Effects of Vitamin B 12 on Thiouracil Action in Rats. †

Summary

The effects of crystalline vit. B₁₂ on thiouracil action was determined in immature female rats for a 30-day period. The vitamin completely counteracted the growth-inhibiting action of thiouracil, and this was accompanied by a considerable increase in food consumption. Although vit. B₁₂ decreased the thyroid hypertrophy induced by thiouracil, the uptake of radioactive iodine (I¹³¹) by the thyroids was even less than in the rats which received thiouracil only. It is suggested that vit. B₁₂ may be able to induce normal growth in hypothyroid rats.