INFLUENCE OF ALIMENTARY IRON-DEFICIENCY ON PARAMETERS OF THYROID-HORMONE METABOLISM IN RATS

The effect of iron deficiency an parameters of thyroid hormone metabol ism was examined in two experiments with 24 male weanling Sprague-Dawl ey rats. The animals were led a semisynthetic diet based on casein, co ntaining either 9 mg Fe/kg (iron-deficient diet) or 60 mg Fe/kg (contr ol diet). In experiment 1, all animals had free access to food. As foo d consumption in the iron-deficient animals was significantly decrease d in contrast to controls, pair-feeding was introduced in experiment 2 to guarantee equal levels of consumption. Experiments 1 and 2 lasted for 40 days. In both experiments, iron-deficient rats had a lower live body weight at the end of the trial, and had an impaired feed-efficie ncy ratio. Concentrations of haemoglobin and haematocrit, erythrocyte count, and MCV were lowered by iron deficiency. Iron-deficient rats ha d lower concentrations of T-3 (experiment 1, - 42%; experiment 2, - 16 %), T-4, (experiment 1, - 38%; experiment 2, - 78%), and fT(4) (experi ment 1, - 15%; experiment 2, - 67%) than ad libitum- and pair-fed cont rol rats. Iron deficiency impaired the activity of hepatic deiodinase. In the second experiment, this enzyme's activity was lowered by 75% i n iron-deficient rats. and in che first experiment, the activin was ev en below the detection limit in iron-deficient rats. The results of th is investigation demonstrate that iron might play a role in thyroid-ho rmone metabolism, especially via hepatic deiodinase activity.