Effects of hormone deprivation on the karyometric development of the medial and lateral preoptic area of the male mouse. II. Hypothyroidism.

We have analysed the karyometric development of the medial and lateral preoptic area of the hypothalamus in two groups of experimentally hypothyroid male mice, from the 25th to the 160th postnatal day. In one group, animals were treated with propylthiouracil from birth until the day of sacrifice. In the second experimental group animals were treated only until the 35th postnatal day, and thereafter sacrificed at the 45th, 55th, 85th and 160th postnatal day. We compare the results of both groups of animals with a control group of male mice. Hypothyroidism did not alter the nuclear sizes of the medial preoptic area, but in the lateral preoptic area, values were significantly higher in the hypothyroid animals after the 55th day.