A 55-year-old man presents with muscle aches and weakness, along with joint pain. He also reports constipation and feeling more tired than usual. On examination, his reflexes are delayed. What are the potential causes, and what are the next steps?
The symptoms of muscle aches, weakness, joint pain, constipation, and fatigue could suggest hypothyroidism. Other potential causes could include fibromyalgia, arthritis, or a muscle disease. The next step would be to order thyroid function tests, including serum TSH and free T4 levels.