A 44-year-old woman presents to the clinic feeling tired and fatigued all the time. She gained 30 pounds of weight despite dieting. She has also noticed an increasing problem with constipation despite adequate fiber intake.She is frequently cold when others are hot. Her menses have become irregular and heavy. Her current medications include lisinopril, amiodarone, atorvastatin, ibuprofen and claritin. On physical examination, her vitals reveal BP 165/98 mm Hg, P 55 bpm, R 20, and T 37°C. She is in no acute distress and appears in good health. She has a slightly enlarged, nontender thyroid noted on her neck. She has proximal muscle weakness. Her reflexes are diminished. The skin is cool, dry, and rough. The heart sounds are quiet. The rectal and pelvic examinations show no abnormalities, and the stool is negative for occult blood. You check her thyroid function, and her TSH is elevated and free T4 is low. What is the most likely cause of this patient’s condition?
