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Panels › Hormone Panels › Testosterone

Testosterone

Significance
Testosterone is the major androgen responsible for sexual differentiation and male secondary sex characteristics. In the circulation, approximately 55% is tightly bound to sex hormone binding globulin (SHBG), 42% to albumin, and about 3% is free (unbound). The free and about half of the albumin fraction is bioactive. In males, testosterone is primarily secreted by the testes and levels exhibit diurnal variation with the highest levels between 6 and 9 AM and lowest around midnight. Testosterone levels begin to decline with age starting at about 40 yrs. In females, about half of the testosterone is derived from peripheral conversion of androstenedione. Major applications of testosterone measurement reside with assessment of sexual development, gonadal disorders, hyperandrogenic syndromes, menstrual disorders, and hormone replacement therapy.

Analysis
Determination of Cortisol is performed by enzyme immunoassay.

Patient Preparation
Morning specimen is preferred. Where possible/appropriate avoid medication that can alter testosterone levels (at least 48 hrs prior to specimen collection).

Specimen requirements
Serum specimen - from a plain redtop or a redtop gel (tiger top) tube. Separate serum from cells after centrifugation, if a plain redtop tube is used. Minimum volume required is 0.5 mL. Specimen should be kept refrigerated where possible.

Shipping Instructions
Ship specimen at ambient temperatures. For long distance shipping, ship with ice packs.

Additional information
http://www.labtestsonline.org/understanding/analytes/testosterone/test.html