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Disorders of calcium metabolism

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Disorders of calcium metabolism occur when the body has too little or too much calcium. The serum level of calcium is closely regulated within a fairly limited range in the human body. In a healthy physiology, extracellular calcium levels are maintained within a tight range through the actions of parathyroid hormone, vitamin D and the calcium sensing receptor.[1] Disorders in calcium metabolism can lead to hypocalcemia, decreased plasma levels of calcium or hypercalcemia, elevated plasma calcium levels.

Disorders of calcium metabolism
Calcium
SpecialtyEndocrinology

Hypocalcemia

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Hypocalcemia is common and can occur unnoticed with no symptoms or, in severe cases, can have dramatic symptoms and be life-threatening.[1] Hypocalcemia can be parathyroid related or vitamin D related. Parathyroid related hypocalcemia includes post-surgical hypoparathyroidism, inherited hypoparathyroidism, pseudohypoparathyroidism, and pseudo-pseudohypoparathyroidism.[1] Post-surgical hypoparathyroidism is the most common form, and can be temporary (due to suppression of tissue after removal of a malfunctioning gland) or permanent, if all parathyroid tissue has been removed.[1] Inherited hypoparathyroidism is rare and is due to a mutation in the calcium sensing receptor. Pseudohypoparathyroidism is maternally inherited and is categorized by hypocalcemia and hyperphosphatemia. Finally, pseudo-pseudohypoparathyroidism is paternally inherited. Patients display normal parathyroid hormone action in the kidney, but exhibit altered parathyroid hormone action in the bone.[1] Vitamin D related hypocalcemia may be associated with a lack of vitamin D in the diet, a lack of sufficient UV exposure, or disturbances in renal function. Low vitamin D in the body can lead to a lack of calcium absorption and secondary hyperparathyroidism (hypocalcemia and raised parathyroid hormone).[1] Symptoms of hypocalcemia include numbness in fingers and toes, muscle cramps, irritability, impaired mental capacity and muscle twitching.[1]

Hypercalcemia

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Hypercalcemia is suspected to occur in approximately 1 in 500 adults in the general adult population.[2] Like hypocalcemia, hypercalcemia can be non-severe and present with no symptoms, or it may be severe, with life-threatening symptoms. Hypercalcemia is most commonly caused by hyperparathyroidism and by malignancy, and less commonly by vitamin D intoxication, familial hypocalciuric hypercalcemia and by sarcoidosis.[2] Hyperparathyroidism occurs most commonly in postmenopausal women. Hyperparathyroidism can be caused by a tumor, or adenoma, in the parathyroid gland or by increased levels of parathyroid hormone due to hypocalcemia.[2] Approximately 10% of individuals with cancer experience hypercalcemia due to malignancy.[2] Hypercalcemia occurs most commonly in breast cancer, lymphoma, prostate cancer, thyroid cancer, lung cancer, myeloma, and colon cancer.[2] It may be caused by secretion of parathyroid hormone-related peptide by the tumor (which has the same action as parathyroid hormone), or may be a result of direct invasion of the bone, causing calcium release.[2] Symptoms of hypercalcemia include anorexia, nausea, vomiting, constipation, abdominal pain, lethargy, depression, confusion, polyuria, polydipsia and generalized aches and pains.[2]

Plasma Calcium

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The amount of biologically active calcium varies with the level of serum albumin, a protein to which calcium is bound, and therefore levels of ionized calcium are better measures than a total calcium; however, one can correct a total calcium if the albumin level is known.[citation needed]

  • A normal ionized calcium is 1.12-1.45 mmol/L (4.54-5.61 mg/dL).
  • A normal total calcium is 2.2-2.6 mmol/L (9-10.5 mg/dl).
    • Total calcium of less than 8.0 mg/dL is hypocalcaemia, with levels below 1.59 mmol/L (6 mg/dL) generally fatal.
    • Total calcium of more than 10.6 mg/dL is hypercalcaemia, with levels over 3.753 mmol/L (15.12 mg/dL) generally fatal.

See also

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References

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  1. ^ a b c d e f g Murphy, E; Williams (2009). "Hypocalcemia". Medicine. 37 (9): 465–468. doi:10.1016/j.mpmed.2009.06.003.
  2. ^ a b c d e f g Waters, M (2009). "Hypercalcemia". InnovAiT. 2 (12): 698–701. doi:10.1093/innovait/inp143.
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