Postpartum thyroiditis (PPT) occurs in 5%-9% of unselected postpartum women; hyperthyroidism and hypothyroidism develop, the latter being permanent, in up to 25 %-30% of women. PPT is strongly associated with antithyroid peroxidase (anti-TPO) antibodies, but 50% of anti-TPO positive women do not develop thyroid dysfunction. Symptom analysis has shown that lack of energy and irritability were the most frequent hyperthyroid symptoms whereas lack of energy, aches and pains, poor memory, dry skin, and cold intolerance were the significant hypothyroid features. Some of these symptoms were more frequently observed than in antibody-negative controls even when these patients were euthyroid and in anti-TPOAb positive women who did not develop PPT at all. The diagnosis of PPT is based on the observation of abnormal thyroid function tests in a postpartum anti-TPOAb-positive woman: transient hyperthyroidism occurs at 14 weeks and hypothyroidism at 19 weeks postpartum. Diffuse or multifocal hypoechogenicity of the thyroid is seen on echography and a thyroid destructive process is evidenced by an increase in serum thyroglobulin and urinary iodine excretion. In addition to the 25%-30% of women who develop permanent hypothyroidism at 3 years, recent data indicate that 50% of women who have developed PPT will be hypothyroid 7-9 years later. The long-term risk is only 5% for those anti-TPOAb positive women not developing thyroid dysfunction postpartum. The risk of recurrent PPT is 70% if previous PPT was experienced and 25% if the patient was euthyroid after the first pregnancy.