An Unusual Case of Gynecomastia Associated With Soy Product Consumption

Jorge Martinez, MD; Jack E. Lewi, MD, FACP, FACE


Endocr Pract. 2008;14(4):415-418. 

In This Article

Case Report

A 60-year-old man was referred to the endocrinology clinic for evaluation of bilateral gynecomastia of 6 months' duration. He had noted decreased libido and erectile dysfunction during the previous 6 months, which were new symptoms. He had no change in shaving habits and no change in the size of his testes. He had gained a few pounds over the 6-month period, but he reported that weight gain was not unusual for him during the cooler months of the year, and his body mass index remained around 21kg/m2. He noted tenderness around both of his nipples, but no breast discharge. He had no history of testicular trauma, testicular inflammation, or sexually transmitted disease. He had no headaches, no visual field changes, and no change in muscle mass or strength. He reported being the biological father of a 34-year-old son.

On physical examination, he had normal genitalia and bilateral, tender gynecomastia. He was noted to have normal concentrations of β-human chorionic gonadotropin, prolactin, luteinizing hormone, follicle-stimulating hormone, and total and free testosterone. Thyroid function test results, renal function, and liver function were normal. However, his estradiol concentration was 180pg/mL (reference range, 13-59pg/mL) and his estrone concentration was 543pg/mL (reference range, 15-65pg/mL), with a normal androstenedione concentration and slightly low dehydroepiandrosterone concentration. The estradiol and testosterone levels were calculated values by liquid chromatography/tandem mass spectrometry. His sex hormone–binding globulin concentrations are listed in Table 1 . He had normal findings from ultrasonography of the testes; computed tomography of the chest, abdomen, and pelvis; and positron emission tomography. Repeated laboratory testing revealed normal concentrations of free and total testosterone and elevated concentrations of estradiol, estrone, and free estradiol. When discussing dietary history, the patient revealed he was drinking 3 quarts of soy milk per day because of lactose intolerance. He was asked to abstain from ingesting soy milk and other soy products. His estradiol and estrone concentrations began falling to near normal levels over the next several months, but then started climbing again. Upon further interviews, the patient described substituting another nonlactose product for the soy milk and did not read that it contained soy as a major ingredient. After discontinuing the nonlactose soy product, his estradiol and estrone levels decreased to the reference range and have remained normal ( Table 1 and Figure 1).

Relationship between estrogen concentrations and soy product consumption in the study patient over a period of 3 years.


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