THE INFLUENCE OF THIOURACIL ON REPRODUCTION AND GROWTH IN THE RAT

Abstract

Fertility is markedly reduced in adult female rats rendered hypothyroid by a diet containing 0.2% thiouracil fed for 10 wks. This was explained on the basis of altered estrus cycles. Cretinoid young were obtained from these females and were maintained at a stage of incomplete development for periods up to 16 mos. by continuing the diet of 0.2% thiouracil. These animals have large, colloid-free thyroids, low plasma protein iodide values and B. M. R.''s lowered by 20-35%. The withdrawal of the thiouracil results in a temporary renewal of growth and a rapid restoration of reproductive activity. The thyroid recovers its ability to store thyroglobulin and to restore the B. M. R. The plasma level of hormone does not return to normal.