PTH and primary hyperparathyroidism: Primary hyperparathyroidism (PHPT) is the third most common endocrine pathology in which there is increased secretion of PTH with resultant elevated serum calcium levels due to causes intrinsic to parathyroid gland, such as a solitary adenoma (commonest cause with 80–85% incidence), multiglandular parathyroid disease (previously known as hyperplasia, with 10–15% incidence), atypical parathyroid tumour (previously known as atypical adenoma, with 1.2–1.3% incidence), and parathyroid carcinoma (0.1–5% incidence) [1,2,3].