<prompt> Which of the following is a feature of primary hyperparathyroidism ?Reversible growth of parathyroid glandIrreversible growth of parathyroid glandHypercalcemia and hyperphosphatemiaHypocalcemia and hyperphosphatemia  <response>: Primary hyperparathyroidism is caused by autonomous secretion of PTH, usually by a single parathyroid adenoma, which can vary in diameter from a few millimetres to several centimetres. It should be distinguished from secondary hyperparathyroidism, in which there is a physiological increase in PTH secretion to compensate for prolonged hypocalcaemia such as in vitamin D deficiency, p. 1126, and from teiary hyperparathyroidism, in which continuous stimulation of the parathyroids over a prolonged period of time results in adenoma formation and autonomous PTH secretion Box 20.39. This is most commonly seen in individuals with advanced chronic kidney disease. DAVIDSONS PRINCIPLES AND PRACTICE OF MEDICINE 22ND EDITION PAGE NO-769 