Medical Conditions

Hearing loss is the reduced ability to hear sound. Deafness is the complete inability to hear sound. Deafness and hearing loss have many causes and can occur …

The heart is one of the largest muscles in the body. The wall of the heart is the muscle that does the pumping, and it is called the myocardium. In a heart attack, …

Heat stroke is also known as sunstroke, thermic fever, or siriasis. It happens when the body's mechanisms for controlling temperature fail. Heat stroke is a …

Hemochromatosis is primarily an inherited (genetic) condition that allows too much iron to be absorbed and stored throughout the body. It's one of the most common …

Hemophilia is a rare bleeding disorder in which the blood does not clot normally. People with hemophilia have little or no blood clotting factors, which are needed …

Hemorrhoids, also called "piles," are swollen tissues that contain veins. They are located in the wall of the rectum and anus and may cause minor bleeding …

Hepatitis is the medical term for inflammation of the liver. Hepatitis may be acute (lasting only for the short term, after which a person recovers) or chronic …

Hepatitis is the medical term for inflammation of the liver. The hepatitis C virus is one of the many causes of inflammation of the liver. Liver …

A hernia occurs when a portion of tissue in your body bulges into or penetrates a weakened muscle area. Theoretically, hernias can happen anywhere in your …

The spine is made up of cylindrical bones called vertebrae. Between the bones of the spine are small discs made of a thick layer of cartilage on the outside and a …

Heart disease is one of the leading causes of death worldwide, and people who have abnormally high pressure in their arteries are far more likely than others to die …

Cholesterol is a fatty substance your body needs to rebuild its cells and to make certain hormones. It's carried throughout your body in your bloodstream. Your …

AIDS (acquired immune deficiency syndrome) was first recognized in North America in the early 1980s. It is caused by a virus known as HIV (human immunodeficiency …

Hives, called urticaria by doctors, is one of the most common causes of skin inflammation. Up to 20% of the population will suffer from urticaria at least once in …

Hodgkin lymphoma is the name for a group of cancers that start in the lymph nodes and then spread to surrounding areas of the body. Lymph nodes are …

The human papillomavirus (HPV) is a virus that causes skin and mucous membrane (the moist lining of body cavities such as the mouth and nose that connect with the …

Huntington's disease, also called Huntington's chorea, is a hereditary condition that affects the brain, specifically an area called the basal ganglia (located deep …

Approximately 4 million sweat glands cover the body and produce the clear liquid that we know as sweat. The body produces sweat to help regulate its …

The thyroid is a gland located in your neck, just beneath the Adam's apple. It releases hormones – thyroxine (T4) and triiodothyronine (T3) – that …

Hypoglycemia occurs when the level of glucose (sugar) in the blood is too low. Normally, your body keeps your blood glucose within a concentration range of …

Hypothermiaoccurs when you have abnormally low body temperature. Normal body temperature is around 37°C (98.6°F), as measured by mouth. Hypothermia is …

The thyroid is a gland located in the neck below the Adam's apple. It helps control the body's metabolic rate by producing the hormones thyroxine (T4) and …

IgA nephropathy, also called Berger's disease, is a kidney disorder that causes inflammation of the glomeruli, the individual filtering units of the …

Impetigo, also known as pyoderma, is a contagious skin infection caused by bacteria. Bacteria enter cuts, scrapes, cracked skin or insect bites leading to the …

Infectious mononucleosis (called "mono" for short) is caused by the Epstein-Barr virus (EBV), a virus that affects nearly everybody at some …

Infertility is usually defined as the inability to become pregnant after 1 year of vaginal intercourse without birth control. Without contraception, frequent …

The flu is a respiratory (i.e., nose, throat, and lung) infection that can be caused by influenza viruses. Many people use the word "flu" when they …

In North America, there are very few types of insects that carry venom or poison, and none whose venom is dangerous. However, it is possible for an insect bite or …

Insomnia can refer to difficulty getting to sleep, difficulty staying asleep, waking up early without being able to return to sleep, or a combination of the …

The blood that circulates throughout the body performs a number of critical functions. It delivers oxygen, removes carbon dioxide, and carries life-sustaining …