A 72-year-old woman with long history of type-2 DM presents with abdominal pain. Physical examination reveals neuromuscular weakness and hypeension. Laboratory studies show markedly reduced serum calcium and elevated PTH. A surgical exploration of the patient's neck demonstrates 4 symmetrically enlarged parathyroid glands. This patient's endocrinopathy may be caused by which of the following underlying disorders?
Adrenal insufficiency Chronic liver disease Insulin deficiency Renal insufficiency