AJP - Regulatory, Integrative and Comparative Physiology, Vol 239, Issue 5 377-R381, Copyright © 1980 by American Physiological Society
Hypothermia in iron deficiency due to altered triiodothyronine metabolism
E. Dillman, C. Gale, W. Green, D. G. Johnson, B. Mackler and C. Finch
Iron-deficient rats become hypothermic and have an excessive catecholamine
response when exposed to an ambient temperature of 4 degrees C. This is not
due to changes in body insulation, since thickness is unaltered, since
differences persist after removal of hair, and since cutaneous
vasoconstriction is intact. On the other hand, oxygen consumption of
iron-deficient animals at 4 degrees C is reduced, 39 +/- 3 ml . kg-1 .
min-1 compared to 63 +/- 2 in control animals. Thyroxine (T4) values at 4
degrees C were 4.34 +/- 0.20 microgram/dl sera as compared to control
values of 3.6 +/- 0.32. Triiodothyronine (T3) values of iron-deficient
animals in the cold were 48 +/- 6.8 ng/dl as compared to 72 +/- 5.6 in
control animals. Treatment of iron-deficient animals with iron was shown to
normalize the plasma T3 response at 4 degrees C within 6 days.
Thyroidectomized iron-deficient animals injected with T3 did not show
hypothermia at 4 degrees C, whereas thyroidectomized iron-deficient animals
injected with T4 showed hypothermia, increased catecholamines, and
decreased T3 levels as compared to non-iron-deficient animals similarly
treated. It is proposed that iron deficiency impairs conversion of T4 to T3
and that this is primarily responsible for the hypothermia observed.
