### What is Sex Hormone Binding Globulin (SHBG)? Sex hormone binding globulin (SHBG) is a protein found in your blood that binds to certain hormones. It is mainly produced in the liver and, to a lesser extent, in the testes. SHBG is an ancient protein present in all mammals, and even in some fish. ### What Does SHBG Do? The primary role of SHBG is to regulate the amount of certain hormones in your blood and determine which tissues these hormones can access. It binds to three main hormones found in both males and females: testosterone, estrogen, and dihydrotestosterone (DHT). ### Why is SHBG Important? SHBG helps transport active forms of these hormones throughout your body, ensuring they reach the tissues where they are needed. ### SHBG Blood Test A sex hormone binding globulin test measures the levels of SHBG in your blood. This test is often done alongside tests that measure testosterone levels. The blood test is simple and quick, usually taking less than five minutes. ### When is the Test Ordered? Doctors typically order this test when they suspect abnormal testosterone levels. For men, this could mean low testosterone levels, while for women, it could indicate high levels. ### Factors Affecting SHBG Levels SHBG levels can vary from person to person and change throughout your life. Factors that can affect your SHBG levels include age, sex, and various medical conditions. ### Conditions Indicated by Abnormal SHBG Levels Low SHBG levels could indicate conditions such as hypothyroidism, obesity, or type 2 diabetes. High SHBG levels could indicate hyperthyroidism, liver disease, or certain types of cancer. ### Importance of SHBG to Testosterone Ratio Sometimes, doctors compare SHBG levels to total testosterone levels to estimate how much testosterone is currently active in your body. Abnormal ratios could indicate specific health conditions. ### Next Steps If your SHBG levels are abnormal, your doctor will likely order additional tests to determine the underlying cause and create a personalized treatment plan for you.