USMLE (United States Medical Licensing Examination) Step 1 Practice Exam

Which type of thyroiditis presents with abrupt onset of thyrotoxicosis postpartum and progresses to primary hypothyroidism?

1. Follicular adenoma

2. Graves hyperthyroidism

3. Riedel thyroiditis

4. Subacute painless lymphocytic thyroiditis

The correct answer is: Subacute painless lymphocytic thyroiditis

Subacute painless lymphocytic thyroiditis, often referred to as postpartum thyroiditis, typically occurs in women after childbirth and is characterized by an initial phase of thyrotoxicosis. This condition arises due to the immune-mediated destruction of thyroid tissue, which leads to the release of stored thyroid hormones into the circulation, causing symptoms of hyperthyroidism shortly after delivery. The unique aspect of this thyroiditis is that it often progresses to primary hypothyroidism. In this later phase, the thyroid gland becomes depleted of its hormone stores due to the inflammatory process and subsequent damage, resulting in insufficient production of thyroid hormones and leading to symptoms of hypothyroidism. The abrupt onset of symptoms postpartum is a distinguishing feature, making this type of thyroiditis particularly notable for its timing and progression. This condition typically resolves within a year, and in some cases, the thyroid function may return to normal. However, a subset of women may develop long-term hypothyroidism. Understanding the clinical course of subacute painless lymphocytic thyroiditis helps healthcare providers manage and recognize the signs and symptoms of this postpartum condition effectively.