TY - JOUR A1 - , T1 - Sex-related effects of hypothyroidism on cellular proliferation in the hypophyseal mammotroph population of the rat JO - Eur. J. Anat. SN - 1136-4890 Y1 - 2008 VL - 12 SP - 145 EP - 151 UR - http://www.eurjanat.com/web/paper.php?id=08030145 KW - - N2 - Changes in the morphology and number of prolactin-immunoreactive cells have been described in hypothyroidism. However, no analyses of the changes that occur in the proliferation of these cells have been undertaken. In order to determine the proliferation rate of rat hypophyseal prolactin cells in hypothyroidism and whether the observed changes are related to increases in TRH, a double immunohistochemical study for PCNA and prolactin was carried out in thyroidectomised rats and in rats treated with TRH. TRH treatment, but not thyroidectomy, increased the percentage of prolactin-producing cells in both sexes (p<0.01). However, whereas the cellular proliferation of prolactin-producing cells was significantly increased in males (p<0.01) in both experimental designs, in female rats the proliferation of prolactin-producing cells was increased after treatment with TRH, but not in thyroidectomised rats (p<0.01). Our results demonstrate - mainly in male rats - that modifications in the hypophyseal-thyroid axis elicit changes in prolactin-producing cells that are related to the proliferation rate of these cells. These results suggest that sex-related effects of both TRH and thyroid hormones could be involved in the physiological regulation of the proliferation of pituitary prolactin-producing cells, because the responses to treatment with TRH were different from the changes observed in thyroidectomised rats. ER -