Normal alkaline phosphatase level in a patient with primary hyperparathyroidism due to parathyroid adenoma

Introduction Primary hyperparathyroidism as a condition with a high bone turnover is caused by an increased secretion of parathyroid hormone (PTH). It is usually originated from a solitary parathyroid adenoma. PTH through its complex actions on the kidneys, gastrointestinal tract, and the bones is involved in the hemostasis of vitamin D, calcium, and phosphate (1). Primary hyperparathyroidism occurs with no symptoms in up to 80% of patients and increased levels of PTH are characterized during work up of hypercalcemia (2). Long-standing elevated serum calcium level can lead to renal insufficiency which is dependent to duration and degree of hypercalcemia. Generally hyperparathyroidism is diagnosed through parathyroid immunoassay. When high PTH has been confirmed, the high serum level of calcium is confirmatory factor for primary hyperparathyroidism. Other biochemical agents are measured here in these cases such as: serum alkaline phosphatase (ALP) which is often elevated, serum chloride/phosphate ratio (33 or more in most patients), serum phosphate, urinary cAMP and intact PTH (iPTH) levels that are elevated too. Decrease in serum level of this enzyme is less considered than its increase. Here we describe a patient with elevated serum PTH level due to primary hyperparathyroidism who had a low serum ALP and discuss about the causes can lead to these clinical conditions. Some other interesting features of this case such as acute renal failure (ARF) due to primary hyperparathyroidism are also discussed. To our knowledge this is the first such reported case in Iran.