Hypothermia in iron deficiency due to altered triiodothyronine metabolism

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Abstract
Fe-deficient rats due to dietary deficiency become hypothermic and have excessive catecholamine response when exposed to an ambient temperature of 4.degree. C. This is not due to changes in body insulation, since hair thickness is unaltered. Differences persist after hair removal. Cutaneous vasoconstriction is intact. O2 consumption of Fe-deficient animals at 4.degree. C is reduced, 39 .+-. 3 ml .cntdot. Kg-1 .cntdot. min-1 compared to 63 .+-. 2 in control animals. Thyroxine (T4) values at 4.degree. C were 4.34 .+-. 0.20 .mu.g/dl sera compared to control values of 3.6 .+-. 0.32. Triiodothyronine (T3) values of Fe-deficient animals in the cold were 48 .+-. 6.8 ng/dl compared to 72 .+-. 5.6 in control animals. Treatment of Fe-deficient animals with Fe normalized plasma T3 response at 4.degree. C within 6 days. Thyroidectomized Fe-deficient animals injected with T3 did not show hypothermia at 4.degree.C thyroidectomized Fe deficient animals injected with T4 showed hypothermia, increased catecholamines and decreased T3 levels compared to non-deficient animals similarly treated. Fe deficiency impaired conversion of T4 to T3 and this was responsible for hypothermia observed.