Nickan Research Institute Journal of Parathyroid Disease 2345-6558 2 1 2014 01 01 Normal alkaline phosphatase level in a patient with primary hyperparathyroidism due to parathyroid adenoma 47 50 EN Behzad Einollahi Mehrdad Taghipour Mohsen Motalebi Mahdi Ramezani-Binabaj Journal Article Primary hyperparathyroidism is relatively an uncommon condition, where the majority of cases present asymptomatically after biochemical testing showing a mild hypercalcemia and elevated parathyroid hormone (PTH) level. Long-standing elevated serum calcium level can lead to renal insufficiency. High serum PTH levels are associated with elevated alkaline phosphatase (ALP) levels in the general population. We present, an 89-year-old woman who initially manifested acute renal failure due to hypercalcemia and, finally, was diagnosed parathyroid adenoma. An interesting issue that drew our attention was the elevation of serum PTH level, despite the normal serum ALP concentration. It is the most important topic in this presentation. According to direct relationship between serums intact PTH and ALP in primary hyperparathyroidism, any failure in increasing levels of ALP, draw our attention to a range of diseases. Differential diagnoses for low ALP activity are mentioned in this case report.