Environmental Gynecomastia

Abstract

In this issue of Endocrine Practice, Drs. Martinez and Lewi describe a 60-year-old man who developed gynecomastia associated with high serum estradiol and estrone levels. After an extensive evaluation, they concluded that the etiology was an enormous intake of soy milk—3 quarts per day—which was estimated to provide 361 mg of phytoestrogens, composed primarily of the isoflavones genistein and daidzein. After discontinuing the soy milk, the estrogen levels gradually returned to normal and the patient’s mastodynia resolved ( 1. Martinez J. Lewi J.E. An unusual case of gynecomastia associated with soy product consumption. Endocr Pract. 2008; 14: 415-418 Abstract Full Text Full Text PDF PubMed Scopus (43) Google Scholar ). Although it is possible that the gynecomastia was the result of the massive phytoestrogen ingestion, phytoestrogen intake cannot explain the elevated estradiol and estrone levels for 3 reasons. First, the authors state that the estrogens were measured by liquid chromatography/tandem mass spectrometry. This methodology is highly specific, and the phytoestrogens should not be measured as either estradiol or estrone. Second, estrogens have a short half-life, and once an exogenous source is removed, the serum levels decrease rapidly, which was not the case with the patient described. Finally, several studies in women have shown that soy phytoestrogens actually decrease endogenous estrogen production ( 2. Xu X. Duncan A.M. Merz B.E. Kurzer M.S. Effects of soy isoflavones on estrogen and phytoestrogen metabolism in premenopausal women. Cancer Epidemiol Biomarkers Prev. 1998; 7: 1101-1108 PubMed Google Scholar , 3. Lu L.J. Anderson K.E. Grady J.J. Kohen F. Nagamani M. Decreased ovarian hormones during a soya diet: implications for breast cancer prevention. Cancer Res. 2000; 60: 4112-4121 PubMed Google Scholar ). Thus, the source of the elevated estrogens in this patient remains unclear, but is likely to be exogenous based upon the very high levels. Had this represented endogenous production, he would likely have had a feminizing testicular or adrenal tumor, which the authors ruled out with imaging studies, and which would not have spontaneously resolved leading to a return of the estrogen levels to within the normal male range. This patient may indeed represent an example of environmental gynecomastia, but not necessarily due to the phytoestrogens.