<s>[INST] context: 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 . Investigations The diagnosis can be confirmed by finding a raised PTH level in the presence of hypercalcaemia, provided that FHH is excluded (p. 770). Parathyroid scanning by 99mTcsestamibi scintigraphy (Fig. 20.16) and/or ultrasound examination can be performed prior to surgery, in an attempt to localise an adenoma and allow a targeted resection. However, negative imaging does not exclude the diagnosis. DAVIDSONS PRINCIPLE AND PRACTICE OF MEDICINE 22ND EDITION PAGE NO-769 [/INST] question: Primary hyperparathyroidism is suggested by - | options: A: Increased serum calcium B: Low urinary calcium <200 C: Decreased alkaline phosphatase D: Calcitonin level | answer: A </s>