Which of the following is associated with secondary hyperparathyroidism

Answer is C (Chronic renal failure): Conditions leading to decrease in serum calcium levels cause a compensatory increase in secretion of PTH resulting in secondary hyperparathyroidism. Amongst the options provided chronic renal failure is one such cause of secondary hyperparathyroidism. Primary hyperparathyroidism Elevated PTH due to increased PTH secretion from an intrinsic abnormality of one or more parathyroid glands This is most commonly due to solitary adenoma involving one gland Secondary hyperparathyroidism Excessive secretion of PTH by parathyroids secondary to a lowered serum ionized calcium This is a compensatory hyperplasia of all four glands aimed at correcting lowered serum calcium Ectopic parathyroid hormone syndrome Ectopic PTH syndrome results from the production by several malignant neoplasms of PTH related peptide