Adrenal glands. A pair of endocrine glands located on the surface of the kidneys. The adrenal glands produce corticosteroid hormones such as cortisol, aldosterone, and the reproductive hormones.

Analgesic. A medication or treatment that relieves pain.

Arthritis. Literally means joint inflammation but is often used to indicate a group of more than 100 rheumatic diseases. These diseases affect not only the joints but also other connective tissues of the body, including important supporting structures such as muscles, tendons, and ligaments, as well as the protective covering of internal organs.

Chronic disease. An illness that lasts for a long time, often a lifetime.

Connective tissue. The supporting framework of the body and its internal organs.

Cortisol. A hormone produced by the adrenal cortex, important for normal carbohydrate metabolism and for a healthy response to stress.

Fibromyalgia. A chronic syndrome that includes a history of widespread pain lasting more than 3 months and other general physical symptoms including fatigue, waking unrefreshed, and cognitive (memory or thought) problems.

Fibrous capsule. A tough wrapping of tendons and ligaments that surrounds the joint.

Inflammation. A characteristic reaction of tissues to injury or disease. It is marked by four signs: swelling, redness, heat, and pain. Inflammation is not a symptom of fibromyalgia.

Joint. A junction where two bones meet. Most joints are composed of cartilage, joint space, fibrous capsule, synovium, and ligaments.

Ligaments. Bands of cordlike tissue that connect bone to bone.

Muscle. A structure composed of bundles of specialized cells that, when stimulated by nerve impulses, contract and produce movement.

Nonsteroidal anti-inflammatory drugs (NSAIDs). A group of drugs, such as aspirin and aspirin-like drugs, used to reduce inflammation that causes joint pain, stiffness, and swelling.

Pituitary gland. A pea-sized gland attached beneath the hypothalamus at the base of the skull that secretes many hormones essential to bodily functioning. The secretion of pituitary hormones is regulated by chemicals produced in the hypothalamus.

Sleep disorder. A disorder in which a person has difficulty achieving restful, restorative sleep. In addition to other symptoms, people with fibromyalgia usually have a sleep disorder.

Tendons. Fibrous cords that connect muscle to bone