A 48-year-old woman is evaluated in the clinic for worsening tiredness, generalized weakness, and a 5-kg (11-lb) weight gain over the last eight months. She notes that her skin has become unusually dry, and she frequently feels cold even when others are comfortable. Her medical history is unremarkable, and she takes no medications. Vital signs are within normal limits except for a heart rate of 56/min. Physical examination reveals a diffusely enlarged, rubbery, and non-tender thyroid gland. Laboratory testing shows:
Serum TSH: 18.5 U/mL (Normal: 0.4-4.2)
Serum free T4: 0.5 ng/dL (Normal: 0.8-2.7)
Which of the following is the most likely underlying mechanism for this patient's clinical presentation?
- Autoimmune-mediated destruction of thyroid follicular cellsAnswer
- BProduction of stimulating autoantibodies against the thyrotropin receptor
- CDecreased secretion of thyrotropin from the anterior pituitary gland
- DPeripheral resistance to circulating thyroid hormones
- EGranulomatous inflammation following a viral upper respiratory infection
Answer
Autoimmune-mediated destruction of thyroid follicular cells
The correct answer accurately describes the pathophysiology of Hashimoto thyroiditis, which is the most common cause of primary hypothyroidism in iodine-sufficient areas. The patient's presentation of weight gain, fatigue, cold intolerance, bradycardia, and a diffusely enlarged, non-tender goiter is a classic clinical picture. The laboratory findings of an elevated TSH and a low free T4 confirm primary thyroid gland failure due to autoimmune-mediated destruction of the thyroid follicular cells.
Step-by-Step Solution
Key Concept
Primary hypothyroidism is characterized by an elevated TSH and low free T4, most commonly due to autoimmune Hashimoto thyroiditis.
Estimated Time:1m 0s