Testosterone, Bioavailable

Alternative Names
  • Bioavailable Testosterone

Test Code: 4021

CPT: 84410
Tests Included Testosterone, SHBG, Albumin
Use In addition to SHBG, Testosterone is bound weakly to Albumin (~30% bound).  Because testosterone bound to albumin may dissociate, this fraction is also considered “bioavailable” to cells. The bioavailable fraction as it relates to albumin can therefore also be calculated and added to free testosterone for clinical consideration.
Clinical Utility An abnormally low total testosterone level in males can be indicative of hypogonadism, hypopituitarism, hyperprolactinemia, renal failure, hepatic cirrhosis, or Kleinfelter’s syndrome. Men experiencing symtopms of low T and using opioid medications for >90 can exhbit Opioid Induced Androgen Deficiency (OPIAD).  High total testosterone values in males can be caused by adrenal and testicular tumors, congenital adrenal hyperplasia or abnormalities of the hypothalamic-pituitary-testicular axis.1

Increased female total testosterone levels may indicate polycystic ovary syndrome (PCOS), stromal hyperthecosis, ovarian and adrenal tumors, congenital adrenal hyperplasia and other disorders of the hypothalamic-pituitary-ovarian axis.2
Intended Patient Population 18+ and Older Adult Males
Patient Preparation None Specified
Sample Serum, Plasma
Tube Red, Green, Tiger
Volume 4mL Whole Blood (1mL Serum/Plasma)
Min Sample Volume 0.5 mLs
Reference Ranges Testo - M 18-39 yrs old; 300-1080 ng/dL
Testo - M 40-59 yrs old; 300-890 ng/dL
Testo - M 60-150 yrs old; 300-720 ng/dL
SHBG - M ≥ 18 yrs old;  11-80 nmol/L
Free Testo (calc) M ≥ 18 yrs old;  4.7-24.4 ng/dL
Bioavailable Testo (calc) M ≥ 18 yrs old;  131-682 ng/dL
Analytical Measurement Range Testo - 6.25-1600.00 ng/dL
SHBG - 0.161-200 nmol/L
Units ng/dL
Test Methodology LC/MS/MS &
Chemiluminescent Immunoassay
Test Turnaround Time 5 Days
Limitations None Specified
Shipping Requirements Refrigerated
Specimen Stability 7 Days RT
4 Days RF
Reject Criteria 0
Laboratory Developed Test (LDT) Yes
CMS Guidance None
  1. Wilson, JD, Foster, DW (Eds) Williams Textbook of Endocrinology, 8th Edition, W.B. Saunders, Philadelphia, Pennsylvania 19106, 1992, page 822-832.
  2. Brutis, CA, Ashwood, ER (Eds) Tietz Fundamentals of Clinical Chemistry, 4th Edition W.B. Saunders, Philadelphia, Pennsylvania 19106, 1996, page 671 - 672.

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