G-H

Gadolinium: An intravenous contrast agent used with magnetic

resonance imaging.

Gallstone (cholelithiasis): A solid formation in the gallbladder or

bile duct composed of cholesterol and bile salts.

γ-Aminobutyric acid (GABA): An inhibitory neurotransmitter.

Gamma knife: A type of radiosurgery (radiation therapy)

machine that acts by focusing low-dosage gamma radiation

from many sources on a precise target.

Gastric bypass: A surgical procedure for weight loss that elicits

its effectiveness through malabsorption and gastric volume

limitation. The procedure involves full partitioning of the

proximal gastric segment into a jejunal loop.

Gastritis: Inflammation of stomach lining.

Gastroparesis: A form of autonomic neuropathy involving nerves

of the stomach. It may include nausea, vomiting, feeling full,

bloating and lack of appetite. It may cause wide fluctuations

in blood sugars due to insulin action and nutrient delivery not

occurring at the same time.

Gastrostomy: Operative placement of a new opening into the

stomach usually associated with feeding tube placement.

Generalized seizures: A seizure where the entire cerebral cortex

is involved from the onset of the seizure.

Geniculate nucleus: The portion of the brain that processes

visual information from the optic nerve and relays it to the

cerebral cortex.

Genotype: The genetic constitution of an individual.

Geriatric syndrome: Age-specific presentations or differential

diagnoses, including visual and hearing impairment,

malnutrition and weight loss, urinary incontinence, gait

impairment and falls, osteoporosis, dementia, delirium, sleep

problems, and pressure ulcers; commonly seen conditions in

older patients.

Gleason score: System of histological grading used in prostate

cancer. Individual scores range from 2 to 5. The two highest

scores from each sample are combined for a total score (up to

10). Higher scores indicate higher grade and more aggressive

tumor.

Glomerular filtration rate (GFR): The volume of plasma that

is filtered by the glomeruli per unit time, usually expressed as

mL/min or mL/min/1.73 m2 (and in some areas in SI units

of mL/s or mL/s/m2), which adjusts the value for body surface

area. This is the primary index used to describe overall renal

function.

Glomerulonephritis: Glomerular lesions that are characterized

by inflammation of the capillary loops of the glomerulus.

These lesions are generally caused by immunologic, vascular,

or idiopathic diseases and lead to high blood pressure and

possible loss of kidney function.

Glucagon: Hormone involved in carbohydrate metabolism that is

produced by the pancreas and released when glucose levels in

the blood are low. When blood glucose levels decrease, the liver

converts stored glycogen into glucose, which is released into the

bloodstream. The action of glucagon is opposite of insulin.

Gluconeogenesis: Formation of glucose from precursors other

than carbohydrates especially by the liver and kidney using

amino acids from proteins, glycerol from fats, or lactate

produced by muscle during anaerobic glycolysis.

Glucosuria: Presence of glucose in the urine.

Glutamate: An excitatory amino acid found in the central

nervous system.

Glycogenolysis: The process by which glycogen is broken down

to glucose in body tissues.

Goiter: An enlargement of the thyroid gland, causing a swelling

in the front part of the neck.

Gonioscopy: Examination of the anterior chamber angle. A

gonioprism or Goldman lens is used to perform gonioscopic

evaluation.

Graft-versus-host disease: A condition that results from donor

immune cells attacking the normal tissue of a hematopoietic

stem cell transplant recipient.

Graft-versus-tumor effect: An immune response directed at a

patient’s malignant cells that is the result of donor immune cell

activation.

Grandiosity: Exaggerated sense of self-importance, ideas, plans,

or abilities.

Granuloma: Organized collection of macrophages designed to

wall off a foreign body or infectious pathogen that cannot be

eliminated.

Gummatous: A small, soft swelling that is characteristic of the

late stages of syphilis and generally occurs in the connective

tissue of the liver, brain, testes, and heart.

Gut-associated lymphoid tissue: Lymphoid tissue, including

Peyer patches, found in the gut that are important for providing

localized immunity to pathogens.

Guttate psoriasis: Characterized by a heavy or light sprinkling of

teardrop-like, salmon-pink papules covered with a fine scale.

These lesions are found primarily on the trunk and proximal

extremities.

Gynecomastia: Excessive development of the breasts in males.

HACEK: Group of fastidious gram-negative bacteria consisting

of Haemophilus spp., Aggregatibacter actinomycetemcomitans,

Cardiobacterium hominis, Eikenella corrodens, and Kingella

kingae.

Hashimoto Disease: Condition in which the immune system attacks

the thyroid gland; may result in hypothyroidism. Symptoms may

include fatigue, weight gain, pale or puffy face, feeling cold, joint

and muscle pain, constipation, dry and thinning hair, heavy

menstrual flow or irregular periods, depression, a slowed heart

rate, and problems getting pregnant and maintaining pregnancy.

It occurs more commonly in women than in men.

Health literacy: Degree to which individuals have the capacity to

obtain, process, and understand basic health information and

services needed to make appropriate health decisions.

Heberden nodes: Hard, bony enlargement of the distal

interphalangeal (terminal) joint of a finger or toe.

Hematemesis: Vomiting blood from gastric or esophageal

bleeding; in cirrhosis this is caused by variceal bleeding.

Hematochezia: Passage of stool that is bright red or maroon,

usually because of bleeding from the lower gastrointestinal tract.

Hematogenous: Spread of infection via the blood stream.

Hematoma: A localized swelling in an organ or soft tissue that

is filled with clotted or partially clotted blood resulting from a

break in a blood vessel wall.

Hemiparesis: Weakness on one side of the body.

Hemisensory deficit: Loss of sensation on one side of the body.

Hemithorax: A single side of the trunk between the neck and the

abdomen in which the heart and lungs are situated.

Hemoptysis: The expectoration of blood or blood-tinged sputum

from the larynx, trachea, bronchi, or lungs.

Heparin-induced thrombocytopenia: A clinical syndrome of IgG antibody production against the heparin-platelet factor 4 complex occurring in approximately 1% to 5% of patients exposed to either heparin or low-molecular weight heparin. Results in excess production of thrombin, platelet aggregation, and thrombocytopenia (due to platelet clumping), often leading to venous and arterial thrombosis, amputation of extremities, and death.

Hepatic encephalopathy: Confusion and disorientation experienced by patients with advanced liver disease due to accumulation of ammonia in the bloodstream.

Hepatic steatosis: Accumulation of fat in the liver.

Hepatocellular carcinoma: Cancer of the liver.

Hepatorenal syndrome: Acute kidney injury occurring in individuals with disease of the liver or biliary tract due to decreased renal blood flow and conditions that damage both organs.

Hepatotoxicity: Toxicity to the liver causing damage to liver cells.

Herd immunity: The resistance to the spread of a contagious

disease within a population, if a sufficiently high proportion

of the people are immune to the disease, such as through

vaccination.

Herniation: Abnormal protrusion of an organ or other structure through a defect or natural opening in a covering, membrane, muscle, or bone (eg, protrusion of the brain through the cranial wall).

Hesitancy: A decrease in the force of the stream of urine usually

the result of an obstruction or stricture between the bladder

and the external urethral orifice.

Heteroreceptor: A site on a neuron that binds a neurotransmitter other than that released by the neuron.

Heterotopic: Placing a transplanted organ into an abnormal

anatomic location.

Heterozygous: Having different alleles at a gene locus.

Hiatal hernia: Protrusion of a portion of the stomach through

the esophageal hiatus of the diaphragm.

Hirsutism: Excessive body and facial hair, especially in the

female.

Histocompatibility: State of having antigenic similarities that prevent donor hematopoietic stem cells from being rejected by the recipient.

Homeostenosis: Impaired capability to withstand stressors and decreased ability to maintain physiological and psychosocial homeostasis; a state commonly found in elderly.

Homozygous: Having identical alleles at a gene locus.

Hormone receptor-positive: Expression of estrogen and/or

progesterone receptors in breast cancer cells.

Hot flashes: A feeling of warmth that is commonly accompanied

by skin flushing and mild to severe perspiration.

Human epidermal growth factor receptor type 2 (HER2)-positive: Tumor positivity is defined by immunohistochemistry (3+ when > 10% of the cells harbor complete membrane staining) and FISH (fluorescence in situ hybridization) (if the number of HER2 gene copies is > 6 or the HER2/chromosome 17 ratio is > 2).

Human leukocyte antigens (HLA): Groups of genes found on

the major histocompatibility complex that contain cell-surface

antigen presenting proteins. The body uses HLA to distinguish

between self cells and non-self cells.

Humoral: Relating to the body fluids, especially with regard

to immune responses involving antibodies in body fluids as

distinct from cells.

Hydrocephalus: A condition marked by accumulation of cerebral

spinal fluid in the brain resulting in increased pressure inside

the skull.

Hydronephrosis: Swelling of the renal pelvis and calyces of the

kidney due to a back-up of urine due to obstruction.

Hyperalgesia: An exaggerated intensity of pain sensation.

Hypercalcemia: Excessive amount of calcium in the blood.

Hypercalciuria: Excessive amount of calcium in the urine.

Hypercapnia: Excessive carbon dioxide in the bloodstream,

typically caused by inadequate respiration.

Hypercoagulable state: A disorder or state of excessive or

frequent thrombus formation; also known as thrombophilia.

Hyperemesis gravidarum: A rare disorder of severe and persistent

nausea and vomiting during pregnancy that can result in

dehydration, malnutrition, weight loss, and hospitalization.

Hyperglycemic hyperosmolar nonketotic syndrome: Severe

increase in serum glucose concentration without the production

of ketones, leading to an increase in serum osmolality and

symptoms such as increased thirst, increased urination,

weakness, fatigue, confusion, and in severe cases convulsions

and/or coma.

Hyperopia: Farsightedness.

Hyperpigmentation: A common darkening of the skin which

occurs when an excess of melanin forms deposits in the skin.

Hypertrichosis: Excessive growth of hair.

Hyphae: A long, branching multicellular filamentous form of a

fungus.

Hypocretin: A wake-promoting hypothalamic neuropeptide

whose deficiency is involved in the pathophysiology of

narcolepsy.

Hypogammaglobulinemia: Reduced levels of antibodies.

Hypogonadism: A medical condition resulting from or characterized by abnormally decreased functional activity of the gonads,

with retardation of growth and sexual development. Associated

with testosterone deficiency resulting from either testicular or

pituitary/hypothalamic diseases. Presenting symptoms differ

according to the timing of disease onset in relation to puberty.

Hypomimia: Lack of facial expression. Often termed masked

face.

Hypophonia: Decreased voice volume.

Hypopituitarism: A clinical disorder characterized by complete

or partial deficiency in pituitary hormone production.

Hypoxemia: Deficiency of oxygen in the blood.

Hypoxia: Deficiency of oxygen in body tissues.

Hysterectomy: An operation to remove a woman’s uterus.