Pituitary is not required for the compensatory thyroid hyperplasia.

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