Table 2: Factors associated with increased (falsely elevated total testosterone) and decreased (falsely decreased total testosterone) sex hormone binding globulin levels.

Increased serum SHBG concentration	Decreased serum SHBG concentration
Use of certain drugs (oestrogen, tamoxifen, phenytoin, barbiturates) Hyperthyroidism HIV Ageing Hepatocellular dysfunction (acute hepatitis, cirrhosis)	Use of certain drugs (androgens, progesterone, TNF-α inhibitors) Metabolic syndrome: obesity, non-alcoholic fatty liver disease Endocrine dysfunction (hypercortisolism, hypothyroidism, hyperprolactinaemia, acromegaly, type 2 diabetes mellitus) Pregnancy

Measurement free testosterone concentration is helpful for ruling in/out hypogonadism in these clinical scenarios. HIV = human immunodeficiency virus; SHBG = sex hormone binding globulin; TNF = tumour necrosis factor.