insomnia The perception or complaint of inadequate or poor-quality sleep due to a number of factors, such as difficulty falling asleep, waking up frequently during the night with difficulty returning to sleep, waking up too early in the morning, or unrefreshing sleep. Insomnia is not defined by the number of hours of sleep a person…
insertion A chromosome abnormality that is due to insertion of a segment from one chromosome into another chromosome.
insemination The deposition of semen in the female reproductive tract. With sexual intercourse, the deposit is made within the vagina or the cervix. By artificial means, such as intrauterine insemination, the deposit can be made directly into the uterus.
insect sting A sting from a stinging insect, such as a bee, hornet, yellow jacket, or wasp, that can trigger allergic reactions. These reactions vary greatly in severity. Avoidance and prompt treatment are essential. In selected cases, allergy injection therapy is highly effective.
INR International normalized ratio.
inner ear See ear, inner.
injury, cold See cold injury.
inhibitor, protease See protease inhibitor.
inhibin One of two hormones (designated inhibin-A and inhibin-B) secreted by the gonads (by Sertoli cells in the male and the granulosa cells in the female) and that inhibit the production of follicle-stimulating hormone (FSH) by the pituitary gland. The inhibins are also involved in the control of the production of gametes and embryonic and…
inheritance, Y-linked Inheritance of genes on the Y chromosome. Because normally only males have Y chromosomes, Y-linked genes can be transmitted only from father to son. Also known as holandric inheritance.
inheritance, multifactorial A type of hereditary pattern seen when there is more than one genetic factor and, sometimes, environmental influence. Many common traits and many common diseases are multifactorial. Skin color, for example, is multifactorially determined, as is intelligence. Type 2 diabetes is multifactorial because it is due to inherited (genetic) factors but may also…
inheritance, mitochondrial The inheritance of a trait encoded in the mitochondrial genome. Mitochondrial inheritance does not obey the classic rules of genetics. Mitochondrial DNA is always inherited from the mother only, meaning that persons with a mitochondrial disease may be male or female but are always related in the maternal line, and no male with…