Hypoparathyroidism is deficiency of parathyroid hormone (PTH) which resulting in hypocalsemia and 
hyperphosphatemia. It involved calcium concentration which plays a vital role in the the pathophysiology and diagnosis of hypoparathyroidism. The following diagram shows the hydroxilation of vitamin D to its active form and its action to increase the serum calcium concentration.
Find sections such the roles of PTH, vitamin D and calcitonin, detailed explanation about pathophysiology of hypoparathyroidism, Primary hypoparathyroidism, clinical signs of hypoparathyroidism, common physical examination, hypocalcemia action potential in cardiac cells (ECG), How to diagnose primary hypoparathyroidism, and Differential Diagnosis of Hypocalcemia.
Complete read about Serum Calcium Concentration in the Pathophysiology of Hypoparathyroidism can be seen here in pdf filetype (source: vetlearn.com).
