Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1218 page)

SEX HORMONE–BINDING GLOBULIN (SHBG)

   Definition

   A glycoprotein, synthesized in the liver, which binds testosterone and 5-dihydrotestosterone with high affinity, and estradiol with a somewhat lower affinity. SHBG typically circulates at higher concentrations in women than in men, due to the higher ratio of estrogens to androgens in women. Administration of androgens tends to be associated with decreased SHBG levels. Because variations in the carrier protein levels may affect the concentration of testosterone in circulation, SHBG levels are commonly measured as a supplement to total testosterone determinations. The “free androgen index” (FAI), calculated as the ratio of total testosterone to SHBG, has proved to be a useful indicator of abnormal androgen status in conditions such as hirsutism.

   
Normal range:
see Table 16.74.

TABLE 16–74. Normal Ranges of Sex Hormone–Binding Globulin

   Use

   Diagnosis and follow-up of women with symptoms or signs of androgen excess (e.g., polycystic ovarian syndrome and idiopathic hirsutism)

   As an adjunct in monitoring sex steroid and antiandrogen therapy

   As an adjunct in the diagnosis of disorders of puberty

   As an adjunct in the diagnosis and follow-up of anorexia nervosa

   Interpretation

Increased In

   Hyperthyroidism

   Hepatic cirrhosis

   Pregnancy