[Stages of the etiological diagnosis of hypercalcemia]

After confirming hypercalcemia by 3 successive measurements of the total plasma calcium corrected for a plasma protein concentration of 72 g/l, which excludes spurious hypercalcemia due to dehydration, the physician orientates the aetiological diagnosis bearing in mind that primary hyperparathyroidism PHPT is the cause of 85 p. 100 of all asymptomatic forms of hypercalcaemia whilst overt or occult malignancy is the main cause (60 p. 100) of symptomatic forms of hypercalcaemia with PHPT responsible for 20 p. 100 of cases. Other causes, including drug toxicity with Vit D, calcium, Vit A, lithium, thiazide and aluminium hydroxide, sarcoidosis, hyperthyroidism, Addison's disease, pheochromocytoma and familial endocrine disorders are much rarer. Nevertheless, these rarer causes must be excluded on the clinical history and examination followed by radiological (chest X ray, plain abdomen X ray, bone X rays) and simple biological tests. The latter and/or scans tests should also help in a rapid diagnosis of metastatic carcinoma and multiple myeloma, so that the major diagnostic problem is to distinguish primary HPT from occult malignancy. This problem is greatly facilitated by reliable assays of C terminal or medium PTH rather than renal CAMP which is increased in 80 p. 100 of occult malignancies. When PTH assays is unavailable or unreliable Dent's hydrocortisone suppression test may be useful as a fall in'serum calcium is associated with occult malignancy in 70 p. 100 of cases and non-suppression is associated with PHPT in 91 p. 100 of cases. Discriminant analysis of the usual biochemical parameters may be helpful in this differential diagnosis and is accurate in about 90 p. 100 of cases. However, the association of PHPT and malignancy is also possible and not fortuitous.