Vitamin D Council Glossary

A1c

Glycosylated hemoglobin that is usually elevated (6.5%–7.0% or higher) in people with diabetes mellitus. Normal range is 4%–5.9%.

Actin

The most abundant protein in eukaryotic cells. Actin is released into circulation by dying cells.

Adaptive immune system

System found only in jawed vertebrates which provides a pathogen- and antigen-specific response. The cells of the adaptive immune system are called lymphocytes, of which T-cells and B-cells are the major types.

Adenoma

Benign tumor of a glandular origin which typically originates from an epithelial cell.

Adequate Intake (AI)

Amount of a nutrient that appears to support good health. The label Adequate Intake (AI) is used when the RDA of a particular nutrient cannot be determined due to lack of information about that nutrient.

Adjuvant

Pharmacological or immunological agent that modifies the effect of other agents, such as drugs or vaccines, while having few, if any, direct effects when given by itself.

Agonist

A drug that binds to a specific receptor on a cell and triggers a response in the cell by imitating the action of the natural hormone that binds to that same receptor.

Albumin

Albumin is a protein that is made by the liver and is essential for maintaining the proper distribution of body fluids between intravascular compartments and body tissues.

Allele

An alternative form of a gene that can occupy a particular place on a chromosome.

Alphacalcidiol (1α-hydroxyvitamin D3,1α(OH)D3)

Synthetic analog of calcitriol. Used in the treatment of hypocalcemia, hypophosphatemia, rickets, and osteodystrophy associated with various medical conditions.

Amino acid

One of the 20 building blocks of protein.

Anabolic process

Metabolic process that uses cellular energy (what is an endergonic reaction) to build larger molecules from smaller ones. Protein synthesis is an example of an anabolic process.

Angiogenesis

Physiological process involving the growth of new blood vessels from pre-existing vessels. This process is normal during growth and development as well as wound healing, yet is also involved in the transition of tumors from dormancy to malignancy.

Anterior pituitary

The anterior lobe of the pituitary gland and part of the endocrine system. Regulates several physiological processes including stress, growth, and reproduction through the production and secretion of peptide hormones.

Anthracosis

Noncollagenous and less-inflammatory pneumoconiosis caused from inhaling carbon or coal dust.

Antiangiogenic

Anything which blocks, or helps to reduce, the formation of new blood vessels. Relatively new in cancer treatment strategy, antiangiogenetic drugs bear fewer side effects and are less-risky than treatments such as chemotherapy.

Antibody (Antibodies)

Protein on the surface of B-cells that is secreted into the blood (or lymph) in response to the presence of an antigen in order to bind to, and neutralize, the antigen.

Antigen

Any substance (such as a chemical, bacterium, virus, or pollen) that causes your immune system to produce antibodies against it.

Antimicrobial

Substance that kills or inhibits the growth of microbes such as bacteria, fungi, or viruses.

Antimicrobial Peptide (AMP)

Small protein with broad-spectrum antimicrobial activity against bacteria, viruses, and fungi. Antimicrobial Peptides (AMPs) alter the host immune response through receptor-dependent interactions and have been shown to be important in such diverse functions as angiogenesis, wound healing, and chemotaxis.

Antioxidant

Compound synthesized in the body, or obtained from diet, which helps prevent the formation of, and removes, reactive oxygen species.

Apoptosis

One of the main types of programmed (normal) cell death.

Astrocyte

Star-shaped glial cells in the brain and spinal cord that perform many functions, including biochemical support of endothelial cells, provision of nutrients to nervous tissue, and playing a principal role in the repair and scarring process of the brain and spinal cord following traumatic injuries.

Astrocytoma

Cancer of the brain that originates in brain cells called astrocytes.

Asymptomatic

Neither causing, nor exhibiting, symptoms of disease.

Atherosclerosis

Commonly referred to as "hardening of the arteries," atheroscleros is a chronic inflammation of the arterial blood vessel walls due to the formation of plaques.

Athymic mice

Laboratory mice lacking a thymus gland. Athymic mice have no T-cells and therefore are useful in research because they do not reject tumor, or other, cells transplanted from mice, humans, or other species.

Autocrine function (Autocrine signaling)

A cell signaling itself through a chemical that it first synthesizes and then responds to. Autocrine signaling occurs either within the cell's cytoplasm or by the cell's secretion of the chemical, which then interacts with receptors on the cell's surface.

Autonomic Nervous System (ANS)

The part of the Peripheral Nervous System consisting of motor neurons that control internal organs such as muscles in the heart and smooth muscle in the intestine, bladder, and uterus. The Autonomic Nervous System consists of two subsystems: the Sympathetic Nervous System (involved in "fight or flight" response) and Parasympathetic Nervous System (involved in relaxation).

Axon

An extension of a neuron cell body that transports information away from the cell body, usually by an electrical impulse.