Effect of Dietary Thyroid Powder on Urinary Excretion of Formiminoglutamic Acid and Methylmalonic Acid

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Abstract
The possible role of increased food and protein intake in the action of thyroid powder in increasing the excretion of formiminoglutamic acid (FlGlu) and meth-ylmalonic acid (MMA) was studied. The food intake of all animals was measured and the protein content of the diet of the control group (without thyroid powder) was increased so that the protein intake per day per kilogram of body wt was the same for the controls and for those receiving thyroid powder in the diet. The feeding of thyroid powder produced an increase in FIGlu excretion which was not related to the increase in protein intake. The excretion of MMA which was produced by thyroid powder seemed related to the increase in protein intake caused by increased food consumption. Thyroid powder feeding had no effect on MMA excretion when protein intake was equalized. These data indicate that feeding thyroid powder affects the metabolism of vitamin B12 only as it is related to folic acid. It does not produce a generalized vitamin B12 deficiency which would have been expected to increase MMA excretion.