Postpartum thyroid dysfunction: a state of immunological dysregulation

Postpartum thyroid dysfunction (PPTD) occurs in the first 12 months after delivery. This work was designed to compare thyroid peroxidase (TPO) and thyroglobulin (Tg) autoantibodies for determination of the diagnosis and, also, to detect role of lymphocytes in the pathogenesis of autoimmune thyroiditis.

This study was conducted on 50 females in postpartum period. Thyroid hormones, TPO- and Tg-Abs, and percentages of blood lymphocytes were determined.

The TPO-Abs were positive in 1(4%),10 (66.7%),6 (60%) of the control, hyperfunction, and hypofunction groups, respectively. The Tg-Abs were positive in 1(4%), 8 (533%), 5 (50%) of same groups, respectively. There was significant negative correlation between serum FT4 and TPO and Tg antibody titers in the hypofunction group. In cases with positive TPO-Abs, there were significantly decreased natural killer cells (NK) and significantly increased activated T cells when compared to the control group and to the TPO negative cases.

The TPO Ab was more sensitive than Tg Ab in predicting PPTD and a high titer of both correlates with the severity of hypothyroidism. Two forms of PPTD appeared to exist: autoimmune form characterized by positive TPO-Ab and increased activated T cells and reduced NK cells and a non immune form without these characteristics.