- Is most commonly caused by parathyroid adenoma
- is characterized by the following:
a) increased serum [Ca2+] (hypercalcemia)
b) decreased serum [phosphate] (hypophosphatemia)
c) increased urinary phosphate excretion (phosphaturic effect of PTH)
d) increased urinary Ca2+ excretion (caused by the increased filtered load of Ca2+)
e) increased urinary cAMP
f) increased bone resorption

- In addition to its role in calcium metabolism, parathyroid hormone in excess stimulates unchecked osteoclastic erosion of bone, particularly subperiosteally and later endosteally.