Ergocalciferol

Ergocalciferol, or vitamin D₂, is a fat-soluble vitamin produced when ultraviolet light converts ergosterol. It helps regulate calcium and phosphate balance and is used to prevent or treat deficiency.

Ergosterol: A sterol found in fungi and yeast that ultraviolet light can convert into ergocalciferol. Ultraviolet irradiation of this precursor produces ergocalciferol.
Vitamin D deficiency: A state in which vitamin D availability is inadequate to support normal calcium and bone metabolism. Preventing or treating this deficiency is the primary clinical purpose of ergocalciferol.
Vitamin D: A group of fat-soluble secosteroids that support calcium and phosphate regulation and bone health. Ergocalciferol is one member of this broader vitamin group.
Vitamin D₃: The common name for cholecalciferol, a form of vitamin D produced in skin and found in some foods. Vitamin D₃ is the main alternative to ergocalciferol in supplements and treatment.
Cholecalciferol: Vitamin D₃, formed in skin from 7-dehydrocholesterol and also obtained from foods and supplements. It is the closely related vitamin D form often compared with ergocalciferol.
Rickets: A childhood disorder of growing bone mineralization, commonly caused by vitamin D or calcium deficiency. Ergocalciferol can prevent or treat nutritional rickets caused by vitamin D deficiency.
Secosteroid: A steroid-like molecule with one of the four rings of the steroid framework broken. The broken-ring structure distinguishes vitamin D compounds, including ergocalciferol.
Alfacalcidol: A vitamin D analogue converted in the liver to the active hormone calcitriol. Unlike ergocalciferol, it bypasses the kidney's activation step.
Calcifediol: The circulating form of vitamin D produced when the liver hydroxylates vitamin D₂ or D₃. The liver converts ergocalciferol into this major blood metabolite.
Osteomalacia: Impaired mineralization of mature bone, often associated with vitamin D deficiency. Vitamin D₂ treatment may address deficiency underlying this bone disorder.

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Adolf WindausBroader topic: Windaus’s investigations connected irradiated ergosterol with this vitamin.