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Hyperparathyroidism is an increase in parathyroid hormone (PTH) levels in the blood. [1][4] This occurs from a disorder either within the parathyroid glands (primary hyperparathyroidism) or as response to external stimuli (secondary hyperparathyroidism). [1] Symptoms of hyperparathyroidism are caused by inappropriately normal or elevated blood ...
PTH is secreted primarily by the chief cells of the parathyroid glands. The gene for PTH is located on chromosome 11. It is a polypeptide containing 84 amino acids, which is a prohormone. It has a molecular mass around 9500 Da. [6] Its action is opposed by the hormone calcitonin. There are two types of PTH receptors.
A diet insufficient in vitamin D, combined with inadequate sunlight exposure, can lead to vitamin D deficiency, which is defined as a blood 25-hydroxyvitamin D or 25(OH)D level below 12 ng/mL (30 nmol/liter). Vitamin D insufficiency, on the other hand, is characterized by a blood 25(OH)D level between 12–20 ng/mL (30–50 nmol/liter).
Vitamin D deficiency is typically diagnosed by measuring the concentration of the 25-hydroxyvitamin D in the blood, which is the most accurate measure of stores of vitamin D in the body. [1][7][2] One nanogram per millilitre (1 ng/mL) is equivalent to 2.5 nanomoles per litre (2.5 nmol/L). Severe deficiency: <12 ng/mL = <30 nmol/L[2] Deficiency ...
Vitamin D toxicity. Cholecalciferol (shown above) and ergocalciferol are the two major forms of vitamin D. Specialty. Endocrinology, toxicology. Vitamin D toxicity, or hypervitaminosis D, is the toxic state of an excess of vitamin D. The normal range for blood concentration in adults is 20 to 50 nanograms per milliliter (ng/mL).
Thyroid and parathyroid. Secondary hyperparathyroidism is the medical condition of excessive secretion of parathyroid hormone (PTH) by the parathyroid glands in response to hypocalcemia (low blood calcium levels), with resultant hyperplasia of these glands. This disorder is primarily seen in patients with chronic kidney failure.
Calcifediol, also known as calcidiol, 25-hydroxycholecalciferol, or 25-hydroxyvitamin D3 (abbreviated 25 (OH)D3), [1] is a form of vitamin D produced in the liver by hydroxylation of vitamin D 3 (cholecalciferol) by the enzyme vitamin D 25-hydroxylase. [3][4][5] Calcifediol can be further hydroxylated by the enzyme 25 (OH)D-1α-hydroxylase ...
CYP2R1 is cytochrome P450 2R1, an enzyme which is the principal vitamin D 25-hydroxylase. [5] [6] In humans it is encoded by the CYP2R1 gene located on chromosome 11p15.2. [7]It is expressed in the endoplasmic reticulum in liver, where it performs the first step in the activation of vitamin D by catalyzing the formation of 25-hydroxyvitamin D. [8]