Calcium metabolism is regulated by three specific hormones: parathor- mone, calciferol metabolites, and calcitonin. Cyclic AMP also plays an important part in calcium regulation, and its concentration in urine can be taken as a measure of parathyroid function. Methods for quantitative measurement of, e.g. calcium-regulating hormones and vitamin D metabolites as well as of cAMP are absolutely necessary for safe differential diagnosis of diseases of the parathyroid like hypo- and hyperparathyroidism. In this monograph all presently available methods are summarized as to whether they can already...