STATS ARTICLES 2010
Is your teenage son going to get man boobs?
Rebecca Goldin Ph.D, January 6, 2010
Plasma Phthalate Levels in Pubertal Gynecomastia
A few weeks ago, a study by Turkish researchers in the journal Pediatrics reported an association between exposure to the plasticizer DEHP and gynecomastia (man boobs) in pubescent boys. Given that claims about the potential risk from exposure to phthalates (the family name for such chemicals as DEHP) has generated enormous public concern, often through exaggeration or misconstrual of the actual research findings, STATS took a look at the strengths and weaknesses of the research.
Overall, this study has some good evidence that DEHP is correlated with gynecomastia in pubescent boys, but due to the nature of the study, cause and effect are impossible to tease out, so there are important caveats.
All of the results that are relevant are statistically significant. The authors took care that their samples were not contaminated. The results seem to be independent of other factors such as testicular size or body mass index (BMI) -- though they did not have the statistical strength to evaluate the association in each BMI category. The hormone levels of kids suffering from gynecomastia were also normal. Certainly, the study raises some important questions and suggests that a larger-scale study should be undertaken. While gynecomastia, typically, is not by itself problematic (if anything, the condition occurs as a symptom of other possible problems, though it's so common as to even call that claim into question), it is still indicative of a possible imbalance in how hormones are processed, which could be attributed to DEHP, though cause is certainly not established here.
Very few other aspects of lifestyle or possible exposure were considered by the researchers, and it is entirely possible (if not likely) that phthalate exposure correlates with other activities that could be part of the cause behind gynecomastia. The study would be stronger if it controlled for alcohol intake (implicated in some cases), drug use (especially hormonal drugs, but also marijuana), and antibiotics. Also, in terms of weight: there are only two controls in the lowest BMI group, and that is a bit unsettling (though the overall sample size is big enough).
It is important to keep in mind that a huge proportion of young men get gynecomastia -- though very few at a painful level. In almost all cases, it resolves on its own. One thing that would make this a stronger study (in addition to controlling for other suspected causes of gynecomastia) would be to see if those who have it are also more likely to stay that way (i.e. for their situation not to resolve itself) if they have higher levels of DEHP/MEHP.
There is one further problem with the study: it makes the claim that research by Shanna Swan's has shown that DEHP has reproductive developmental effects for babies similar to those found in animals. But Swan was unable to show these effects for DEHP or for its metabolites. She showed a correlation for different phthalates (maybe even a grouped phthalate score) but not for DEHP.