Vitamin D is a fat-soluble vitamin that exists in the form of Vitamin D3 and Vitamin D2. A vitamin D3 is synthesized in the skin of animals by the reaction of light molecules with 7-dehydrocholesterol which is a cholesterol metabolite. Vitamin D2 comes from plants, yeast, and fungi. There are dietary sources of Vitamin D such as mushrooms, liver, eggs, and fish cod liver oil.
Vitamin D3 and D2 are biologically inactive forms of Vitamin D. Both forms undergo hydroxylation reactions in the liver and kidneys to transform into 1,25-OH-Cholecalciferol.
What is the difference that makes vitamin D and calcitriol different?
Calcitriol is the active form of Vitamin D. It is 1000 times more potent than Vitamin D2 and D3 in terms of binding to the Vitamin D receptors. Vitamin D2 and D3 have no significant biological activity and become useful for the body only when synthesized to Calcitriol.
Calcitriol plays a major role in calcium and phosphorus metabolism to maintain bone health. Low levels of plasma calcium lead to bone diseases. Calcitriol maintains normal plasma calcium levels by increasing the absorption of calcium and phosphate in the gastrointestinal tract, promoting tubular absorption of calcium in the renal system, and releasing calcium stores from the bones.
Calcitriol also acts directly on the parathyroid gland. It regulates the levels of calcium receptors and inhibits the transcription of parathyroid encoding genes. The parathyroid is the hormone that increases the levels of calcium in the blood.
Uses of Calcitriol
Low levels of calcium and phosphate in the blood due to kidney failure or thyroid gland problems cannot be treated by the administration of vitamins D2 and D3. This is because both these forms of Vitamin D are not biologically active. Thus, Calcitriol must be given to the person to raise his/her plasma calcium levels.
In the case of chronic renal failure, the kidneys cannot synthesize a sufficient amount of Calcitriol. This leads to abnormally low levels of plasma calcium and phosphate. Oral administration of calcitriol makes up for its low renal production and restores the calcium and phosphate levels to normal.
Calcitriol can also be given to people suffering from Hypoparathyroidism. Hypoparathyroidism is a condition in which the thyroid glands do not produce enough parathyroid hormone. Parathyroid hormone stimulates the production of calcitriol in the kidneys by increasing the synthesis of 1- alpha-hydroxylase enzyme. Insufficient parathyroid hormone leads to low production of calcitriol and a consequent decrease in plasma calcium levels. Oral administration of calcitriol compensates for the low renal calcitriol production and restores the calcium levels to normal.
How to buy calcitriol?
There are many Calcitriol exporters shipping calcitriol formulations all over the world. Calcitriol capsules or oral solutions or injectable solutions can be purchased over the counter or through online pharmacies. A doctor’s prescription is required to purchase calcitriol. Many reputed online pharmacies also offer doctor consultations virtually.
Calcitriol exporters use the brand names Calcijex andRocaltrol for selling calcitriol.
Oral liquid-filled calcitriol capsules come in doses of 0.25 and 0.5 mcg. Oral solutions are available in 1 mcg/ml concentration. Injectable solutions come in 1 and 2 mcg/ml concentrations.
The initial adult dose for patients suffering from renal failure is 0.25 mcg daily which can increase by 0.25 mcg daily after every 4-8 weeks. For patients suffering from hypoparathyroidism, the daily recommended dose is 0.25-2 mcg.
Hypercalcemia is a major side effect of taking calcitriol. Symptoms such as fever, stomach pain, constipation, dehydration, increased urination, and thirst might indicate high levels of calcium in the blood, necessitating medical help.
Other side effects include weight loss, low appetite, weakness, drowsiness, and urinary tract infection.