SHBG is a liver-made carrier protein that binds testosterone and estradiol in the blood and controls how much of them circulates free enough to act on tissue. It is measured to interpret total sex hormone levels rather than as a target in its own right. As a hepatic protein, it also reflects liver and metabolic status.
No readings for this marker yet.
Raised SHBG most often accompanies high estrogen states, thyroid overactivity, liver disease, low body weight or restricted eating; it lowers the free fraction, so total testosterone can look adequate while symptoms persist. Lowered SHBG is most often seen with obesity, insulin resistance, thyroid underactivity and androgen or glucocorticoid exposure. Either direction shifts the interpretation of a total testosterone result more than it stands alone. One out-of-range value is a reason to repeat the test and discuss it with a doctor, not a conclusion.
Concentration drifts with weight, alcohol intake, thyroid state and oral estrogen, and it is stable enough across the day that fasting matters little. In women it moves with the menstrual cycle and rises markedly in pregnancy. It is read alongside total testosterone and estradiol, and with LH and FSH when the question is where along the axis a low free androgen level arises.
Reference ranges are general adult values and depend on lab, assay, age and sex. For orientation, not diagnosis — discuss results with your doctor.