Laboratory testing for testosterone (T) levels should be standardized and a hypogonadism diagnosis should be made using both a blood test and a physical exam, a panel of experts says.
The experts’ review, led by the American Urological Association, found a number of issues that need to be considered when measuring testosterone.
First, testosterone itself can be variable. For example, men’s testosterone levels can fluctuate based on the time of day, glucose intake, medications taken, and triglyceride levels. A man’s levels on one day might be much different the next.
Second, laboratory procedures could affect testosterone measurements. The authors noted that the types of collection tubes used, the ways samples are stored, and the time that elapses between blood draw and analysis can all affect the final numbers.
“In some cases, testosterone (T) levels, tested on the same day from a blood sample taken from a single patient, differed by as much as 30 percent from one lab to the next,” lead author Dr. Darius A. Paduch of NewYork-Presbyterian/Weill Cornell Medical Center said in a press release.
Third, there is no consensus among professionals on the definition of testosterone deficiency and what the cutoff point should be. A measurement of 300 ng/dL is a commonly accepted cutoff, but what is low for one man might not necessarily be low for another.
The authors explained, “…this panel emphasizes that signs and symptoms suggestive of hypogonadism and laboratory measured T level are equally important indicators of hypogonadism and indicators for treatment until more research is done. We believe that rigid use of T cutoff (300 ng/dL) may lead to unnecessary treatment of asymptomatic men and undertreatment of men with persistent signs and symptoms.”
They added that many studies on the subject have involved men over age 65, but patients do not always fall into this demographic category. Studies of younger men of reproductive age would be helpful in determining “normal” testosterone ranges, they said.
The panel made several suggestions for future research and improvement, including the following:
• Clinical laboratories should enroll in accuracy-based programs, such as the CDC Hormone Standardization Program. Using such a program could improve the portability of one patient’s results from lab to lab.
• Scientists should establish normal testosterone ranges for healthy individuals of different age groups.
• Scientists and assay manufacturers should follow similar standards of reporting.
• Studies should use validated assessment tools to evaluate sexual function and fertility. They should also use “well-defined, described, and representative populations.”
The review article will be published next month in Urology.
“ ‘Low T’ Diagnosis Needs More Than a Blood Test, Experts Say”
(March 10, 2014)
Paduch, Darius A., et al.
“The Laboratory Diagnosis of Testosterone Deficiency”
(Full-text article in press. Published online: February 17, 2014)
Weill Cornell Medical College
“Study Calls for Standardization in Measuring Testosterone Levels”
(Press release. March 6, 2014)