Unilateral posterior deafferentation of hypothalamus and mitotic activity of thyroid follicular cells under normal conditions and after hemithyroidectomy.

The effect of unilateral posterior deafferentation of the hypothalamus on the mitotic activity of thyroid follicular cells was studied in hemithyroidectomized and sham-operated rats. Left side posterior deafferentation of the hypothalamus reduced significantly the basal mitotic activity of both thyroid lobes and prevented the hemithyroidectomy-induced increase in mitotic activity of the remaining thyroid lobe. Right side posterior deafferentation of the hypothalamus or sham operation did not interfere with the normal or stimulated activity of the follicular cells. These data suggest left side dominance in the mitosis control of the thyroid cells but the mechanism resulting in these findings remains unclear.