TESTOSTERONE - serum

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Specimen: 5 mL blood in plain tube.

Method: Immunoassay. The laboratory may estimate one or more of the following: free testosterone, total testosterone, sex hormone binding globulin (SHBG), free androgen index (from total testosterone and SHBG), dihydrotestosterone.

Reference Interval: Levels are method and age dependent. See Table 7 .

Application: Assessment of hirsutism or virilisation in females; investigation of testicular failure or precocious puberty in males.

Interpretation: Increased levels may be found in women with hirsutism or virilisation and in (phenotypic) women with total androgen insensitivity. Levels are increased in males with precocious puberty. Decreased levels are found in males with testicular failure, either primary or secondary to hypopituitarism. In plasma, testosterone is bound to SHBG, so abnormal levels of SHBG may cause a discrepancy between free and total testosterone.

Reference: Wheeler MJ. Ann Clin Biochem 1995; 32: 345-357.

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