Clinical VignetteQuestion 1 of 21
Bigger Hat Problem
A 67-year-old man of English descent presents for evaluation of a right leg that has become progressively bowed over the past 3 years. He reports needing to purchase hats two sizes larger than he did a decade ago and has noticed increasing difficulty hearing out of his right ear. On examination, the right tibia is enlarged, warm to touch, and bowed anteriorly. Neurologic examination is intact. Laboratory results:
| Test | Result | Reference |
|---|---|---|
| Serum calcium | 9.4 mg/dL | 8.5–10.5 |
| Phosphate | 3.6 mg/dL | 2.5–4.5 |
| PTH | 38 pg/mL | 15–65 |
| Alkaline phosphatase (ALP) | 618 U/L | 44–147 |
| 25-OH-vitamin D | 31 ng/mL | 30–100 |
| GGT | 22 U/L | 8–61 |
| Creatinine | 0.9 mg/dL | 0.7–1.3 |
Which of the following is the most likely diagnosis?