Thyroid hormone synthesis and AITD-related inflammatory factors are modulated during early pregnancy in ewes

Pregnancy modulates the maternal thyroid to maintain endocrine and immune homeostasis. However, it remains unclear whether early pregnancy modulates thyroid hormone synthesis-related factors and autoimmune thyroid disease (AITD)-related inflammatory factors in the ovine thyroid. In this study, thyroid tissues were collected from ewes at day 16 of the estrous cycle (N16) and on days 13, 16, and 25 of pregnancy (G13, G16, and G25), and the mRNA and protein expression levels of these factors were examined by RT-qPCR, Western blot, and immunohistochemistry. The results showed that the expression of thyroid-stimulating hormone receptor increased gradually from N16 to G25, and thyroglobulin and thyroid peroxidase were significantly upregulated during pregnancy. In addition, sodium/iodide cotransporter mRNA and protein peaked at G16, and pendrin was elevated mainly at G13 and G16. However, dual oxidase 1 (DUOX1) was highest at G25, and DUOX2 peaked at G13. Furthermore, the expression of tyrosine-protein phosphatase non-receptor type 22 and tumor necrosis factor alpha peaked at G16, whereas B cell activating factor, retinoic acid receptor-related orphan receptor-γt, and interleukin (IL)-1α were reduced during pregnancy. Moreover, IL-17A mRNA and protein increased only at G25, and FOXP3 increased progressively from N16 to G25. In summary, early pregnancy modulates the expression of thyroid hormone synthesis-related factors and AITD-related inflammatory factors in a pregnancy stage-specific manner, which may be related to thyroid endocrine adaptation, immune homeostasis, and pregnancy establishment in ewes.