Dictionary

hyperphenylalaninemia Elevated levels of the amino acid phenylalanine in the blood. See also phenylalanine; phenylalanine hydroxylase deficiency; PKU; PKU, maternal.

hyperostosis Overgrowth of bone.

hyperopia See farsightedness.

hypernatremia Elevated sodium in the blood. Hypernatremia can be caused by medications or conditions such as dehydration or kidney disease. See also sodium.

hypermobility syndrome A condition in which joints can move beyond the normal range of motion predisposing them to injury and pain. Symptoms of hypermobility syndrome can include pains in knees, fingers, hips, and elbows, and the affected joints may sprain or dislocate. Joint hypermobility can disappear with aging from childhood to adulthood. Some persons have…

hypermagnesemia Excess magnesium in the blood. Kidney disease is one of the main causes of hypermagnesemia. Persons with impaired kidney function should be especially careful about their magnesium intake because they can accumulate magnesium, which is dangerous and sometimes fatal.

hyperlipidemia Elevated lipid (fat) levels in the blood. Hyperlipidemia can be inherited and increases the risk of disease of the blood vessels leading to stroke and heart disease.

hyperkeratosis Thickening of the outer layer of skin, which is composed of the protein keratin. Causes include normal wear and tear, inflammation of the skin, or genetic conditions.

hyperkalemia Elevated potassium in the blood. Hyperkalemia can be caused by taking excessive amounts of potassium, by medications, tissue trauma, and by diseases such as kidney failure. Hyperkalemia may not produce any symptoms, but severe hyperkalemia can lead to potentially fatal arrythmias of the heart.

hyperhidrosis A condition characterized by extreme and excessive sweating. Primary hyperhidrosis affects the hands, feet, and armpits and often has no identifiable cause. If the sweating occurs as a result of another medical condition, it is called secondary hyperhidrosis. In secondary hyperhidrosis, the sweating may be all over the body or may be localized to…

hyperglycemia Elevated blood glucose (sugar). Hyperglycemia is often found in diabetes mellitus. See also diabetes mellitus.

hyperexplexia A rare genetic disorder inherited in an autosomal dominant manner in which babies have an exaggerated startle reflex. Symptoms at birth may include muscle stiffness (hypertonia), an exaggerated response to being startled, and strong brain stem reflexes (especially head-retraction reflex). The startle reflex is sometimes accompanied by sudden stiffness (acute generalized hypertonia), which can…