Causes

The exact cause of postpartum thyroiditis isn't clear. However, women who develop postpartum thyroiditis often have high concentrations of anti-thyroid antibodies in early pregnancy and after childbirth. As a result, it's believed that women who develop postpartum thyroiditis likely have an underlying autoimmune thyroid condition that flares after childbirth due to fluctuations in immune function. This underlying condition appears to be very similar to Hashimoto's thyroiditis, in which the immune system attacks the thyroid gland.