Vitamin D Council Glossary

# A B C D E F G H I J–K L M N O P R S T U V
A set of alleles of a group of closely linked genes which are usually inherited as a unit.
Method of treating illness by exposure to the rays of the sun (ultraviolet radiation).
Protein molecule in red blood cells that carries oxygen from the lungs to bodily tissues and carbon dioxide from tissues to the lungs.
High-Density Lipoprotein (HDL)
The smallest of the lipoproteins and also the densest, due to a high proportion of protein. High concentrations of HDL (over 60 mg/dL) are said to help protect against cardiovascular disease.
A major component of the brains of humans and other mammals.
Resistance to change. How the body maintains its internal equilibrium to insure proper functioning.
An amino acid in the blood. High plasma (blood) homocysteine has been shown to increase risk of coronary heart disease, stroke, and peripheral vascular disease.
Having identical alleles for a single trait.
Chemical messenger from one cell, or group of cells, to another.
High Performance Liquid Chromatography.
Humoral immune response
The aspect of immunity that is mediated by secreted antibodies, produced in the cells of the B lymphocyte.
Breakdown of organic materials due to reaction with water.
Hypercalcaemia (also spelled hypercalcemia)
An elevated calcium level in the blood that is often indicative of other diseases, especially hyperparathyroidism and malignancy. Normal range is 9–10.5 mg/dL (2.2–2.6 mmol/L). Hypercalcaemia can also occur due to an excessively high intake of vitamin D, however published cases typically involve an intake of more than 40,000 IU of vitamin D per day.
Primary hyperparathyroidism: Disorder of the parathyroid glands in which one or more become enlarged and secrete too much parathyroid hormone (PTH), causing excessive calcium in the blood. see hypercalcemia.
Secondary hyperparathyroidism: Excessive PTH secretion in response to hypocalcemia (low blood calcium levels) due to a pre-existing condition, usually chronic renal failure.
Hypervitaminosis A
Occurs when the maximum limit for liver stores of retinoids is exceeded, resulting in the excess vitamin A entering circulation and causing systemic toxicity. Most cases of vitamin A toxicity result from an excess intake of supplemental vitamin A in the form of retinol.
Hypervitaminosis D
Excessively high blood calcidiol level. One of the least toxic substances to humans, vitamin D3 overdose doesn't occur until more than 100 times the daily RDA has been taken daily for several months. Acute one-time overdoses require over 50 mg (ten thousand times the RDA).
Medical condition where serum levels of albumin are abnormally low.
Hypocalcaemia (also spelled hypocalcemia)
A type of electrolyte disturbance in which there are low levels of serum calcium in the blood.
Hypocalcaemic (also spelled hypocalcemic)
see hypocalcaemia.
Region at the base of the third ventricle in the brain that controls an immense number of bodily functions. One of the most important functions of the hypothalamus is to link the nervous system to the endocrine system via the pituitary gland.
Having deficient tone or tension, as in a "hypotonic muscle."
Hypovitaminosis D
Also known as vitamin D deficiency. Medical condition where a lack of vitamin D puts one at risk for diseases associated with vitamin D deficiency.

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