Vitamin D Council Glossary

Iatrogenic

Induced inadvertently by a physician, surgeon, medical treatment, or diagnostic procedure.

Idiopathic

Of unknown cause or origin.

IL-12/IFNgamma

Neuroendocrine-immune system axis that is crucial for protective immunity to mycobacterium in humans and mice.

Immune system

Collection of mechanisms within an organism that protects against infection by identifying and killing pathogens and tumor cells. See innate immune system and adaptive immune system.

Immunomodulatory

Having the ability to alter or regulate one or more immune functions.

Immunosuppressive

Inhibits or prevents activity of the immune system. Immunosuppressive substances are used in the treatment of autoimmune diseases, some inflammatory diseases, and for preventing transplant organ rejection.

Innate immune system

Cells and mechanisms found in all classes of plant and animal life which provide immediate defense against infection in a non-specific manner.

Institute of Medicine (IOM)

Component of the United States' National Academy of Sciences whose mission is to "serve as adviser to the nation to improve health."

Insulin

Hormone that is secreted by groups of cells within the pancreas (called islet cells) in response to a detected increase in blood sugar.

International Unit (IU)

A unit of measurement for the amount of a substance that is based on measured biological activity. For vitamin D, one IU is equal to 0.025 micrograms (µg).

Intron

DNA region in a gene that is not translated into protein.

Ischemia (Ischaemia)

Restriction in blood supply that results in damage to, or dysfunction of, tissue.

Isoform

Different form of a protein that may be produced from different genes or from the same gene by alternative splicing.

Isomer

Molecule with the same chemical formula, but different arrangement of atoms, as another.