Ergokalciferol

Ergokalciferol, also known as ergocalciferol, is a form of vitamin D (vitamin D2). It is a fat-soluble secosteroid that acts as a prohormone involved in calcium and phosphate metabolism.

In nature, ergocalciferol is found in fungi, yeast, and some mushrooms; industrially it is produced by ultraviolet irradiation of ergosterol. It is not typically present in animal-derived foods.

After ingestion, ergocalciferol is absorbed with dietary fats and transported to the liver, where it is hydroxylated to 25-hydroxyergocalciferol. It is then further hydroxylated in the kidney to 1,25-dihydroxyergocalciferol, the active hormone that binds the vitamin D receptor and promotes intestinal absorption of calcium and phosphate, supporting bone health.

Vitamin D2 is generally less potent at raising and maintaining serum 25-hydroxyvitamin D levels than vitamin D3 (cholecalciferol); efficacy depends on the dose and formulation used.

Ergokalciferol is used to prevent and treat vitamin D deficiency and diseases such as rickets and osteomalacia. It is also employed as a supplement for individuals who avoid animal products or have limited sun exposure and may be used to fortify certain foods, including some mushrooms.

High-dose regimens require medical supervision; excessive intake may cause hypercalcemia and related complications, including soft tissue calcification and kidney stones. It can interact with various medications and conditions, so monitoring is advised for long-term or high-dose use.

Ergocalciferol is available as an over-the-counter dietary supplement and in some prescription formulations in many countries. Dosage units are expressed in micrograms or international units, with 1 μg of ergocalciferol equaling 40 IU.