Clinical epidemiology studies on potential effects of endocrine disrupting chemicals (EDCs) should exclude subjects with obesity as determined by BMI

Obesity as determined by BMI is a confounder in clinical evaluations of the effects of endocrine disrupting chemicals (EDCs). Validated regulatory tests are used to determine whether a chemical acts via a mode of action (MOA) that affects estrogen, androgen, thyroid or steroidogenic pathways. Test batteries for evaluating EDCs include QSAR, in vitro assays, and animal testing. Studies suggest that EDCs pose the greatest risk during prenatal and early infant development when organ systems are developing. Health effects include lowered fertility, endometriosis, and cancers associated with estrogenic activity. Epidemiology studies on adverse effects of EDCs in the general population are difficult to conduct due to very low exposures of EDCs in non-occupational cohorts, and lack of exposure measurements between cases and controls. In contrast with very low levels of hormonal perturbation from nano-molar to micro-molar exposures to EDCs, adipose tissue in obesity alters estrogen, testosterone, thyroid stimulating hormone, and inflammation levels. Obesity in pregnancy and gestational diabetes are associated with adverse outcomes in infants and children including autism, poor motor skills, lowered IQ, and altered birth weight. Neonatal effects of obesity are confounded by average lower socio-economic status. The already perturbed endocrine balance in overweight or obese persons renders them particularly worthy subjects for clinical epidemiology investigations on the possible effects of endocrine disrupting chemicals. However, inclusion of subjects with obesity requires accounting for potentially confounding effects of the hormonal influences arising from excess adiposity. If subjects with obesity are to be included in clinical epidemiological evaluations related to hormonal effects, the subjects should be classified by body fat percentage rather than by the much less exact measure of body mass index (BMI).