Contents

Search

free testosterone

Specimen: 1) serum (red top); separate serum; store frozen 2) plasma (green top) {heparin}; separate plasma; store frozen Reference interval: 1) adult male: 9-30 ng/dL 2) females: 0.3-1.9 ng/dL Indications: 1) evaluation of testosterone concentrations in clinical states in which sex hormone-binding globulin (SHBG) may be altered - decreased serum SHBG - *obesity, diabetes mellitus, nephrotic syndrome, hypothyroidism, acromegaly, & in patients taking steroids or progestins [] - increased serum SHBG - *older age, HIV1 infection, cirrhosis & hepatitis, hyperthyroidism, hyperestrogenic states (pregnancy oral contraceptives) & in patients taking certain anticonvulsants 12] 2) adolescent polycystic ovary syndrome [2] - *measurement of free testosterone before & after dexamethasone administration may use useful 3) *relatively few conditions in which free testosterone is necessary (total testosterone is generally sufficient) a) levels < 150 ng/dL or > 350 ng/dL identify or exclude biochemical hypogonadism reasonably accurately b) when levels fall between these thresholds, consider serum free testosterone [3] Principle: - free testosterone is probably the physiologically active form of testosterone - only 1-3% of circulating testosterone is in the free form; most is bound to SHBG - there is also non-specific binding to albumin - albumin-bound testosterone may be physiologically active - bioavailable testosterone measures free plus albumin-bound testosterone Decreases: males 1) hypogonadism 2) orchidectomy 3) estrogen therapy 4) Klinefelter's syndrome 5) hypopituitarism 6) testicular feminization 7) hepatic cirrhosis 8) andropause* 9) levels drop in men with children * 40% of men > 45 years of age [4] Increases: females: - polycystic ovary syndrome (female) Notes: - female athletes with higher free testosterone tended to perform better in competitive events [11]

Related

bioavailable testosterone testosterone (Delatestryl Testopel, Striant, Intrinsa, Xyosted) testosterone in serum

Specific

testosterone.free+weakly bound in serum/plasma

General

special chemistry test

References

  1. ABC's of Interptretive Laboratory Data, 4th ed, Bakerman S et al (eds), Interpretive Laboratory Data Inc, Scottsdale, AZ, 2003 http://www.bakermanbooks.com
  2. Moll GW et al, J Pediatrics 102:461, 1983
  3. Anawalt BD et al. Performance of total testosterone measurement to predict free testosterone for the biochemical evaluation of male hypogonadism. J Urol 2012 Apr; 187:1369. PMID: 22341266
  4. Panel of 5 tests Laboratory Test Directory ARUP: 70102
  5. Panel of 4 tests Laboratory Test Directory ARUP: 70109
  6. Panel of 3 tests Laboratory Test Directory ARUP: 70111
  7. Panel of 3 tests Laboratory Test Directory ARUP: 81056
  8. Panel of 3 tests Laboratory Test Directory ARUP: 81057
  9. Mini Panel of 2 tests: Sex Hormone Binding Globulin 1 . Testosterone, Free LC-MS/MS Laboratory Test Directory ARUP: 81059
  10. Panel of 5 tests Laboratory Test Directory ARUP: 2001763
  11. Monaco K Androgens Linked to Competitive Edge in Female Athletes - Higher free testosterone levels tied to better performance in stamina, visuospatial events MedPage Today. July 03, 2017 https://www.medpagetoday.com/Endocrinology/Steroids/66402
  12. Sargis RM, Davis AM Evaluation and Treatment of Male Hypogonadism. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. JAMA. Published online March 17, 2018. PMID: 29550857 https://jamanetwork.com/journals/jama/fullarticle/2675569