Parathyroid Hormone Related Peptide (PTHrP): A Mini-Review

In most clinical situations hypercalcemia is caused by primary hyperparathyroidism (PHP) or malignancy [1,2]. Because the excretion of urinary cAMP (cyclic 3’,5’ adenosine monophosphate) has been proved to be a good measurement of the biological activity of parathyroid hormone (PTH) in PHP some investigators started measuring urinary cAMP excretion in hypercalcemic patients with a malignant tumor in an attempt to differentiate between the hypercalcemia of PHP and of malignancy [3-5]. Soon it appeared that a considerable part of patients with Hypercalcemia of Malignancy (HHM) also showed an increased urinary cAMP excretion. This was found in particular in hypercalcemic patients without bone metastases (6-8). Like in PHP these patients also had a decreased tubular reabsorption of phosphate (TmPO4/ GFR). However in contrast to patients with PHP normal or low levels of 1.25. di-(OH)D3 were found and the tubular reabsorption of calcium was not increased [8].