Thyroid and Vitamin B 12 Interactions in the Mouse. ∗

Abstract

Summary

1. The effects of a mild degree of induced-hyperthyroidism or vit. B₁₂ or both on growth rate were determined in 81 immature male mice fed a vit. B₁₂-deficient ration, in two experimental trials of 26 or 30 days duration. 2. Feeding .025% Protamone (iodinated casein) or 100 μg of vit. B₁₂/kilo of ration each increased the growth rate of the mice, and Protamone was more effective than vit. B₁₂ in this respect. Each substance increased food intake and enhanced the efficiency of converting food into body weight gains. When Protamone and vit. B₁₂ were fed together however, the favorable effects of either on growth were largely eliminated and efficiency of food utilization was reduced. No satisfactory explanation can be offered for this phenomenon at this time.