The correlation of thyroid autoimmunity and peripheral and uterine immune status in women with recurrent miscarriage

Thyroid autoimmunity (TAI), which is the most prevalent cause of thyroid dysfunction in women of reproductive age, is associated with increased risk of miscarriages and adverse pregnancy outcomes. However, the exact pathophysiology of TAI is still unknown. We aim at investigating the relationship between TAI and the peripheral and uterine immune markers in women with recurrent miscarriage (RM). Peripheral blood and endometrial tissue samples were collected during mid-luteal phase of 242 RM women to evaluate the prevalence of TAI, the thyroid function, the percentages of peripheral blood and endometrial lymphocytes, the levels of peripheral blood T helper 1 (Th1) cytokine and natural killer (NK) cell cytotoxicity. There was no relationship between TAI and peripheral immune parameters. However, the percentage of endometrial Regulatory T (Treg) cells was significantly higher in RM women who were thyroid antibody positive than in those who were antibody negative (p < 0.05). Thyroid antibody positivity seems to be part of a more generalized immune dysfunction. The increased endometrial Treg cells in RM patients with TAI may ameliorate coincidental TAI during pregnancy by linked suppression and prevent the over-reactive status of the immune system.