A 58-year-old man presents to your office because he has been having some generalized bone pains. You become concerned and send him for a blood draw. His serum studies reveal decreased calcium, increased parathyroid hormone and increased phosphate level. Radiologic survey of the patient revealed a “salt-and-pepper” skull, subperiosteal bone resorption of the second and third fingers at the proximal and middle phalanges, involvement of the distal clavicle, as well as widespread brown tumors and bone cysts.Of the following, which is the most common underlying disorder in this patient?
