Postpartum thyroiditis: epidemiology and clinical evolution in a nonselected population.

Postpartum thyroiditis (PPT) presents in approximately 5% of women. Its incidence, clinical characteristics, and evolution were studied in a nonselected population of Mediterranean women. Six hundred five healthy women, recruited between the 36th week of pregnancy and the 4th postpartum day, underwent initial clinical and biological evaluation and postpartum at 1 (n = 605), 3 (n = 552), 6 (n = 574), 9 (n = 431), and 12 (n = 444) months. PPT was diagnosed in women with transient hyperthyroidism between 1 and 3 months postpartum and/or hypothyroidism between 3 and 6 months postpartum. Permanent hypothyroidism was considered if it was overt and persisted one year after diagnosis. The incidence rate of PPT was 7.8%. Eighty-two percent of PPT patients had hormone abnormalities at the 6th month postpartum, 8.8% showed depression and 51% goiter. PPT was manifest as hyperthyroidism plus hypothyroidism in 35.5% of patients, because only transient hyperthyroidism in 22.2% and as hypothyroidism alone in 42.3%. Five patients with hypothyroidism during PPT (0.82% of the initial population, 11.1% of PPT patients, and 15.6% of hypothyroidism PPT patients) presented permanent hypothyroidism after a follow-up of 39.8 (4.2) months. PPT was found in 7.8% of general Mediterranean population. We recommend evaluation at the 6th postpartum month to diagnose the majority of PPT women and indefinite follow-up of hypothyroid PPT patients to detect permanent hypothyroidism.