Effect of thyroxine supplementation on the response to perfluoro-n-decanoic acid (PFDA) in rats.

The effects of thyroxine (T4) supplementation on perfluoro-n-decanoic acid- (PFDA) induced decreases in food consumption, body weight, and body temperature were examined. A dose-response study was carried out with 50-, 100-, 200-, or 250-micrograms/kg ip doses of T4 for 7 d prior to PFDA administration, and daily dosing with T4 was continued for an additional 30 d. From this study a T4 dose of 200 micrograms/kg was chosen, and subsequent experiments were conducted with this dose. Supplementation with T4 at 200 micrograms/kg daily alleviated the hypophagia but not the severe weight loss and hypothermia produced by PFDA treatment. Our results suggest that some component of the thyroid axis plays a role in feeding behavior. In addition, the PFDA-induced wasting syndrome and hypothermia appear to be unrelated to changes in serum thyroid hormones. The unexpected observation that severe weight loss occurred in the presence of essentially normal food intake suggests that PFDA alters basic cellular metabolic processes.