Dictionary

double helix The structure of DNA, in which two strands of DNA spiral about each other.

double pneumonia See pneumonia, double.

double-blinded study A medical study in which both the subjects participating and the researchers are uaware of when the experimental medication or procedure has been given. Double-blinded studies are often used when initial studies shows particular promise.

double-jointed Popular term to describe a joint that is unusually flexible. Medically, the joint is said to be hyperflexible, hyperextensible, or hypermobile. People whose fingers are hypermobile have higher rates of arthritis in the hands. Marked joint hypermobility is a feature of Ehlers-Danlos syndrome. See also Ehlers-Danlos syndrome.

douche Usually, a stream of water applied into the vagina for cleansing purposes. A douche can use a solution, such as vinegar and water, rather than simple water, and it can be directed at any body cavity or part.

douching Using water or a medicated solution to clean the vagina and cervix or any other body cavity or part.

Douglas, pouch of See pouch of Douglas.

Dowager’s hump An abnormal outward curvature of the thoracic vertebrae of the upper back. Compression of the front portion of the involved vertebrae due to osteoporosis leads to forward bending of the spine (kyphosis) and creates a hump at the upper back. Like most osteoporotic changes, it is often preventable.

Down syndrome A common birth defect that is usually due to an extra chromosome 21 (trisomy 21). Down syndrome causes mental retardation, a characteristic facial appearance, and multiple malformations. It occurs most frequently in children born to mothers over age 35. It is associated with a major risk for heart problems, a lesser risk of…

downregulation Reduction in the number of receptors on the surface of target cells, making the cells less sensitive to a hormone or another agent.

dizziness, presyncopal Dizziness before fainting. Some symptoms of dizziness, such as “wooziness,” feeling as though one is about to black out, and tunnel vision may be presyncopal and are due to insufficient blood flow to the brain. These symptoms are typically worse when standing, improve with lying down, and may be experienced by healthy individuals…

DMD Duchenne muscular dystrophy. See muscular dystrophy, Duchenne.