The most common cause of severe hypercalcemia is-
Vitamin D toxicity
Sarcoidosis
Chronic renal failure
Malignancy
Causes of hypercalcaemia are listed in Box 20.36. Of these, primary hyperparathyroidism and malignant hypercalcaemia are by far the most common. Familial hypocalciuric hypercalcaemia (FHH) is a rare but impoant cause that needs differentiation from primary hyperparathyroidism (HPT). Lithium may cause hyperparathyroidism by reducing the sensitivity of the calcium-sensing receptor. Causes of hypercalcaemia- With normal or elevated PTH levels *Primaryoeiaryhyperparathyroidism *Lithium-inducedhyperparathyroidism *Familialhypocalciuric hypercalcaemia With low PTH levels *Malignancy(lung,breast,myeloma,renal,lymphoma, thyroid) *Elevated1,25(OH)2vitaminD(vitaminDintoxication, sarcoidosis,HIV,othergranulomatousdisease) *Thyrotoxicosis *Paget'sdiseasewithimmobilisation *Milk-alkalisyndrome *Thiazidediuretics *Glucocoicoiddeficiency DAVIDSONS PRINCIPLE AND PRACTICE OF MEDICINE 22ND EDITION PAGENO-767
Endocrinology