Follow-up Study Of 58 Patients Diagnosed As Postpartum Thyroiditis

ObjectiveTo investigate the cumulative incidence of persistent hypo- thyroidism in patients who diagnosed as postpartum thyroiditis (PPT) and determine the factors associated with the development of persistent hypothyroidism in those patients. We also aimed to observe the dynamic change of thyroid antibodies in the PPT patients.MethodsThe present study was performed as the continuous study following the former epidemiological survey on PPT, in which 58 patients with PPT (35 overt PPT and 23 subclinical PPT) were diagnosed. The 58 patients were followed up at 12th month postpartum, and then every 6 months until 24 months postpartum. Patients were taken fasting blood samples for testing serum TSH, thyroid peroxidase antibody (TPGAb), thyroglobulin antibody (TgAb). Free T3 (FT3), free T4 (FT4) and TRAb were detected if TSH was abnormal.ResultsOf the total 58 PPT patients, 91.4% (n=53) were successfully followed. 5 patients with overt PPT and 6 patients with subclinical PPT developed persistent hypothyroidism, that was, the cumulative incidence of persistent hypothyroidism in the studied PPT patients was 20.8%. Among 15 PPT patients who had a classical biphasic course (a thyrotoxic phase followed by a hypothyroid phase), persistent hypothyroidism was seen in 26.7% (n=4). Among 11 PPT patients with hypothyroidism only, persistent hypo- thyroidism was seen in 63.6% (n=7). On the contrary, none of the patients with thyrotoxicosis only had persistent hypothyroidism. All of the patients who developed persistent hypothyrodism had a higher TSH levels than 4.8 mU/L. Before delivery, TSH levels of the patients developed persistent hypothyroidism were significantly higher than those of the patients with transient hypothyroidism, and the similar thing happened at the 12th month postpartum (all P<0.01). PPT patients maintained a relatively higher rate of thyroid autoantibodies. The positive rate of TPOAb at the 12th, 18th and 24th month postpartum was 56.6%, 50.9% and 52.8%, respectively; and the positive rate of TgAb, 35.8%, 30.2% and 30.2%, respectively. Both the positive rate and titer of TPOAb in patients with overt PPT were higher than those in patients with subclinical PPT (P＜0.05).ConclusionsWe followed up 58 patients with PPT for 2 years postpartum, their cumulative incidence of persistent hypothyroidism was 20.8%. Whether a patient with PPT would develop persistent hypothyroidism depends on their manifestation during the course of disease and their TSH levels. It is necessary to screen PPT, and screening at the 6th month postpartum should be reasonable.