Q. A 50-year-old woman presents to her primary care physician with a six-month history of fatigue, muscle weakness, and bone pain. She reports that she has been feeling more tired than usual and has been experiencing muscle weakness and bone pain, especially in her arms and legs. Vital signs on presentation are BP 120/80 mm Hg, HR 80 bpm, and RR 16 bpm. The physical examination reveals a thin patient with a history of osteoporosis. Further evaluation reveals elevated levels of parathyroid hormone and calcium in the patient's blood. An ultrasound of the neck reveals a 4 cm mass in the posterior right lobe of the thyroid. What is the most likely diagnosis?