Testosterone, Total, Bioavailable, and Free, Serum

Casandra

Casandra Test Code MC93419Version 1 (DRAFT)

Performing Lab

Lab Mayo Clinic LabLab Test ID TTFBCPT Codes 84402, 84403, 84410

Testosterone, Total, Bioavailable, and Free, Serum

Clinical Use

Use

This test serves as a second- or third-order test for evaluating testosterone status, particularly when abnormalities of sex hormone-binding globulin (SHBG) are present. Testosterone is the major androgenic hormone responsible for the development of male external genitalia and secondary sexual characteristics. It also acts as an estrogen precursor in females, exerts anabolic effects, and influences behavior in both sexes. The test measures total, free, and bioavailable testosterone, which can provide a fuller picture of testosterone levels, especially when SHBG abnormalities are present.

Special Instructions

Patient's age and sex are required for this test. It is not orderable currently due to concerns around acceptable turnaround times, but an alternative test FFBTT is recommended. The preferred test for mild abnormalities of testosterone homeostasis is TTBS / Testosterone, Total and Bioavailable, Serum.

Limitations

Testosterone levels can fluctuate substantially between different days and even more rapidly. Assessment should not rely on a single measurement. Early morning levels in young males are 50% higher than p.m. levels. Oral contraceptives can reduce testosterone levels and increase SHBG, affecting the measurements of free and bioavailable testosterone. Bioavailable testosterone is often superior to free testosterone in many diagnostic situations, but levels can be influenced by changes in SHBG levels due to conditions or treatments such as corticosteroids and sex steroids.

Test Details

New York Approved