Glossary

HDL
The smallest of the lipoproteins and are also the densest, due to their high proportion of protein. High concentrations of HDL (over 60 mg/dL) are said to help protect against cardiovascular disease.
Hemoglobin
Protein molecule in red blood cells that carries oxygen from the lungs to bodily tissues and carbon dioxide from tissues to the lungs.
Homeostasis
Resistance to change. How the body maintains its internal equilibrium to insure proper functioning.
Homocysteine
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.
Hormone
Chemical messenger from one cell, or group of cells, to another.
HPLC
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.
Hydrolysis
Breakdown of organic materials due to reaction with water.
Hypercalcaemia
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.
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).
Hypothalamus
Region at the base of the third ventricle in the brain that controls an immense number of bodily functions.