Physiology of vitamin D
  
Form of vitamin D
There are three forms of the vitamin and to understand the endocrine processes in the body, to distinguish them and to have some idea about them.
Cholecalciferol This vitamin D3, its, so to speak, the natural form. It is formed in the skin itself under the action of sunlight. It can also be downloaded as a food additive.
Calcidiol This form is a derivative of vitamin D3 and is located in the blood. Is a hormone. To diagnose a lack of vitamin D blood test shall, where the number of detected calcidiol in the blood. When it comes to lack of vitamin D in the blood, then we have in mind calcidiol. Your doctor will check the required level of calcidiol. 
Calcitriol This form - derived from the preceding species in the vitamin. It is formed in the kidneys and is also a hormone. This is the most powerful hormone. It is a good opponent cancer. Sometimes it is called the active form of vitamin D3. Quantitative levels of calcitriol should in no case be used to diagnose vitamin D deficiency in the body.

Endocrinology of vitamin D
Cholecalciferol forms in the skin Cholecalciferol itself appears in the skin by ultraviolet UVB, when they get on uncovered skin clothing. Very large, abnormal dosage Cholecalciferol appear when the irradiation is particularly intense, that is during the warm season, when the body is open as, of course, if you are not protected by glass or special tools. After irradiation, the skin turns pink, but not a red color. Scientists have found that the skin of a man standing in the open sun in a bathing suit in the skin is formed of up to 50 thousand units of Cholecalciferol. In addition it was found that on average, so the person gets 20 thousand units of vitamin D, which exceeds the daily rate of 100 times. This is very important.
The skin also has another remarkable property - it does not poison the body to vitamin excess worked out. Creating 20,000 units of vitamin, the skin begins to break down. And the more it produces it, the more gets rid of the excess. So there was found no case where a person has received vitamin deficiencies of vitamin D from sunlight, while intoxication known to them as a result of oral administration.

The form of Cholecalciferol in animal skins animals and birds also produce Cholecalciferol, but not in the skin, and skin or feathers. so as to skin the sunlight can not reach. An interesting fact is that animals receive vitamin D, licking the skin. that is taken orally. So that taking vitamin D in the form of medicine we do not do anything unnatural.
Developing Calcidiol in the liver Once vitamin D3 is obtained by oral administration or as a result of its synthesis in the sun, it falls into the liver, where it is transformed into Calcidiol. To date, this form of vitamin D is considered as hormone-steroid. What we know for sure that it supports the normal calcium. But the main thing here is the form in which the vitamin is stored in the body. Calcidiol a supply of vitamin. When is the lack of it, that is, the level drops below Calcidiol 40 ng / ml is necessary to replenish stocks. In order to assess the need to maintain such a reserve is normal, you need to understand one of the stages in metabolism. After the conversion of vitamin D3 in Calcidiol there are two scenarios: first, more important, as is necessary for the body, the second - it's part in the processes in cells. With a deficit Calcidiol, the body starts to use it only in the first form.

The development of the kidney Calcitrio End of the first path in the kidney. There are transformed into vitamin Calcitriol. This is a very powerful hormone, the most powerful of them all, which are produced by the human body. The challenge for the steroid hormones - is shut down or, conversely, to include a particular gene. They are always needed and they must be very careful, because sometimes their excessive activity. Calcitriol, created in the kidneys, passes into the blood and maintains the desired level of calcium. Calcium is necessary for the body to the bones, all cells in general. Therefore, the deficit Calcitriol calcium level drops, which leads to disease. The main objective of Calcidiol - is to get to the kidney and transformed into Calcitriol, and in the right quantity, to further support the calcium in the blood at the proper level.

Calcitriol largely produced in the tissues The second scenario is vitamin D in the tissue, where the main thing is happening. Everything interesting about vitamin D, which was opened in the last decade, it belongs to the second option. If the reserve is full of Calcitriol, calcium is maintained in the right quantity, Calcidiol moves the other way, which leads him directly into the cells. To date, this way is studied in full and provides answers to many of the scientists and medical issues, particularly with respect to cancer. This problem intracellular and extracellular vitamin D. They are important for understanding of the reason why supply of vitamin D in the blood should always be normal, otherwise completely Calcidiol will be spent to support the kidneys of calcium at the right level, and the cells will not get anything.
Calcitriol, produced in the tissues, protects against cancer While the supply of vitamin D is full, Calcidiol sent to the cell, where a Calcitriol, not giving to develop cancer. Speaking on the fact that cells can create as many Calcitriol, how will Calcidiol. This is not limited. Formulation of Calcitriol so interesting by the fact that unlimited production does not occur anywhere else in the body. This is the second important point about vitamin D. Other hormones indefinitely so do not form, they inhibit their own creation. For example, the reaction of chemicals made from cholesterol progesterone, when the latter is accumulated in the right quantity, it inhibits the corresponding reactions. This is typical of the production of other hormones in the body, so the body can constantly maintain hormonal balance. The mechanism of inhibition is not only present in the formulation of Calcitriol in the tissues. Even when the required number is obtained, the development will not stop.

  This is important because such a mechanism is very different from the normal state of affairs. In today's world people live a lifetime with low calcidiol in the blood, and hence a small amount of Calcitriol in the tissues. A Calcitriol, the most powerful hormone in the human body, on and off genes in different ways, in their turn produce proteins that fight cancer, or conversely, that it provoked. Built-in Protection What then prevents the excess Calcitriol in the cells? Something is still needs to stop this process is not infinite as it. The answer to this question - distribution. The greater the number of Calcitriol appears, the more volume it goes in the bile. But this is not the main thing. Need a little Unwind event back. One option to reduce Calcitriol in the tissues, it is necessary to reduce the level of calcidiol in the blood. Perhaps there is a special reaction that prevents the transformation of calcidiol in the liver? No, it's not. In the normal state of the body than the vitamin D produced in the skin, the more calcidiol appears in the blood. Here is the answer! Leather! Here it is protection, which limits the reception of 20 thousand units. This is suntan. Tanning makes the skin less sensitive to ultraviolet rays, and hence the amount of vitamin D produced a smaller, only 10 thousand units. So by natural defenses. Therefore, the responsibility lies with the person who is in full sun or drink vitamin D in addition.
No sun - no vitamin D Previously, many millions of years ago our ancestors were always in the sun without any clothes. And only 50 thousand years ago they moved to other places with lower activity of the sun. Then he invented the clothes, houses, cities, depriving themselves of the sun light more and more. Riding in a car instead of walking, antisolar film on the glass, and now the sun cosmetics. So the person alone decreases in their body's natural defenses against cancer.
Reducing time spent in open sunlight, led to the fact that the major diseases of our century have diabetes, cancer and so on. Think about it.