Dictionary

hormone, androgenic Any hormone that promotes the development and maintenance of male sex characteristics. Testosterone is an androgenic hormone.

hormone A chemical substance produced in the body that controls and regulates the activity of certain cells or organs. Many hormones are secreted by special glands, such as thyroid hormone produced by the thyroid gland. Hormones are essential for every activity of life, including the processes of digestion, metabolism, growth, reproduction, and mood control. Many…

hookworm An intestinal parasite that infests a billion people, mainly in tropical and subtropical areas. Infection is from contact with soil contaminated by hookworm larvae. First signs are itching and rash at the site where the larvae penetrate the skin. This is followed by diarrhea, intestinal cramps, pain, anorexia, weight loss, and anemia. Loss of…

homosexuality Sexuality directed toward someone of the same sex.

homosexual 1 A person who is sexually attracted to persons of the same sex. Colloquially known as gay. 2 The act or habit of same-sex attraction.

homology Similarity in DNA or protein sequences between individuals or between species.

homologous chromosomes A pair of chromosomes that contain the same gene sequences, each derived from one parent.

homologous 1 Similar in appearance, form, or function. 2 Paired or matched; usually referring to the relationship between two chromosomes that are paired and so are homologs of each other.

homolog 1 One chromosome of a pair. 2 A gene from one species that has a common origin and functions the same as a gene from another species. Also spelled homologue.

homocystinuria A genetic disease that is due to an enzyme deficiency that permits a buildup of the amino acid homocysteine. Progressive mental retardation is common, but does not always occur, in untreated cases of homocystinuria. The finding of vascular disease and premature arteriosclerosis in persons with homocystinuria led to the theory that homocysteine may be…

homocysteine An amino acid that is produced by the human body, usually as a byproduct of consuming meat. Homocysteine is normally converted into other amino acids. An abnormal accumulation of homocysteine, which can be measured in the blood, can be a marker for the development of heart disease. Elevated levels of homocysteine in the blood…

homo- Prefix meaning same, as in homology (similarity in DNA or protein sequences between individuals or between species) and homosexual (a person who is sexually attracted to persons of the same sex). The opposite of homo- is hetero-.