Expression of Thyroid Hormone Receptors in Villous Trophoblasts and Decidual Tissue at Protein and mRNA Levels Is Downregulated in Spontaneous and Recurrent Miscarriages

Thyroid hormones are essential for the maintenance of pregnancy, and a deficiency in maternal thyroid hormones has been associated with early pregnancy losses. The expression of THR alpha 1, THR beta 1 and THR alpha 2 increases with gestational age. The aim of this study was the investigation of the protein and mRNA-levels of THR isoforms THR alpha 1, THR alpha 2, THR beta 1 and THR beta 2 in normal, spontaneous and recurrent miscarriages. The identification of THR-expressing cells in the decidua was done with double immunofluorescence. The nuclear expression of THR alpha 1, THR alpha 2, THR beta 1 and THR beta 2 is downregulated at protein level in spontaneous and recurrent miscarriages in villous trophoblast tissue. In decidual tissue, we found a significant downregulation only for THR alpha 1 in spontaneous miscarriages. For recurrent miscarriages, THR alpha 1 and THR beta 1 were both significantly downregulated in decidual tissue. By applying HLA-G as a trophoblast marker, we found a significant co-expression only for THR beta 2. The results of our study show that thyroid hormone receptors THR alpha 1, THR alpha 2, THR beta 1 and THR beta 2 are downregulated in spontaneous and recurrent miscarriages. The majority of cells expressing the thyroid hormone receptors in the decidua are decidual stromal cells.