Some athletes seek to gain a competitive advantage by taking anabolic steroids to increase muscle mass. The International Olympic Committee recommended monitoring the ratio of urinary testosterone to epitestosterone to detect anabolic steroid abuse.


Epitestosterone is 17-alpha-hydroxy-4-androsten-3-one (isotestosterone, cis-testosterone). It is the 17-alpha epimer of testosterone and is normally in the urine at about the same concentration as testosterone. With extrinsic administration of testosterone the concentration of epitestosterone decreases.


The molecular weight for both testosterone and epitestosterone is 288.4 g (source: Sigma Catalogue). The conversion factor from ng/dL to nmol/L is 0.0347.


ratio of urinary testosterone –to- epitestosterone =

= (urinary testosterone in nmol/L) / (urinary epitestosterone in nmol/L)




< 6



>= 6 and <=10



> 10


suspicious for anabolic steroid abuse



• Rare persons may have an elevated ratio without taking anabolic steroids.

• A cheat can take epitestosterone in addition to testosterone to maintain the appropriate ratio.



(1) A person with an above normal value should not be judged based on a single value.

(2) Collecting urine specimens on short notice may be helpful in reducing anabolic steroid use.

(3) The pattern of values over time may be helpful to identify abuse, especially when random testing is employed.

(4) An endocrinologic evaluation may be required to identify the patient with physiologic increase in urinary epitestosterone.

(5) Special tests may be required to identify the person taking epitestosterone to mask the anabolic steroid use (see below).


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