A 69-year-old woman comes to the physician for a follow-up appointment. Laboratory studies are performed. Serum parathyroid hormone (PTH) versus calcium are shown below. Which of the following is the most likely explanation for these findings?
Hypoparathyroidism
Multiple endocrine neoplasia type I (MEN 1)
Osteoporosis
Renal cell carcinoma
Vitamin D receptor insensitivity
