Thyroid Disorders USMLE Step 1 Practice Question
A 35-year-old woman on levothyroxine 75 mcg daily for hypothyroidism reports persistent fatigue and myalgias despite a normal TSH of 2.1 mIU/L 6 weeks ago. She takes her medication with breakfast and her calcium supplement. Recent labs show TSH 6.8 mIU/L and free T4 0.9 ng/dL. Which of the following is the most likely cause of her worsening symptoms?
Answer choices
- AMalabsorption of levothyroxine due to calcium supplement interferenceCorrect answer
- BDevelopment of secondary hypothyroidism from pituitary insufficiency
- CNoncompliance with levothyroxine therapy
- DThyroid hormone resistance syndrome
- EGraves' disease superimposed on treated hypothyroidism
- FProton pump inhibitor use reducing gastric acidity for levothyroxine absorption
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