This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Parathyroids, Subject name: Pathology
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? 
Select and explain. 
A. Adrenal insufficiency, B. Chronic liver disease, C. Insulin deficiency, D. Renal insufficiency
D: Renal insufficiency
Answer: D: Renal insufficiency 
Explanation: - Given clinical features suggests the diagnosis of secondary hyper-parathyroidism Secondary hyper-parathyroidism -Depicted as CB Calcium ,| PTH - Causes: Chronic renal failure Vitamin D deficiency Intestinal malabsorption Fanconi syndrome -Diabetic glomerulosclerosis is a major cause of renal insufficiency. -Chronic hypocalcemia & retention of phosphate-Compensatory hypersecretion of PTH in renal failure. - As a result, secondary hyperplasia of all parathyroid glands occurs. Enlarged parathyroid glands occasionally become independently hyperfunctional resulting in teiary hyperparathyroidism. Primary hyperparathyroidism is caused by parathyroid adenoma/ hyperplasia/ carcinoma.