Dictionary

heterochromia iridis, sectoral A difference in color within an iris. A person with both brown and blue in the same eye has sectoral heterochromia iridis.

heterokaryon A cell with two separate nuclei formed by the experimental fusion of two genetically different cells. For example, heterokaryons composed of nuclei from Hurler syndrome and Hunter syndrome, both diseases of mucopolysaccharide metabolism, have normal mucopolysaccharide metabolism. This proves that the two syndromes affect different proteins and so can correct each other in the…

heteromorphism Something that is different in form. Chromosome heteromorphisms are normal variations in the appearance of chromosomes.

heteroploid A different chromosome number than the normal number of chromosomes. Abnormal numbers of chromosomes are associated with a number of disorders. For example, Down syndrome is the result of having three instead of two chromosome 21s.

heterosexual 1 A person who is sexually attracted to persons of the opposite sex. Colloquially known as straight. 2 The act or habit of oppositesex attraction.

heterosexuality Sexuality directed toward someone of the opposite sex.

hepatocellular carcinoma A cancer arising from the liver cells (hepatocytes). Liver damage, manifested by cirrhosis (scarring), is a primary risk factor for liver cancer. Cirrhosis may be caused by viral hepatitis, primarily hepatitis B and C, alcohol abuse, hemochromatosis, certain autoimmune diseases of the liver, and other diseases that result in chronic inflammation of the…

hepatomegaly An abnormally enlarged liver. Hepatomegaly can be caused by heart failure, blockage of blood vessels from the liver, or be a sign of chronic liver disease.

hepatosplenomegaly Abnormal enlargement of the liver and spleen. Hepatosplenomegaly is typically associated with chronic liver diseases.

hepatotoxic Being injurious to the liver. For example, alcoholic beverages and acetaminophen (brand name: Tylenol) can be hepatotoxic.

HER2 1 Human epidermal growth factor receptor. 2 A protein involved in normal cell growth that is found in abnormally high levels on, and promotes the growth of, some cancer cells, notably breast cancer cells. HER2-positive breast cancers tend to be more aggressive than other types of breast cancer and are less responsive to treatment…

herbal remedy A medication prepared from plants, including most of the world’s traditional remedies for disease. Most people think of herbal remedies as products sold over the counter as “supplements,” such as saw palmetto extract and goldenseal ointment. However, many over-the-counter and prescription drugs, including aspirin and digoxin, are based on ingredients originally derived from…