User:Nicole.dilo94/sandbox

Causes
Hypoparathyroidism is a common cause of hypocalcemia. Calcium is tightly regulated by the parathyroid hormone (PTH). In response to low calcium levels, PTH levels rise, and conversely if there are high calcium levels then PTH secretion declines. However, in the setting of absent, decreased, or ineffective PTH hormone, the body loses this regulatory function, and hypocalcemia ensues. Hypoparathyroidism is commonly due to surgical destruction of the parathyroid glands. Hypoparathyroidism may also be due to autoimmune problem. Some causes of hypocalcaemia are as follows: • Hyperphosphatemia

• Vitamin D deficiency

• Chronic liver disease

• Edetate disodium

• Magnesium deficiency

• Prolonged use of medications/laxatives (magnesium)

• Osteomalacia

• Chronic kidney failure

• Ineffective active vitamin D

• Hypoparathyroidism/genetic

• After surgery hypoparathyroidism

• Hungry bone syndrome

• Tumour lysis syndrome

• Acute kidney injury

• Rhabdomyolysis (initial stage)

• As a complication of pancreatitis

• Alkalosis

• Massive red blood cell transfusion due to excess citrate in the blood

• As blood plasma hydrogen ion concentration decreases, caused by respiratory or metabolic alkalosis, the concentration of freely ionized calcium, the biologically active component of blood calcium, decreases. Because a portion of both hydrogen ions and calcium are bound to serum albumin, when blood becomes alkalotic, the bound hydrogen ions dissociate from albumin, freeing up the albumin to bind with more calcium and thereby decreasing the freely ionized portion of total serum calcium. For every 0.1 increase in pH, ionized calcium decreases by about 0.05 mmol/L. This hypocalcaemia related to alkalosis is partially responsible for the cerebral vasoconstriction that causes the lightheadedness, fainting, and paraesthesia often seen with hyperventilation.

• Neonatal hypocalcemia

• Gain of function mutations of the calcium-sensing receptor

• Foscarnet use

• Loop diuretic use

• Crohn disease

• High level of lactic acid in the blood

• Pseudohypoparathyroidism

Mechanism
Physiologically, blood calcium is tightly regulated within a narrow range for proper cellular processes. Calcium in the blood exists in three primary states: bound to proteins (mainly albumin), bound to anions such as phosphate and citrate, and as free (unbound) ionized calcium; all of these forms are ionised. Only the unbound calcium is physiologically active. Normal blood calcium level is between 8.5 to 10.5 mg/dL (2.12 to 2.62 mmol/L) and that of unbound calcium is 4.65 to 5.25 mg/dL (1.16 to 1.31 mmol/L).