Impaired thermoregulation and thyroid function in iron-deficiency anemia

Abstract

Ten women with iron-deficiency anemia, 8 with depleted iron stores (nonanemic), and 12 control women, all of similar body fatness, were exposed to a 28 °C water bath to test the hypothesis that iron-deficiency anemia impairs thermoregulatory performance. The anemic women had lower rectal temperatures than did control women (36.0 ± 0.2 vs 36.2 ± 0.1 °C, respectively, P = 0.001) and a lower rate of oxygen consumption (5.28 ± 0.26 vs 5.99 ± 0.29 mL·min-1.kg body wt-1, respectively, P = 0.04) at 100 min of cold exposure. Plasma thyroxine and triiodothyronine concentrations were significantly (P < 0.002) lower in anemic than in control women at baseline and during cold exposure. Responses of iron-depleted subjects were similar to those of control subjects. Iron supplementation corrected the anemia, significantly (P = 0.03) improved rectal temperature at 100 min, and partially normalized plasma thyroid hormone concentrations. Plasma catecholamines were unaffected by iron status. This experiment demonstrates a functional consequence of iron-deficiency anemia in the balance of heat production and loss and suggests that thyroid-hormone metabolism may be responsible.