Dynamic changes of IgG subtypes of thyroid peroxidase antibody in patients with postpartum thyroiditis.

AIM: To clarify dynamic changes of IgG subtypes of thyroid peroxidase antibody (TPOAb) during the first postpartum year in Chinese patients diagnosed with postpartum thyroiditis (PPT).

METHODS

We retrospectively collected serum samples before and 3, 6, 9 and 12 months postpartum from 58 PPT patients. Levels of TPOAb and its IgG subtypes were examined by ELISA.

RESULTS

Titers of total TPOAb and its IgG subtypes were lowest before delivery in PPT patients. Following delivery, titers of total TPOAb increased. Concentrations of IgG1 and IgG4 subtypes increased for 3 months postpartum, then became stable. Concentrations of the IgG2 subtype increased gradually until 9 months postpartum. Concentrations of the IgG3 subtype reached a peak at 6 months postpartum and remained at a high level thereafter. In PPT patients with an episode of hypothyroidism, levels of total TPOAb and of the IgG subtypes as well as the IgG1/IgG4 ratios were significantly higher than those in patients with an episode of hyperthyroidism and normal controls. Correlations between titers of TPOAb and thyroid-stimulating hormone levels (positive) and free T(4) levels (negative) were seen 6 months postpartum.

CONCLUSION

TPOAb is related to thyroid injury and the IgG1 subtype of TPOAb may play a major role in the damage of the thyroid in PPT.