Topical Estradiol Gel Leading to Laboratory Error in Serum Estradiol Measurement: A Diagnostic Pitfall

Estradiol gel is commonly used as an estrogen replacement therapy for patients with menopausal symptoms. Herein, we present a case of a patient with iatrogenic primary ovarian insufficiency who exhibited an abnormally elevated serum estradiol concentration (5634.0 pg/mL) during routine estradiol monitoring. A detailed interview revealed that the cause of these elevated levels was contamination of the needle used to draw her blood with gel from her skin. To the best of our knowledge, this is the first report of estradiol concentrations exceeding 2000 pg/mL due to such contamination. This phenomenon is not well known and is not described in package inserts or guidelines. There is a risk that misleadingly high serum estradiol concentrations may lead to inappropriate dose adjustments, potentially negatively affecting the health of the patients. Thus, clinicians must provide precise instructions to patients to avoid applying the gel around the area where venipuncture is to be performed.