Diseases

This section is oriented around disease that affect calcium and/or phosphate levels. Because of a large number of such conditions, not all of them are discussed here.  A good website on diseases can be found under the following link:
http://www.medicinenet.com/script/main/hp.asp

 

Rickets

The disease is caused by insufficiency of vitamin D. This condition affects children, whose bones have abnormal levels of unmineralized osteoid. This leads to characteristic “bowing of legs”.

Image courtesy of: http://upload.wikimedia.org/wikipedia/commons/0/0b/Child_suffering_from_rickets.jpg 

Osteomalacia

Disease is an adult equivalent of rickets. Adults that suffer from vitamin D insufficiency have abnormal levels of unmineralized osteoid, however  “bowing” of legs does not occur, because longitudinal growth of long bones has ceased. Instead, patients affected by condition are prone to fractures as bone does not have the strength of a healthy individual. If untreated, hypocalcemia may occur due to decrease in recruitment of osteoclasts.

 

Hypercalcaemia

Disease is characterized by abnormally high [Ca2+] in plasma. Most common causes of this condition include: hyperparathyroidism, sarcoidosis, myelomatomas, reticuloses and leukaemias, carcinoma with bone metastases and overdosage with vitamin D.

Symptoms that are associated with hypercalcaemia include weakness and lethargy, nausea, vomiting, anorexia, constipation, polyuria and thirst, hypercalciuria and amenorrhoea. Not all the symptoms have to be present at the same time.  Over long periods of time condition can cause severe cardiovascular and renal damage (including calcification of soft tissues). Kidney stones are common phenomenon associated with hypercalcaemia. Also metabolic alkalosis may occur.

 

Hypocalcaemia

Condition described as abnormally low plasma [Ca2+]. This can be caused by: hypoparathyroidism, vitamin D deficiency, malabsorption, renal failure and alkalosis. Hypocalcaemia sets off increased parathyroid activity, unless it is caused by hypoparathyroidism. Neurological symptoms are described in tetany condition. Some mental features may appear, like nervousness, listlessness etc. Moreover ectodermal features appear, those include thinning of hair, brittle nails, dry skin and eczematous rashes and cataract.

 

Tetany

Decreased Tetany with Chvostek's signlevels of [Ca2+] can cause tetany, which is characterized as neurological disorder. Sensory effects, occuring when sensory neurons are affected, may involve “pins and needles” in extremities. Motor effects with motor nerves affected, can cause involuntary muscles contractions of hands, chest, abdomen, spine and legs. Spasms can be painful and last over log periods of time in severe cases. If respiratory muscles are affected, ischaemic effects can take place.

Image courtesy of: http://www.flickr.com/photos/14309782@N04/1607015823/

 

Hyperparathyroidism

Two forms of hyperparathyroidism are recognized: primary and secondary.

Primary hyperparathyroidism can be caused by adenomas, carcinomas or hyperplasia. Tumourous glands produce elevated amounts of PTH and do not respond to outside stimuli. This may be caused by gain-of-function mutation (e.g. synthesizing machinery) or loss-of-function mutation (e.g. CaSR). It causes hypercalaemia, kidney disease (renal stones) and bone disease (can cause bone pain, pathological fractures and clubbing of fingers). Bones are rarely affected by hyperparathyroidism, most probably due to efficiency of osteoblastic cells.

Secondary hyperparathyroidism is caused by long-lasting stimulation of parathyroid gland to produce PTH, as in chronic hypocalcaemia which may result from chronic kidney failure. It can progress intro tertiary hyperparathyroidism in which parathyroid gland continuously produces PTH.

 

Hypoparathyroidism

Three classes of this condition are recognized: after thyroidectomy, idiopathic and pseudohypoparathyroidism. Thyroidectomy results in low plasma [Ca2+] and raised plasma [P], which is similar in symptoms and results to hypocalaemia. Idiopathic hypoparathyroidism is caused by atrophy of all parathyroid glands due to unknown cause. Is very similar to thyroidectomy. Pseudohypoparathyroidism is similar in symptoms to idiopathic hypoparathyroidism, however it is caused by inability of peripheral tissue to respond to PTH. There are multiple possible causes of such condition. 

 

Familial Hypocalciuric Hypercalcemia

The Ca2+ receptor on cells of parathyroid gland is mutated, preventing decrease in signalling tone even when placma calcium level is extremly high. This is an autodsomal dominant disorder, with only one allele for CaSR present. In case of heterozygous disorder, normal and mutated receptors are expressed, while in homozygous disorder, both copies are defective. In case of homozygosis, severe hypercalcemia and hyperthyroidism are present and are life-threatening. Heterozygous patients do not show any symptoms of hypercalcemia.

 

Osteoporosis

Described as reduction of total bone mass with equal percentage Osteoporosisloss of every single component. This condition is associated with aging, commonly having an onset in post-menopausal stage in women and senile stage in men. The most common cause of the condition is declining levels of estrogens in women (condition affects women much more often than men), hyperparathyroidism, hyperthyroidism and Cushing disease. Prevention and treatment of the disease involves administration of antiresorptive drugs and pharmaceuticals that stimulate bone formation. Estrogen is most commonly used in this purpose, but calcitonin also finds its uses in therapy of osteoporosis. Intake of large doses of active form vitamin D is highly effective and safe for organism.

The following link will take you to short movie on osteoporosis:

http://www.healthination.com/content/view/video_popup/793/(partner_id)/1048

 Image courtesy of: http://www.flickr.com/photos/14309782@N04/1607015823/

 

Other diseases:

Fanconi’s syndrome – syndrome of multiple defects in renal reabsorption leading to excessive excretion of various substances.

 

Renal tubular acidosis – inherited, characterized by inability of kidney to excrete H+ leading to acidosis, followed by rickets and osteomalacia.

 

Renal calculi – commonly known as renal stones, have many varying causes.

 

Paget disease – disease that affects localized regions of skeleton. Characterized by rapid bone resorption and reactive sclerosis. High bone turnover is common. Can cause pain, deformity and fractures. Cause of disease remains unknown.

 


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Wojciech Stec