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Developmental exposure to endocrine disrupting drugs and environmental toxicants has been shown to alter a variety of physiological processes in mature offspring. Body (core) temperature (T-c) is a tightly regulated homeostatic system but is susceptible to disruptors of the hypothalamic pituitary thyroid (HPT) axis. We hypothesized that thermoregulation would be disrupted in adult offspring exposed perinatally to an HPT disruptor. Propylythiouracil (PTU) was used as a prototypical compound because of its well known antithyroidal properties. FLU was added to the drinking water of pregnant rats in concentrations of 0, 1, 2, 3, and 10 ppm from gestational day (GD) 6 through postnatal day (PND) 21. Adult male offspring were implanted with radiotransmitters to monitor T-c and motor activity (MA) and were observed undisturbed at an ambient temperature of 22 degrees C for 12 consecutive days. Data were averaged into a single 24 hour period to minimize impact of ultradian changes in T-c and MA. All treatment groups showed a distinct circadian temperature rhythm. Rats exposed to 10 ppm FLU exhibited a marked deviation in their regulated T-c with a reduction of approximately 0.4 degrees C below that of controls throughout the daytime period and a smaller reduction at night. Rats exposed to 1 or 2 ppm also had smaller but significant reductions in T-c. MA was unaffected by PTU. Overall, developmental exposure to moderate doses of an antithyroidal drug led to an apparent permanent reduction in T-c of adult offspring that was independent of changes in MA Published by Elsevier Inc.