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

Dietary administration of propylthiouracil (0.2%) to male Sprague-Dawley rats for a period of 8 weeks induced hypothyroidism and hypotension in these animals. Resting heart rate, body weight, colonic temperature and serum thyroxine (T4) were significantly lower in the treated hypothyroid rats than in the controls. Time-course study indicates that the maximal depression of these parameters occurred about the eighth week of PTU treatment; except T4 level which declined abruptly about the second week and remained steady thereafter. The mechanism(s) of hypotension is (are) unknown but there seems to be an interrelationship between hypothyroidism-induced hypotension and the parameters monitored, since discontinuation of PTU treatment reversed that trend of the response toward control levels.