A time-course study of hypothyroidism-induced hypotension: its relation to food deprivation.

Concentrations of 0.05, 0.01 and 0.2% propylthiouracil (PTU), incorporated into standard rat chow, induced hypothyroidism in male Sprague-Dawley rats following 6-8 weeks administration. The concentrations caused a progressive decrease in arterial blood pressure (BP), heart rate (HR), body weight (BW), food intake (FI), levels of triiodothyronine (T3), thyroxine (T4) and an increase in thyrotropin (TSH) levels. There was no clear-cut dose-dependent change in these parameters, since the values obtained for the 3 groups were not significantly different from one another, but were significantly lower than that of control rats (euthyroid). Pair-feeding studies between partial food-deprived euthyroid rats and PTU-induced hypothyroid rats showed that both types of treatment caused a decrease in BW, BP, HR, colonic temperature, levels of T3, T4 and an increase in TSH. The changes were significantly (P less than .05) greater in the hypothyroid than in the food deprived rats at the end of the 6th week and thereafter.