Articles In This Section
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A to Z: Hypothyroidism
Hypothyroidism is when the thyroid gland doesn't send enough thyroid hormone into the blood.
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A to Z: Hypothermia
Hypothermia is a medical emergency resulting from dangerously low body temperature.
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A to Z: Hypospadias
Hypospadias is a birth defect in which the tube that carries urine out of the body, called the urethra, opens on the underside of the penis.
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A to Z: Hyposmolality
Learn about metabolic conditions and conditions that can affect fluid and electrolyte levels in the blood.
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A to Z: Hypoplastic Left Heart Syndrome
Learn about hypoplastic left heart syndrome, a rare and serious defect of the heart.
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A to Z: Hyponatremia
Hyponatremia is an abnormally low level of sodium in the blood.
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A to Z: Hypoglycemia
Learn more about hypoglycemia, a condition where glucose levels drop below normal.
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A to Z: Hydromyelia
Learn about the central nervous system and conditions that can affect the spinal cord.
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A to Z: Herpangina
Learn more about viral infections and conditions that affect the mouth and throat.
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A to Z: Hydrocephalus
Hydrocephalus (sometimes called "water on the brain") is a brain condition that happens when cerebral spinal fluid (CSF) is unable to drain from the brain.
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A to Z: Hydrocele
A hydrocele is a collection of fluid around the testicle within the scrotum.
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A to Z: Hunter Syndrome
See: Mucopolysaccharidosis (Hunter Syndrome).
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A to Z: Hives
Learn about urticaria, the red raised bumps or welts on the skin that are commonly called hives.
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A to Z: Hirschsprung Disease
Learn about Hirschsprung disease, a birth defect that prevents a child from passing bowel movements.
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A to Z: Hidradenitis
In this condition, which often begins during the teen years, lumps form under the skin in areas like the armpit or groin. Learn more here.
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A to Z: Herpes Zoster
Learn about viral infections and causes of skin conditions.
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A to Z: Herpes Simplex 1
Learn about viral infections, types of herpes, and conditions that affect the mouth and face.
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A to Z: Hernia, Umbilical
Learn about hernias and conditions that affect the abdomen and bellybutton.
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A to Z: Hydronephrosis
Learn more about hydronephrosis (swollen kidney) in children.
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A to Z: Hyperkalemia
Learn more about diseases and conditions of the blood and kidneys.
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A to Z: Hyperopia
Hyperopia is farsightedness, a common condition in which someone can see things in the distance clearly, but things that are closer appear blurry.
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A to Z: Hypertension, Intracranial
Learn about causes of vision loss and conditions that can affect the brain and nervous system.
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A to Z: Hypertension, Primary
Learn about types of high blood pressure and conditions that can affect the heart and blood vessels.
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A to Z: Hypertension, Pulmonary
Learn about types of high blood pressure and conditions that can affect the lungs and heart.
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A to Z: Hypertriglyceridemia
In this common condition, there is a high level of fats called triglycerides in the blood. Learn how this is related to diet, lifestyle, and heart disease here.
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A to Z: Hypertrophy, Tonsillar (Enlarged Tonsils)
Tonsillar hypertrophy, or enlarged tonsils, can happen due to an ongoing (chronic) condition or a temporary effect of an infection.
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A to Z: Hyphema
Hyphema is a condition that happens when blood collects in the front part of the eye.
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A to Z: Hypogammaglobulinemia
Learn about complications of white blood cell deficiencies and conditions that affect the immune system.
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A to Z: Hernia, Inguinal
Learn about hernias and conditions that affect the lower abdomen and reproductive organs.
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A to Z: Hernia, Incisional
Learn about hernias and potential complications of abdominal surgery.
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A to Z: Hernia, Hiatal
Learn about hernias and conditions that affect the stomach, esophagus, and upper gastrointestinal tract.
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A to Z: Hernia, Epigastric
Learn about hernias and conditions that affect the abdomen and abdominal muscles.
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A to Z: Hernia, Bilateral
A bilateral hernia is an opening or weakness in the abdominal wall on both sides of the groin. Learn about it here.
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A to Z: Hematuria (Blood in Urine)
Learn more about hematuria (blood in urine) and how it's treated.
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A to Z Symptom: Headache
Headaches are common in kids and teens, and can have a wide range of causes. Most can be managed at home.
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A to Z: Hand, Foot, and Mouth Disease
Hand, Foot, and Mouth disease is a common contagious illness caused by viruses from the enterovirus family, most commonly the coxsackievirus.
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A to Z: Hashimoto’s Thyroiditis
Hashimoto's thyroiditis is a chronic (ongoing) condition where the body's immune system attacks the thyroid, a gland in the neck that makes thyroid hormone.
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A to Z: Hay Fever
See: Rhinitis, Allergic.
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A to Z: Hearing Loss, Conductive
Learn about causes of hearing loss and conditions that can affect the outer ear and middle ear.
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A to Z: Hearing Loss, Mixed
Learn about causes of hearing loss and conditions that can affect the ear and auditory nerve.
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A to Z: Hearing Loss, Neural
Learn about causes of hearing loss and conditions that can affect the auditory nerve.
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A to Z: Hearing Loss, Perceptive
See: Hearing Loss, Sensorineural.
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A to Z: Hearing Loss, Sensorineural
Learn about causes of hearing loss and conditions that can affect the inner ear and auditory nerve.
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A to Z: Hemangioma
Learn more about hemangiomas, common birthmarks in infants.
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A to Z: Hematemesis
Learn more about diseases and conditions of the stomach and digestive system.
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A to Z: Hemiplegia
Learn about congenital disorders and conditions that affect the brain and central nervous system.
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A to Z: Hemophilia A (Factor VIII Deficiency)
In factor VIII deficiency (hemophilia A), the body doesn't make enough factor VIII (factor 8), one of the substances the body needs to form a clot.
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A to Z: Hemophilia B (Factor IX Deficiency)
In hemophilia B (factor IX deficiency), the body doesn't make enough factor IX (factor 9), one of the substances the body needs to form a clot.
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A to Z: Hemorrhage, Intracerebral
Learn about causes of stroke and conditions that can affect the brain.
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A to Z: Hemorrhage, Subconjunctival
This condition happens when a blood vessel on the surface of the eye breaks open and leaves a red spot on the white of the eye. Learn more here.
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A to Z: Henoch-Schönlein Purpura (HSP)
Learn about Henoch-Schönlein purpura, a condition in which capillaries in the skin, kidneys, and intestinal tract become inflamed and leak.
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A to Z: Hereditary Angioedema
In this inherited condition, people can have attacks of swelling in the skin, airways, and intestines. Learn about hereditary angioedema here.
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A to Z: Hemophagocytic Syndrome
Hemophagocytic syndrome (HPS) is a rare and potentially life-threatening blood disorder of the immune system. It mostly affects infants and children but can develop at any age.
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A to Z: Hypoxemia
Hypoxemia is a condition in which there is a lower than normal level of oxygen in the blood.
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A to Z: Head Injury
Learn more about head injuries (head trauma).