Parathyroid gland hypoparathyroidism

A form of hypoparathyroidism (hypofimction of the parathyroid glands) caused by the presence of activating mutations in the CaR, usually in the heterozygous state. 

Families affected by ADH, autosomal dominant hypoparathyroidism, and hypocal-cemic hypercalcinria have each been defined by gain-of-function mutations in the CASR gene (44). ADH is associated with the expression of constitutively activated CASR, which serves to suppress PTH secretion from the parathyroid gland. In the kidney it induces hypercalciuria, which further contributes to the hypocalcemia. 

The active forms of the D vitamins are la,25-dihydroxy-vitamin Dj and 25-hydroxy-vitamin Dj. They are formed by enzymatic hydroxylation in the liver microsomes and then in the kidney mitochondria by a ferredoxin flavoprotein and cytochrome P-450. The 1,25-dihydroxy vitamin is then transported to the bone, intestine, and other target organs (kidneys, parathyroid gland). Consequently, it can be considered a hormone since it is produced in one organ but used elsewhere. It mobilizes calcium and phosphate and also influences the absorption of these ions in the intestine, thus promoting bone mineralization. The hormone is also active in relieving hypoparathyroidism and postmenopausal osteoporosis, which, for example, results in the brittle bones of elderly women. 

Q10 Hypoparathyroidism is a rare condition which could develop following a decrease or deficiency of PTH secretion, or be due to reduction in the effectiveness of PTH on target cells. Deficiency of PTH may follow damage to the parathyroid glands during thyroid surgery. Deficiency of PTH decreases the concentration of plasma calcium and increases phosphate concentration. A metabolic crisis can occur when hypocalcaemia coincides with hypoparathyroidism. 

Q13 Magnesium is a major intracellular cation which acts as a co-factor in many intracellular enzyme reactions. Plasma concentration is normally 2 mg dl-1. This ion is abundant in the diet, and hypomagnesaemia is relatively uncommon, unless there is malabsorption or excessive loss via the kidney. However, when present, hypomagnesaemia can lead to hypoparathyroidism. Adjustment to the levels of magnesium can shift the function of the parathyroid glands back to normal. Chronic alcoholism, malnutrition, malabsorption, renal tubular dysfunction and excessive use of diuretics, such as loop and thiazide diuretics, may lead to hypomagnesaemia. Symptoms of magnesium deficiency include depression, confusion, muscle weakness and sometimes convulsions. 

Other causes of low serum calcium are less common. Hypoparathyroidism is due most commonly to parathyroid gland destruction during neck surgery (90%), and less commonly is idiopathic. Pseudohypoparathyroidism is biochemically similar to hypoparathyroidism however, these patients have inherited resistance to PTH and elevated concentrations of PTH. The molecular basis for the most common form, pseudohypoparathyroidism type I (Albright s hereditary osteodystrophy), is a reduction in guanine nucleotide regulatory complex. Ns, in the adenylate cyclase complex. 

Gain-of-fiinction mutations in the CASR gene have been identified in several families previously diagnosed with autosomal dominant hypocalcemia (ADH), autosomal dominant hypoparathyroidism, and hypocalcemic hypercalciuria [55], In the parathyroid gland, the activated CASR suppresses PTH secretion and in the kidney, it... 

Magnesium innuenees the secretion of PTH by the parathyroid glands, and severe hypomagncsacmia may cause hypoparathyroidism. 

The parathyroid glands secrete parathyroid hormone (PTH) that regulate calcium levels in the blood. A decrease in serum calcium stimulates the release of PTH. A decrease of PTH is called hypoparathyroidism and an increase in PTH is hyperparathyroidism. 

Calcitriol is used to treat hypoparathyroidism, but it does not stimulate excretion of calcium from the parathyroid gland. 

Primary hypoparathyroidism can be due to atrophy of the parathyroid gland, possibly by an autoimmune process. Another cause is removal of the glands during thyroidectomy. Primary hypothyroidism can result in hypocalcaemia with its associated clinical symptoms. 

The parathyroids are the smallest endocrine organs known in the animal body, and are represented by four structures situated at the back of the thyroid gland. Before their existence was recognised, they were removed with the thyroid tissue during experimental thyroidectomy, and the effects of the operation included both hypothyroid and hypoparathyroid phenomena. 

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