Use the A-Z list to browse more than 6,000 health-related topics in our library. Clicking on a term opens the definition and, in most cases, links to more information.
"Uncomplicated Diverticular Disease" is more commonly referred to as "Diverticulosis" in the medical community. Diverticulosis
The formation of generally harmless small pouches or diverticula in the colon. If the diverticula become infected or irritated, diverticulitis develops. More Information on Diverticulosis: Diverticulitis & Diverticulosis
The portion of the mind where psychic activity takes place of which the person is unaware. Elements of psychic makeup, including memories or repressed desires, cannot be perceived or controlled but may affect conscious thoughts and behavior. More Information on Unconscious: Emotional Health Basics
"Underactive Thyroid" is more commonly referred to as "Hypothyroidism" in the medical community. Hypothyroidism
Also Known As: "Hashimoto Disease"
A disorder in which the thyroid gland is not producing enough thyroid hormones to meet the body's needs. Most people with hypothyroidism will need to take synthetic thyroid hormones for life to relieve symptoms and avoid long-term consequences. More Information on Hypothyroidism: Thyroid & Parathyroid
An abnormal bite that occurs when the lower teeth are located more to the front than the upper teeth when the mouth is closed. More Information on Underbite: Dental Braces & Alignment
"Underdeveloped Left Ventricle Syndrome" is more commonly referred to as "Hypoplastic Left Heart Syndrome" in the medical community. Hypoplastic Left Heart Syndrome
Also Known As: "Left Heart Hypoplasia, HLHS"
A heart defect that can be fatal unless repaired early in life. The chambers, valves and related vessels on the left side of the heart are so malformed that they cannot efficiently pump blood to the rest of the body. More Information on Hypoplastic Left Heart Syndrome: Pediatric Heart
Poor health resulting from the depletion of nutrients due to inadequate nutrient intake over time. It is often associated with poverty, alcoholism and some types of eating disorders. More Information on Undernutrition: Nutrition Basics
Over-the-counter medications do not require a prescription from a physician, but many contain the same ingredients found in prescription drugs. Understanding drug labels is important to avoid side effects and dangerous drug interactions. More Information on Understanding Drug Labels: Healthcare Basics
A method of calculating body density by measuring the volume of water displaced when a person is fully submerged in a special water tank. More Information on Underwater Weighing: Weight & Obesity Basics
Body weight in relation to height that is found to be less than an established standard for a person of that height, age and gender. More Information on Underweight: Nutrition Basics
Also Known As: "Undifferentiated Type Schizophrenia"
A form of schizophrenia in which a person has many of the symptoms present in the various individual types or the disease, but not enough symptoms of any one of them to define it as a specific type of schizophrenia. More Information on Undifferentiated Schizophrenia: Schizophrenia & Psychosis
Physical complaints that cannot be fully explained by any general medical condition or by the direct effects of a substance. Includes disorders that do not satisfy the criteria for other somatoform disorders. More Information on Undifferentiated Somatoform Disorder: Factitious & Related Disorders
A form of schizophrenia in which a person has many of the symptoms present in the various individual types or the disease, but not enough symptoms of any one of them to define it as a specific type of schizophrenia. More Information on Undifferentiated Type Schizophrenia: Schizophrenia & Psychosis
"Undulant Fever" is more commonly referred to as "Brucellosis" in the medical community. Brucellosis
Also Known As: "Brucella Infection"
A bacterial disease transmitted to humans by infected animals, meat and milk products. It occurs when bacteria are inhaled, ingested or come in contact with skin. Flu-like symptoms result. Serious infections can damage the heart or nervous system. More Information on Brucellosis: Bioterror Related Diseases
A tooth that has not yet penetrated the gum and still remains hidden within the jaw and beneath the gum. More Information on Unerupted Tooth: Pediatric Dental
"Unexplained Weight Gain" is more commonly referred to as "Weight Changes (Unexplained)" in the medical community. Weight Changes (Unexplained)
Also Known As: "Unexplained Weight Loss"
Significant weight changes that are not explainable by lifestyle changes (e.g., diet, exercise) or temporary illness (e.g., stomach flu) should be reported to a physician. Such gains or losses may be a sign of a number of diseases, including cancer. More Information on Weight Changes (Unexplained): Weight & Obesity Basics
"Unexplained Weight Loss" is more commonly referred to as "Weight Changes (Unexplained)" in the medical community. Weight Changes (Unexplained)
Also Known As: "Unexplained Weight Gain"
Significant weight changes that are not explainable by lifestyle changes (e.g., diet, exercise) or temporary illness (e.g., stomach flu) should be reported to a physician. Such gains or losses may be a sign of a number of diseases, including cancer. More Information on Weight Changes (Unexplained): Weight & Obesity Basics
"UNFAO" is more commonly referred to as "Food and Agriculture Organization" in the medical community. Food and Agriculture Organization
Also Known As: "United Nations Food and Agriculture Organization, FAO"
A United Nations agency that serves as a forum for nations to negotiate agreements and debate policy. It also helps developing countries modernize and improve agriculture, forestry and fisheries practices and works to ensure good nutrition for all.
"Unfractionated Heparin" is more commonly referred to as "Heparin" in the medical community. Heparin
Also Known As: "Liquaemin, Heparin Leo, Calciparine"
A brand of anticoagulants, medications that decrease the ability of the blood to clot. While clotting is a necessary and life-sustaining function, anticoagulants reduce the risk of a clot forming and blocking blood flow through a major blood vessel. More Information on Heparin: Heart Drug & Medication
A condition that occurs when an organism lives, feeds and breeds under the skin. Its cause is unknown, but it sometimes follows a lice and/or scabies outbreak. More Information on Unidentified Skin Parasite Infection: Skin Related Infections
"Unilateral Oophorectomy" is more commonly referred to as "Oophorectomy" in the medical community. Oophorectomy
Also Known As: "Bilateral Salpingo Oophorectomy, Ovary Removal, Salpingo Oophorectomy, Ovariectomy, Bilateral Oophorectomy, Salpingectomy Oophorectomy, Bilateral Ovariectomy"
Surgical removal of one (unilateral) or both (bilateral) ovaries. It is used to treat cancers, cysts or uterine disorders. It may be performed alone of in combination with removal of the uterus (hysterectomy) or fallopian tubes (salpingectomy). More Information on Oophorectomy: Uterine & Ovarian Health
"Unipolar Depression" is more commonly referred to as "Major Depression" in the medical community. Major Depression
Also Known As: "Major Depressive Episode, Depressive Disorder, Major Depressive Disorder, Clinical Depression, Depressive Episode, Depression"
A feeling of intense sadness that lasts most of the day, nearly every day, for at least two weeks. It requires active clinical observation and treatment. More Information on Major Depression: Depression & Bipolar
The basic measure of insulin. Most insulin produced in the United States is U-100 (100 units of insulin per milliliter or cubic centimeter of solution). More Information on Unit of Insulin: Insulin
"United Nations Food and Agriculture Organization" is more commonly referred to as "Food and Agriculture Organization" in the medical community. Food and Agriculture Organization
Also Known As: "FAO, UNFAO"
A United Nations agency that serves as a forum for nations to negotiate agreements and debate policy. It also helps developing countries modernize and improve agriculture, forestry and fisheries practices and works to ensure good nutrition for all.
The coordinating body for the registration and administration of U.S. organ transplant procurement. UNOS runs a network comprising all transplant organizations and laboratories, setting policies and matching organ donors to registered recipients.
"Univentricular Heart" is more commonly referred to as "Single Ventricle" in the medical community. Single Ventricle
A heart defect in which a newborn has one normal ventricle (a lower chamber of the heart) and one ventricle that is either deformed or absent. The two upper chambers (atria) are normal. More Information on Single Ventricle: Pediatric Heart
The coordinating body for the registration and administration of U.S. organ transplant procurement. UNOS runs a network comprising all transplant organizations and laboratories, setting policies and matching organ donors to registered recipients.
A type of fat found in many plant and nut oils. The two main types are polyunsaturated fat and monounsaturated fat. They do not increase levels of cholesterol or triglycerides, and some may even help to reduce these levels. More Information on Unsaturated Fat: Fats & Oils
Angina (chest pain, pressure or discomfort) that is unpredictable because it does not occur during or after a trigger such as stress or exercise. The patient notes that chest discomfort may occur more readily, more frequently or even at time of rest. More Information on Unstable Angina: Chest & Related Pain
Also Known As: "Brittle Diabetes, Labile Diabetes"
A type of diabetes in which a person's blood glucose level swings from high to low and back to high. Also called "brittle diabetes" or "labile diabetes." More Information on Unstable Diabetes: Diabetes & Endocrine Basics
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