Decreased progestin receptors in the cerebral cortex of hypothyroid postnatal rats.

The effects of neonatal hypothyroidism were examined on the concentrations of cytosol receptors for progestin and estrogen in the cytosols from 10-day old female and male rats. The concentration of cytosol progestin- and estrogen receptors in the 10-day old female and male rats with propylthiouracil-induced hypothyroidism was determined by multiconcentration saturation analysis. Neonatal hypothyroidism markedly depressed the level of progestin receptors in the cortex but not in the hypothalamus-preoptic area (HPOA). There were no differences in the concentration of estrogen receptors in the cortex and HPOA between the control and PTU rats. These results suggest that thyroid hormone may be one of the factors affecting the development of progestin receptors in the cortex. Its significance was discussed in relation to determination of the length of sexual differentiation of the rat brain.