Enhanced differentiation of sexually dimorphic organs in L-thyroxine treated Tfm mice

In the present study we examined the effects of L-thyroxine on the differentiation of three sexually dimorphic organs in mice affected by the testicular feminization mutation (Tfm): the submaxillary salivary glands, the kidneys, and the adrenal glands. In the salivary gland we compared the effects of L-thyroxine and testosterone in normal and Tfm mice on the morphology of the intercalated tubules and on the NGF content of this gland. In the kidney we examined thyroid hormone effects on the sexually dimorphic proximal convoluted tubules. In the adrenal gland we studied the effects of the same hormone on the weight of the organ and on the structure and ultrastructure of the zona reticularis in untreated and L-thyroxine treated Tfm mice. The results show that the thyroid hormone enhances differentiation of the dimorphic structures in all these organs and increases the secretory activity of the salivary and adrenal glands. The stimulatory effects of L-thyroxine are more pronounced on the weight of the adrenal than of the salivary gland and of the kidney. Our results raise the question whether the enhanced differentiation elicited by L-thyroxine in the three sexually dimorphic organs of Tfm mutants is due to a direct hormonal effect, or whether it is fully, or in part, mediated through the hypothalamo-pituitary-thyroid axis.