease in the number and size of the testicles (as the Leydig cells shrink with age), low testosterone production as the ovaries shrink, and a loss of libido. Other factors that contribute to low SHBG in men are hypogonadism, Addison’s disease, and pituitary problems.
In addition, the low levels of SHBG in the body are linked to the development of diabetes. In one study, women with lower levels of SHBG had a higher risk of developing type 2 diabetes than women who had higher levels. (6)
To increase the levels of SHBG in the bloodstream, you can take supplements that contain plant-based proteins. Vegetable-based protein supplements can also help to improve the absorption of other nutrients from the digestive tract. A diet high in protein can also increase SHBG without lowering total testosterone, though it is important to focus on eating a healthy and balanced diet. Depending on the cause of your low SHBG, you may need to work with your doctor to find out how to treat it. Testosterone Replacement Therapy can be used to treat the condition, but it’s important to discover what is causing your low SHBG levels and develop an appropriate treatment plan.
Estrogen
Estrogen is a powerful hormone that helps regulate the menstrual cycle in females and powers the development of secondary sex characteristics (breast development, pubic hair growth) starting at puberty. Estrogen is made by the ovaries, the adrenal glands, and adipose tissue, and it also travels throughout the body and binds to estrogen receptors in the tissues and organs that need them. Estrogen can cause acne, increase uterine cancer risk, decrease sexual desire, and can lead to weight gain in women and men, especially around the abdomen. High levels of estrogen can also increase your risk for breast and ovarian cancer, depression, and osteoporosis.
Estradiol is the most common type of estrogen and it’s the form of estrogen your body uses during pregnancy and childbirth. After birth, the body converts any excess estradiol to other forms of estrogen that are no longer active. Estrogens have the ability to lower serum cholesterol and triglyceride concentrations, which can help protect against atherosclerosis before menopause. Estrogens can also increase the level of binding proteins that transport cortisol and thyroxine in the bloodstream.
SHBG is a protein that’s made in the liver and helps bind and transport sex hormones throughout your body. It has a special affinity for three sex hormones, including dihydrotestosterone and testosterone, as well as estrogens like estrone and estradiol. SHBG regulates the proportion of sex hormones that are available to be used in the body.
Low SHBG levels may indicate a variety of hormone disorders, such as polycystic ovary syndrome, menopause, and androgen deficiency. High SHBG levels may indicate the presence of certain types of tumors, such as fibroid tumors and endometrial carcinoma.
Talk to your doctor if you have abnormally low or high SHBG levels to determine the best treatment options for you. If you have a condition that causes low SHBG, your doctor may prescribe medication to increase its levels. Your doctor will recommend the best dose and delivery method for your specific situation, such as an oral tablet, transdermal patch, gel or emulsion, slow-releasing suppository, or vaginal cream or ring.
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