Postpartum thyroiditis is a recently described entity that often presents with symptoms of mild hypertension followed by a transient hypothyroid episode. It is associated with the presence of antimicrosomal antibodies and is thought to be autoimmune in origin. Its first appearance in susceptible women is most often in the postpartum period when it is felt that the immune system may become more active after its suppression during pregnancy. Symptoms are often mild and may be mistaken for postpartum depression or fatigue. If a patient presents with symptoms of hyper- or hypo-metabolism, thyroid function should be monitored. Although the condition is most often transient, treatment may be restricted if the patient is very symptomatic or if thyroid malfunction persists.