Effects of hypothyroidism on the karyometric development of the paraventricular and ventromedial nuclei of the hypothalamus in the mouse.

We studied the karyometric development of 4 subdivisions of the paraventricular nucleus (rostral, caudal, medial and lateral) and 3 subdivisions of the ventromedial nucleus of the hypothalamus (ventral, central and dorsal) in a hypothyroid group of male albino mice treated with propylthiouracil with or without interruption of the treatment at the 35th postnatal day. Hypothyroidism produces an increase of the nuclear-size values of the paraventricular and ventromedial nuclei, and the continued treatment increases this effect. The caudal and the rostral subdivisions of the paraventricular nucleus show more significant changes of their nuclear sizes compared to the medial and lateral subdivisions. The ventromedial nucleus responds similarly to hypothyroidism in all its subdivisions.