Abstract
The effect of hemithyreoidectomy on the hyperplastic response of the remaining thyroid lobe in hypophysectomized rats was examined using stathmokinetic and radiochemical methods. It was demonstrated that the proliferogenic reaction of the thyroid lobe after removal of the contralateral lobe, although weaker, occurs also in hypophysectomized rats. The pituitary, although playing an essential role in the compensatory thyroid hyperplasia following hemithyreoidectomy, is not required in this case.