Acromegaly: A disorder associated with excessive growth of bone and soft tissue in the adult, resulting from the excess growth hormone (GH) secretion by the pituitary gland. Common disorder in cats; almost always caused by a GH-secreting pituitary adenoma.
ACTH: see Adrenocorticotropic hormone
Adrenocorticotropic hormone: A hormone produced by the pituitary gland that stimulates the secretion of cortisone and other hormones by the adrenal cortex. Abbreviated as ACTH, and synonymous with the term corticotrophin.
Addison’s disease: A disease caused by partial or total failure of adrenocortical function (the function of the adrenal cortex), characterized by poor appetite, weight loss, weakness, and vomiting. Also called hypoadrenocorticism or adrenocortical insufficiency.
Adenoma: A benign (non-cancerous) tumor, such as a thyroid or pituitary adenoma.
Adrenalectomy: An operation that removes one or both adrenal glands.
Adrenaline: See epinephrine.
Adrenocortical insufficiency: See Addison’s disease
Adrenal cortex: The outer layer of the adrenal gland that secretes hormones, including cortisol and aldosterone, which are vital to the body.
Adrenal glands: The two adrenal glands are located on the top of each kidney. Each gland consists of a medulla (the center of the gland), surrounded by the cortex (outer core).
Adrenal medulla: The inner portion of the adrenal gland that secretes the catecholamine hormones adrenaline (epinephrine) and noradrenaline (norephinephrine).
Aldosterone: A hormone secreted by the adrenal cortex that affects blood pressure and sodium and potassium balance. See mineralocortioids.
ADH: See Antidiuretic hormone.
Amlodipine: A drug used to treat hypertension (high blood pressure). The trade name is Norvasc.
Androgens: Male sex hormones secreted by the gonads (testes). Small amounts are also secreted by the adrenal cortex.
Antidiuretic hormone: A hormone secreted by the posterior lobe of the pituitary gland that constricts blood vessels, raises blood pressure, and reduces urination. Abbreviated as ADH; also called vasopressin. ADH deficiency leads to the syndrome of diabetes insipidus.
Antithyroid drugs: Medications that reduce the thyroid gland's ability to produce thyroid hormone. The two main antithyroid drugs used in veterinary medicine are methimazole and carbimazole.
Benazepril: A drug used to treat hypertension (high blood pressure) and renal (kidney) protein loss. The trade names for the drug include Lotensin or Fortekor.
Beta-blocking drugs: Medications that help alleviate the signs (nervousness, rapid heart rate) caused by excess T4 and T3 (see hyperthyroidism). These drugs act by blocking the effect of the catecholamines.
Calcitonin: A hormone secreted by the thyroid gland which controls the levels of calcium and phosphorous in the blood.
Catecholamines: see epinephrine and norepinephrine
Carbimazole: An antithyroid medication used to treat hyperthyroidism.
CT Scan / CAT Scan: See computed tomography
Computed tomography: A non-invasive procedure that takes cross-sectional images of the brain or other internal organs to detect abnormalities that may not show up on a routine X-ray.
Conn’s syndrome: A syndrome caused by an increased secretion of aldosterone from the adrenal gland (usually an adrenal). Disorder is characterized by high blood pressure and low blood potassium levels; weakness and blindness are common signs. Also called hyperaldosteronism.
Corticosteroids: Hormones produced by the adrenal cortex. The corticosteroids include cortisol (hydrocortisone), aldosterorone, and the adrenal sex steroids.
Corticotropin: See ACTH and adrenocorticotropic hormone.
Cortisol: See hydrocortisone.
Cushing’s syndrome: A syndrome caused by an increased secretion of cortisol from a tumor of the adrenal cortex or from an ACTH-secreting lesion in the pituitary gland. Also, can occur by excessive intake of glucocorticoids. Disorder is characterized by increase thirst and urination, enlarged abdomen, and hair loss on the trunk. Synonymous with the term hyperadrenocorticism.
Desiccated thyroid: A crude preparation made of animal thyroid glands. It was the first available source of thyroid hormone (T4). Because it is difficult to absorb and may contain impurities, desiccated thyroid preparations are no longer widely used.
Desmopressin: A synthetic analogue of antidiuretic hormone (ADH or vasopressin) used as a drug to treat central diabetes insipidus. The common trade name for desmopressin is DDAVP.
Diabetes mellitus: A disease caused by partial or total failure of insulin secretion from the pancreas. This causes the body to metabolize carbohydrates, fats, and proteins abnormally. The disorder is characterized by increased sugar levels in the blood and urine, excessive thirst, frequent urination, and wasting. Unrelated to diabetes insipidus.
Diabetes insipidus: A chronic metabolic disorder characterized by intense thirst and excessive urination. It is caused by problems with antidiuretic hormone, a pituitary hormone responsible for maintaining hydration. Either the pituitary gland does not secrete enough of this hormone (called central diabetes insipidus), or the kidneys do not respond normally to the hormone (called nephrogenic diabetes insipidus).
Enalapril: A drug used to treat hypertension (high blood pressure). The trade names for the drug include Enacard or Vasotec.
Endocrine: Relating to endocrine glands or the hormones secreted by them.
Epinephrine: Hormone secreted by the medulla (central part) of the adrenal glands. Functions in the “fight or flight” response. Commonly known as “adrenaline.”
Estrogen: A hormone secreted by the ovaries that affects many aspects of the female body, including menstrual cycles and pregnancy. Small amounts of estrogen also secreted by adrenal cortex.
External radiation therapy: A type of radiation therapy that directs beams of high-energy X-rays or particles from outside of the patient’s body to kill cancer cells. During this type of radiation, high-energy beams come from special machines, such as linear accelerators (LINAC) or cobalt machines.
Felimazole: Trade name for methimazole, an antithyroid drug.
Free T4: Free thyroxine, a thyroid function test. Measures the non-protein bond fraction of T4 in the circulation.
Glucocorticoids: Any of a group of adrenocortical hormones (eg, cortisol, cortisone, prednisone, or dexamethasone) that regulate carbohydrate, protein, and fat metabolism. At higher doses, these hormones can have anti-inflammatory and immunosuppressive properties.
Glucagon: A protein hormone secreted by the pancreas that acts on the liver to stimulate glucose production and raise the blood sugar level.
Goiter: Enlargement of the thyroid gland for any reason. Goiter can be diffuse (general enlargement) or nodular (asymmetric enlargement). In animals, goiter is usually caused by a thyroid tumor, but may be seen in some types of congenital hypothyroidism.
Gonads: Ovaries or testes.
Gonadotropins: Hormones produced by the pituitary gland that regulate gonadal function. There are two gonadotropins: luteinizing hormone (LH) and follicle-stimulating hormone (FSH).
Graves' disease: A form of hyperthyroidism caused by an overactive, diffuse goiter that is often associated with exophthalmos (bulging eyes). This form of hyperthyroidism does not occur in dogs and cats.
Hashimoto's thyroiditis: Inflammation of the thyroid gland. Typically leads to a form of hypothyroidism.
Hormone: A chemical produced by an endocrine gland and released into the blood. It travels to other organs or parts of the body where it produces its effect.
Hydrocortisone: A hormone secreted by the adrenal cortex that affects metabolism and is necessary for life. Also called cortisol.
Hyper- (prefix): Over; excess; high; above normal.
Hyperadrenocorticism: See Cushing’s syndrome.
Hyperaldosteronism: See Conn’s syndrome.
Hyperparathyroidism: Overproduction of parathyroid hormone (PTH) by a diseased parathyroid gland (usually a parathyroid tumor). The excess PTH causes hypercalcemia (calcium level that is too high).
Hyperthyroidism: Condition caused by excess thyroid hormone secretion associated with symptoms of increased metabolic rate. Common in cats, usually caused by benign thyroid adenoma.
Hypo- (prefix): Under; deficient; low; below normal.
Hypoadrenocorticism: See Addison’s disease or Adrenocortical insufficiency
Hypogonadism: Disorder associated with the sex glands (gonads) producing little or no sex hormones. In males, these glands are the testes; in females, they are the ovaries.
Hypoparathyroidism: Lack of parathyroid hormones which leads to hypocalcemia (low blood calcium). Hypocalcemia can cause muscle spasms, tetany, and seizures.
Hypothyroidism: Condition caused by deficient thyroid hormone secretion associated with symptoms of decreased metabolic rate. Common in dogs.
Hypothalamus: The portion of the brain, located just above the brain stem, which controls and regulates the pituitary gland.
Insulin: The hormone released by the pancreas to reduce high blood glucose. Deficiency of this hormone results in diabetes mellitus.
Insulinoma: An insulin-secreting tumor of the pancreas, leading to hypoglycemia (low blood glucose).
Intravenous: Introducing a sterile fluid into the bloodstream through a vein.
Iodine: A non-metallic element found in food. It is necessary for normal thyroid function and is routinely added to table salt.
Islets of Langerhans: Groups of pancreatic cells that produce insulin and glucagon, the hormones that regulate and maintain normal blood glucose levels.
Levothyroxine (L-T4): Synthetic form of thyroxine (T4). Used in treatment of hypothyroidism.
Lysodren: The trade name for the drug mitotane, used to treat Cushing’s syndrome.
Magnetic resonance imaging (MRI) - A non-invasive procedure that creates two-dimensional images of internal organs, especially the brain and spinal cord, using magnetic fields. Commonly abbreviated as MRI.
Medulla: The central part of a gland (e.g., the adrenal medulla).
Metabolism: The use of calories (food energy) and oxygen to produce energy.
Methimazole: An antithyroid medication used to treat hyperthyroidism.
Mineralocorticoid: A group of steroid hormones made in the adrenal gland which act to regulate the balance of water and electrolytes in the body. The principal mineralocorticoid in dogs and cats is aldosterone.
Mitotane: A drug used to treat dogs with Cushing's syndrome.
MRI: See Magnetic resonance imaging.
Multi-nodular goiter: Enlarged thyroid gland with two or more nodules.
Myxedema: Specific form of cutaneous edema; often associated with severe hypothyroidism. Usually seen as mild to moderate swelling of the face and forehead, giving affected dogs a “tragic” facial expression.
Neoplasm: Any tumor or abnormal growth. May be benign or malignant.
Nodular goiter: Enlarged thyroid gland with one or more nodules. When associated with hyperthyroidism, also call "toxic" nodular goiter. This is the lesion found in many cats suffering from hyperthyroidism.
Norepinephrine: Hormone secreted by the medulla (central part) of the adrenal glands together with epinephrine (adrenaline). Functions in the “fight or flight” response. Commonly known as “noradrenaline.
Nuclear imaging: Medical imaging performed by administering a small dose of a radioactive tracer (radionuclide) and then scanning with a gamma camera. Also called scintigraphy or nuclear scanning. Thyroid scintigraphy is a powerful method for diagnosing hyperthyroidism and determining the stage of the disease.
Oxytocin: A hormone secreted by the pituitary gland that plays a role in
pregnancy and delivery. Also a major neurotransmittor in the brain.
Pancreas: The pancreas is an oblong, flattened gland located in the abdomen, adjacent to the stomach and small intestine. The pancreas secretes both digestive juices (enzymes) as well as two major hormones, insulin and glucagon.
Parathyroid glands: Four small glands located in the neck, near the thyroid gland. They produce parathyroid hormone, which controls the blood calcium level.
Parathyroid hormone: Hormone secreted by the parathyroid glands. It acts to raise the blood calcium level by increasing absorption of calcium from the diet and removing calcium from bones. Commonly abbreviated as PTH.
Parathyroidectomy: An operation that removes one or more parathyroid glands, usually parathyroid tumors.
Pheochromocytoma: A tumor of the adrenal medulla that secretes adrenaline (epinephrine), noradrenaline (norepinephrine) or both hormones. Symptoms may include increased thirst and urination, increased heart rate, and restlessness.
Pituitary dwarfism: Inherited dwarfism seen most commonly in German Shepherds. Condition results from pituitary growth hormone (GH) deficiency; but concurrent hypothyroidism can also occur. Dwarfism, progressive hair loss, and mental dullness are common signs
Pituitary gland: A small gland, about the size of a pea, located behind the eyes, at the base of the brain. Known as the “master” endocrine gland. Divided into an anterior and posterior part. The pituitary secretes a number of hormones that stimulate other endocrine glands (eg, thyroid, adrenal, testicles, and ovaries) to secrete their hormones (eg, T4, cortisol, testosterone, estrogen, respectively).
Progesterone: A sex hormone secreted by the ovaries that affect many aspects of the female body, including menstrual cycles and pregnancy. Small amounts of progesterone are also secreted by the adrenal cortex.
Prolactin: A hormone secreted by the pituitary gland that stimulates milk production in the mammary glands.
Propylthiouracil: An antithyroid medication used to treat hyperthyroidism. Commonly abbreviated PTU. Can be toxic in cats, so no longer used to treat feline hyperthyroidism.
PTH: See parathyroid hormone.
Radiation therapy: See Radioactive iodine, External radiation therapy.
Radioactive iodine: An isotope of iodine administered internally that is used to treat thyroid lesions, hyperthyroidism, and thyroid cancer. Also commonly referred to as I-131 or 131-I.
Radioiodine: See Radioactive iodine; I-131.
Radioiodine therapy: A procedure that in which radioiodine (radioactive iodine; I-131) is administered to treat hyperthyroidism and thyroid tumors.
Radiograph: Electromagnetic energy used to produce images of bones and internal organs. Commonly referred to as x-rays.
Scintigraphy: See Nuclear imaging.
Sex hormones: Sex hormones secreted by the gonads (testes and ovaries) and the adrenal cortex. Includes androgens, estrogens, and progestagens.
Sex steroids: See Sex hormones.
Subcutaneous injection: Administering a sterile fluid into the subcutis, the layer of just below the skin. Commonly abbreviated as SQ, SC, or sub-Q.
Suprarenal Glands. Another name for the adrenal glands. The adrenals are located above or on top of (i.e., supra) the kidneys (renal system).
T3: See triiodothyronine.
T4: See thyroxine.
Tapazole: Trade name for methimazole, an antithyroid drug.
Thyroidectomy: An operation that removes all or part of the thyroid gland.
Thyroid gland: A gland that makes and stores the thyroid hormones. Located in the lower part of the neck, below the Adam's apple, adjacent to the trachea (windpipe). In dogs and cats, it is composed of two separate thyroid lobes.
Thyroid hormone: Thyroid hormones are essential for the function of every cell in the body. They help regulate growth and the rate of chemical reactions (metabolism) in the body. See Thyroxine (T4) and Triiodothyronine (T3).
Thyrotropin: See thyroid stimulating hormone.
Thyroid stimulating hormone: A hormone produced by the pituitary that stimulates the thyroid gland to produce T3 and T4. Commonly referred to as TSH.
Thyroxine: The primary hormone secreted by the thyroid gland, which regulates metabolism. Commonly referred to as T4.
Triiodothyronine: The second hormone secreted by the thyroid gland, which regulates metabolism. Most of this hormone, however, is produced by conversion from T4. Commonly referred to as T3.
Trilostane: A drug used in to treat dogs and cats with Cushing's syndrome.
TSH: See thyroid stimulating hormone.
Tumor: A mass of tissue. It may be benign or malignant.
Vasopressin: A hormone secreted by the posterior lobe of the pituitary gland that constricts blood vessels, raises blood pressure, and reduces excretion of urine. Also called antidiuretic hormone or ADH.
Vetoryl: Trade name for trilostane, a drug used for treatment of Cushing’s syndrome.
Vitamin D: Actually a hormone rather than a vitamin, Vitamin D acts in concert with parathyroid hormone to maintain normal blood levels of calcium. The active form of vitamin D is also referred to as calcitriol.
Ultrasound: A diagnostic technique that uses high-frequency sound waves to create an image of the internal organs. Also called sonogram or ultrasonography.
X-ray (Radiograph): Electromagnetic energy used to produce images of bones and internal organs.