Question 1

What is the difference between total testosterone and SHBG?

Accepted Answer

Total testosterone measures all testosterone in the blood, while SHBG measures the transport protein that binds to hormones. SHBG is required when measuring the biologically active free testosterone fraction as distinct from the 98% of total testosterone which is bound and inactive. Understanding both values helps determine how much hormone is actually available for the body to use.

Question 2

Can birth control pills affect SHBG levels?

Accepted Answer

Birth control pills or other forms of oral estrogen raise the SHBG, and a recent study found that birth control pills can raise SHBG and even after stopping them for at least a year, the SHBG remains high. This can result in lower bioavailable testosterone levels, which may affect libido and energy levels.

Question 3

How does SHBG relate to PCOS diagnosis?

Accepted Answer

A reduction in plasma SHBG is often used as an indicator of hyperandrogenism in women with PCOS. SHBG is reduced in insulin resistance and actually a very good marker for insulin resistance. Many women with PCOS have a high-normal or even a normal total testosterone but have a low SHBG because they have insulin resistance.

Question 4

Does age affect SHBG levels?

Accepted Answer

Normal SHBG levels vary according to gender and age. In men, there is an age-related gradual rise, possibly secondary to the mild age-related fall in testosterone production. This process can result in bioavailable testosterone concentrations that are much lower than would be expected based on total testosterone measurements alone.

Question 5

Can diet and lifestyle changes affect SHBG levels?

Accepted Answer

Yes, lifestyle factors can significantly impact SHBG levels. Obesity is associated with significantly lower SHBG, and the association between obesity and lowered SHBG is greater than the association of aging with increased SHBG. Weight loss, regular exercise, and dietary changes that improve insulin sensitivity can help normalize SHBG levels.

Question 6

What medical conditions can cause abnormal SHBG levels?

Accepted Answer

Many conditions can affect SHBG production. SHBG levels can be affected by decreased or increased testosterone or estrogen production, and certain diseases and conditions such as liver disease, hyperthyroidism or hypothyroidism, and obesity. Insulin resistance, metabolic syndrome, and various medications can also influence SHBG concentrations.

SHBG (Sex Hormone Binding Globulin)