Catecholamines cause the hypercalciuria and hypercalcaemia in phaeochromocytoma and in hyperthyroidism.

Catecholamines induce bone resorption and hypercalcaemia by the beta-adrenergic effect in bone and hypercalciuria by the alpha adrenergic effect in kidney. The interplay between the alpha-adrenergic hypercalciuria and beta-adrenergic hypercalcaemia explains why in some, but not all, phaeochromocytomas hypercalcaemia occurs. The hypothesis predicts hypercalciuria in both phaeochromocytoma and neuroblastoma. In hyperthyroidism, negative calcium balance and hypercalcaemia cannot be attributed to the direct effect of thyroid hormones on the bone but can be explained by augmentation of the catecholamine effects on bone and kidney by thyroid hormones. The hypothesis offers a solution for an apparent paradox in hyperthyroidism of increased urinary cAMP while nephrogenous cAMP is decreased. It also explains why propranolol corrects hypercalcaemia without influencing renal calcium loss.