Triiodothyronine (T3) and thyroxine (T4) levels in iron-deficient,hypertriglyceridemic rats

Two experiments were conducted to examine the role and status of thyroid hormone in iron-deficient hypertriglyceridemic rats. In Experiment I, male weanling rats were fed 6 diets containing 2 levels of dietary iron [6 ppm(?Fe) and 240 ppm(+Fe)] and 3 combinations of fats [14% beef tallow +1% safflower oil(B), 7.5% beef tallow +7.5% safflower oil(BS) and 15% safflower(S)]. After 3 weeks, rats receiving ?Fe diets had elevated triglyceride (TG) and depressed triiodothyronine(T3) and thyroxine (T4) levels in serum, regardless of the fat source. No difference in the post-heparin lipolytic activity could be detected after 6 weeks of dietary treatment between rats fed +Fe and ?Fe diets. Feeding the BS+Fe diet to the BS?Fe rats for 1 week brought their serum TG, T3, and T4 to levels similar to those of rats fed the BS+Fe diet for 7 weeks. In Experiment II, male weanling rats were fed B diets containing 6 levels of dietary iron (3, 6, 10, 15, 30, and 60 ppm) for 4 weeks. Weekly determinations of packed cell volume(PCV), serum T3, T4, and TG were made. PCV, serum T3 and T4 levels increased as dietary iron content increased. The relationship between serum TG level with dietary iron level or PCV was quadratic, curvilinear. Data also suggest that part of the iron effect on serum TG level is thyroid hormone related.