Polychlorinated biphenyls and thyroid status in humans: A review

Animal studies show that exposure to polychlorinated biphenyls (PCBs) or other persistent organochlorine compounds can disrupt thyroid hormone homeostasis. In some reports dietary exposures to PCBs have also been claimed to affect circulating levels of thyroid hormones and thyrotropin (TSH) in humans. The aim of the present study was to review available epidemiologic studies within this field. A total of 13 studies fulfilled the inclusion criteria for the review. The overall impression is a lack of consistency between studies of reported correlations, neither are there any obvious interstudy dose-response associations. Thus, it cannot presently be concluded that PCB exposure has been convincingly shown to affect thyroid hormone homeostasis in humans. On the other hand, available data do not exclude such associations. It is important to be aware of the intrinsic limitations of the cross-sectional epidemiologic studies used.