SHBG

SHBG sits at the intersection of liver health, insulin signaling, and sex hormone bioavailability. Production rises with thyroid hormone excess, estrogen exposure, low-calorie or low-carbohydrate diets, advanced age, and aggressive caloric restriction. Production falls with insulin resistance, obesity, non-alcoholic fatty liver disease, hypothyroidism, growth hormone excess, and high-protein high-fat hypercaloric intake. A low SHBG (under 20 nmol/L in a non-obese adult man) is a useful proxy biomarker for hepatic insulin resistance, often appearing before fasting insulin or HbA1c becomes overtly abnormal. Mendelian randomization studies suggest SHBG itself may not be causally protective; rather, it tracks the upstream metabolic state. Treating the underlying insulin resistance, through weight loss, training, and dietary changes, raises SHBG back into the healthy range over weeks to months. A high SHBG (above 60 to 70 nmol/L in men) is often seen in chronic underfueling, hypogonadal hyperthyroidism, advanced age, and certain liver diseases including viral hepatitis. The clinical consequence is reduced free testosterone for any given total T value, which can produce androgen-deficiency symptoms in men whose total testosterone reads "normal" on paper.