Drugs That Distort Urinary Sex Steroid Metabolite Testing

A Changed Result Is Not Always a “False” Result

Two different problems are often grouped together as interference:

1. Biological modification: a medicine actually changes hormone production, binding, conversion, or excretion. The measured value may be analytically correct but cannot be interpreted as an untreated baseline.
2. Analytical interference: the assay reports the wrong value because another compound affects the measurement method.

This distinction matters. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) and immunoassays have different vulnerabilities, and one laboratory’s instructions cannot safely be copied to another method.

Hormonal Contraceptives

Combined hormonal contraceptives suppress ovarian steroid production and expose the body to synthetic estrogen and progestin. In a prospective study of 55 women, three months of ethinyl estradiol/levonorgestrel use materially changed the urinary steroid profile, with wide person-to-person variation in epitestosterone response 1. A separate controlled analysis also found that hormonal contraception and genetic variation both affected steroid-profile markers 2.

These findings do not support a universal “six- to eight-week washout.” They show that contraceptive status must be part of the interpretation. If the clinical question is how hormones look while using contraception, collecting on treatment may be appropriate. If the question is untreated ovarian function, a clinician must decide whether changing contraception is medically appropriate and how long recovery should be allowed.

Menopausal Hormone Therapy and Testosterone

Oral, transdermal, vaginal, implanted, and injected hormones do not create interchangeable profiles. Route, dose, formulation, and time since the last dose can all affect what appears in urine.

Controlled urinary profiling after testosterone administration demonstrates broad changes beyond a single testosterone value 3. A panel obtained during testosterone therapy therefore describes exposure and metabolism on therapy; it should not be presented as a baseline measure of endogenous production.

The same principle applies to estradiol and progesterone therapy. Record the exact product and route. A result obtained after oral micronized progesterone cannot be interpreted as though no progesterone had been taken.

Finasteride, Dutasteride, and Other Enzyme-Blocking Drugs

Finasteride and dutasteride inhibit 5-alpha-reductase, so changes in DHT-related metabolites are expected. A metabolomic study of men treated with finasteride found differences in urinary steroid-hormone pathways 4. That is a pharmacologic signal, not proof that the specimen is invalid.

Aromatase inhibitors alter conversion of androgens to estrogens. Glucocorticoids can also change parts of the urinary steroid profile; a repeated-dose study found treatment-dependent reductions in several androgen metabolites and ratios 5. Thyroid hormone administration has likewise been shown to alter selected urinary steroid markers 6.

Biotin: Important, but Method-Specific

High-dose biotin can cause major errors in assays that use biotin-streptavidin chemistry. Studies have documented false endocrine results in susceptible blood immunoassays, including estradiol, progesterone, testosterone, and DHEA-S platforms 7.

That evidence should not be generalized to every dried-urine or LC-MS/MS panel. Ask the laboratory:

• Is the analyte measured by LC-MS/MS, gas chromatography-mass spectrometry, or immunoassay?
• Has the specific method been tested for biotin interference?
• What pre-collection interval does the laboratory validate for the patient’s dose?

How to Prepare Without Creating a New Medical Risk

Before collection, give the ordering clinician and laboratory a complete list of:

• prescription hormones and contraceptives;
• testosterone, DHEA, pregnenolone, progesterone, and “hormone support” supplements;
• finasteride, dutasteride, aromatase inhibitors, SERMs, and antiandrogens;
• oral, injected, inhaled, or topical glucocorticoids;
• thyroid hormone;
• high-dose biotin;
• dose, route, schedule, and time of the last dose;
• menstrual status, cycle day, pregnancy status, and recent hormone changes.

Do not omit a medicine from the requisition because it seems unrelated. Do not stop contraception, glucocorticoids, thyroid hormone, cancer therapy, or prescribed hormone therapy solely because an internet page recommends a washout.

When Repeat Testing Is Reasonable

A repeat may help when the medication list was missing, collection timing was wrong, the specimen was incomplete, or the result conflicts with clinical findings. If analytical interference is suspected, repeating with a different validated method may be more useful than repeating the same assay under the same conditions.