A 29-year-old woman comes to the office due to unintentional weight loss, fatigue, and sweating. The patient has had no neck pain. Two months ago, she delivered a healthy boy with no perinatal complications. The patient does not breastfeed the infant. She has no chronic medical conditions and takes no medications. Blood pressure is 140/70 mm Hg, pulse is 110/min, and respirations are 16/min. Oxygen saturation is 98% on room air. Neck examination shows mild, diffuse enlargement of the thyroid gland with no tenderness. The remainder of the physical examination, including pelvic examination, is normal. Laboratory evaluation reveals low serum TSH, elevated serum thyroxine (T4), and elevated serum triiodothyronine (T3). Thyrotropin receptor antibodies are negative. Which of the following is the most likely cause of this patient's symptoms?

Question

A 29-year-old woman comes to the office due to unintentional weight loss, fatigue, and sweating.  The patient has had no neck pain.  Two months ago, she delivered a healthy boy with no perinatal complications.  The patient does not breastfeed the infant.  She has no chronic medical conditions and takes no medications.  Blood pressure is 140/70 mm Hg, pulse is 110/min, and respirations are 16/min.  Oxygen saturation is 98% on room air.  Neck examination shows mild, diffuse enlargement of the thyroid gland with no tenderness.  The remainder of the physical examination, including pelvic examination, is normal.  Laboratory evaluation reveals low serum TSH, elevated serum thyroxine (T4), and elevated serum triiodothyronine (T3).  Thyrotropin receptor antibodies are negative.  Which of the following is the most likely cause of this patient's symptoms?

Quizplus · Accepted Answer

11ec160b_3acc_6da3_9249_e5f5b0b39870_MD0001_00 This patient has weight loss, tachycardia, and a painless, diffuse goiter; her serum thyroid hormone levels are elevated and TSH is suppressed, findings consistent with primary hyperthyroidism. In light of her recent pregnancy and negative thyrotropin receptor antibody assay (which makes Graves disease unlikely) this is most likely due to postpartum thyroiditis. Postpartum thyroiditis occurs within 12 months of pregnancy and is characterized by autoimmune destruction of thyroid follicles similar to that seen in chronic lymphocytic (Hashimoto) thyroiditis. Histologic inspection demonstrates lymphocytic infiltration, sometimes with the formation of germinal centers. The breakdown of follicle margins and loss of colloid may also be seen. Postpartum thyroiditis typically begins with a hyperthyroid phase due to the release of preformed thyroid hormone, followed by a transient hypothyroid phase due to the depletion of thyroid hormone and an eventual return to a euthyroid state. (Choice A) Intake of exogenous thyroid hormone can cause thyrotoxicosis with suppression of TSH. However, thyroid enlargement would not be seen (thyroid atrophy is more typical). (Choice B) Like postpartum thyroiditis, subacute granulomatous (de Quervain/postviral) thyroiditis can have a transient hyperthyroid phase due to the release of preformed thyroid hormone. However, patients typically have low-grade fever, myalgias, and a painful, tender goiter. (Choice C) Lymphocytic hypophysitis is an uncommon disorder that may occur in postpartum women. TSH would be low due to loss of pituitary thyrotrophs, but thyroid hormone levels would also be low (ie, central/secondary hypothyroidism). (Choice E) The beta subunit of hCG shares homology with TSH and can stimulate TSH receptors on follicular cells. Gestational trophoblastic neoplasia refers to a group of hCG-secreting tumors that most commonly occur in association with molar pregnancy (uncommon following live birth). Most patients have associated symptoms such as amenorrhea or abnormal uterine bleeding, and examination often shows uterine enlargement. Educational objective: Postpartum thyroiditis occurs within 12 months of pregnancy and is characterized by autoimmune destruction of thyroid follicles. It typically begins with a hyperthyroid phase due to the release of preformed thyroid hormone, followed by a hypothyroid phase due to depletion of thyroid hormone and an eventual return to a euthyroid state. Histologic inspection demonstrates lymphocytic infiltration with the formation of germinal centers, which is similar to chronic lymphocytic (Hashimoto) thyroiditis.

A 29-Year-Old Woman Comes to the Office Due to Unintentional