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Sunday, November 24, 2019

Vitamin D deficiency

            Vitamin D deficiency





Vitamin D deficiency






A deficiency of vitamin D makes it difficult for the body to maintain enough calcium in the bloodstream. When there are insufficient levels of vitamin D, the production of a protein that promotes the absorption of calcium by the cells that line the intestine decreases. This allows calcium to pass through the intestine without being absorbed. The parathyroid glands detect low calcium levels in the blood and secrete more parathyroid hormone. Rising parathyroid hormone levels cause calcium to be released from the bones and retained in the kidneys

Calcium and magnesium deficiencies often accompany vitamin D deficiency and are associated with convulsions in infants and degenerative neurological disorders such as Parkinson's disease and Alzheimer's disease in adults


Deficiency symptoms of vitamin D


Long-term deficiency leads to low levels of calcium in the blood (hypocalcaemia) and phosphate (hypophosphataemia), resulting in softening of the bones. In children, this causes abnormal bone development (rickets) and, in adults, osteomalacia, which causes back pain, muscle weakness, bone pain and fractures


You may be deficient in vitamin D if:


• You are an older adult. You are now producing only half of the vitamin D in your skin compared to when you were younger

• Does not receive sunlight. People who are confined to their homes or who live in nursing homes are particularly at risk

• have kidney or liver disease. It is not possible to convert vitamin D3 into its most active forms. Talk to your doctor about supplements (Vitamin D supplements)

• Take medications such as cholestyramine (Cholybar or Questran) or colestipol (Colestid) to lower cholesterol. These drugs block the absorption of vitamin D and other fat-soluble substances vitamins Talk to your doctor about supplements

• Take corticosteroid drugs such as cortisone, prednisone or dexamethasone for allergies, asthma, arthritis or another health problem. These drugs can reduce the level of vitamin D3. Talk to your doctor about supplements

• Take anticonvulsant drugs such as phenytoin (Dilantin) or phenobarbital. These drugs interfere with the way you use vitamin D. Talk to your doctor about supplements

• You are strictly vegetarian or vegan. There is very little vitamin D in plant foods. If you don't drink milk and not going out much, you and your vegan kids may not be enough Vitamin D (Vitamin D Food Sources)

• Alcohol abuse. Alcohol blocks your ability to absorb vitamin D from the intestine and store it in the liver


Effects of vitamin D deficiency


The deficiency in turn causes stimulation of the parathyroid gland. The hormone secreted by the gland extracts calcium from the bones to bring calcium back to the blood to adequate levels. This process causes rickets in infants and children and osteomalacia in adults

At the beginning of the deficiency, there is a decrease in the efficiency of intestinal calcium absorption and a consequent decrease in the level of calcium in the plasma. In response to hypocalcaemia, the plasma concentration of Ca2 + is restored to normal, but the concentration of Pi decreases. The increase in Ca2 + concentration is mainly caused by two effects

First, PTH, acting with whatever 1α, 25 (OH) 2D is still present at the beginning of the deficiency, causes the mobilization of Ca2 + and Pi from the bone; second, PTH, acting alone, causes an increase in renal calcium reabsorption. The decrease in the plasma concentration of Pi is caused by a very strong effect of PTH on the kidney causing excessive excretion of phosphate, an effect that is generally large enough to negate the increased mobilization of phosphate from the bones

During a prolonged deficiency of vitamin D, an increased secretion of PTH necessary to maintain calcium homeostasis causes extreme osteoclastic reabsorption of the bones. This in turn causes a progressive weakening of the bone and imposes a marked physical stress on the bone, with consequent rapid osteoblastic activity. Osteoblasts deposit large quantities of osteoids, but due to insufficient Ca2 + and Pi, calcification does not occur. Therefore, the inability to calcify the newly formed bone matrix eventually leads to rickets or osteomalacia


Risk factors for deficiency


The most likely cause of vitamin D deficiency is inadequate exposure to sunlight. This can happen with people who don't go out much, those in areas of the world where pollution blocks ultraviolet (UV) light or where time forbids spending too much time outdoors. The glass filters out the rays necessary for the formation of vitamins, such as sunscreen. People with dark skin can also absorb small amounts of ultraviolet light needed to perform the vitamin conversion

Babies are usually born with a supply of vitamin for about nine months, but breast milk is a scarce source. People who are born prematurely have an increased risk of vitamin D and calcium deficiency and may be prone to tetany

People with some intestinal, liver, and kidney disease may not be able to convert vitamin D3 into active forms and may need an activated type of supplemental vitamin D

Those taking certain medications may require supplements, including anticonvulsants, corticosteroids or cholesterol-lowering drugs, cholestyramine or colestipol. This means that people taking arthritis, asthma, allergies, autoimmune conditions, high cholesterol, epilepsy or other seizure problems should consult a health care professional about the convenience of taking vitamin D. As with other vitamins, alcohol abuse also has a negative effect. In the case of vitamin D, the ability to absorb and store it is reduced by chronic abuse of alcoholic products

Populations with poor nutritional status may tend to have a low content of vitamin D and other vitamins. This can be an effect of poor sun exposure, poor intake or poor absorption. Other groups that may need above-average amounts of vitamin D include those who have recently undergone surgery, serious injury or burns. High levels of stress and chronic degenerative diseases also tend to increase the vitamin requirement


Dosage range for treating deficiency


In general, rickets caused by food shortages are initially treated with 3,000–6,000 IU of vitamin D per day, depending on the age of the child, followed by a maintenance dose of 400 IU

Osteomalacia caused by vitamin D deficiency is initially treated with 3,000-40,000 IU per day, followed by a daily maintenance dose of 400 IU

Deficiency caused by impaired intestinal absorption or liver disease is treated with 40,000 IU per day (adults) and 10,000-25,000 IU per day (children)


Hypocalcaemia due to hypoparathyroidism is treated with doses up to 100,000 IU. Simple deficiency is generally treated with 400 IU of oral supplements



Abbreviations


  • 1,25 (OH) 2D 1,25-dihydroxyvitamin D
  • 25 (OH) D 25-hydroxyvitamin D
  • International Unit IU
  • UV ultraviolet

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