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116 Cards in this Set
- Front
- Back
Thyroid hormone is stored in which portion of the glandular tissue?
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The colloid in the follicle.
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The parafollicular cells of the thyroid gland secrete which hormone?
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Calcitonin.
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Where in the body is iodine converted to iodide?
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The GI tract.
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Is iodide actively or passively transported into the follicle cell?
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Actively by a Na/I symporter.
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Once inside the thyroid cell Iodide is oxidized to iodine and incorporated into what molecules?
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Tyrosine.
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Tyrosine is a component of which larger molecule?
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Thyroglobulin.
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T3 is comprised of which molecules?
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1 monoiodotyrosine + 1 diiodotyrosine→ triiodothionine.
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What molecules comprise T4?
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2 diiodotyrosine. |
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Which molecule is more potent T3 or T4?
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T3.
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What enzymes catalyze all reactions to form T3 or T4?
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Thyroperoxidase.
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When needed T3 and T4 are cleaved in the follicle cell and transported by what type of carrier?
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A protein; there are several carrier proteins.
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Which hormone is the most important regulator of thyroid hormone production?
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TSH.
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Sustained release of TSH results in what changes of the follicular cells?
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Hypertrophy and hyperplasia.
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Which hormone feeds back to decrease TSH secretion?
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T3.
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Within a non-thyroid cell T3 and T4 have what effects?
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Messenger RNA transcription and affects the mitochondria (increased oxygen consumption and therefore heat production).
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What effects does T3 and T4 have on carbohydrate metabolism?
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Generally catabolic: increases intestinal glc absorption/movement of glc into fat and muscle/ glycogen formation/small amount of glucogenolysis.
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What blood value is a hallmark for hypothyroidism?
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Hypercholesterolemia.
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What affect can inadequate T3 and T4 have on the fetus?
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Inhibition of mental activity.
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What effect does T3 and T4 have on the heart?
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Increase HR and contraction.
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What is the mechanism of action of methimazole?
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Inhibits thyroperoxidase.
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What is the T ½ of methimazole?
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4-6 hours.
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What is the safest and simplest therapy for hyperthyroidism?
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I 131.
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What radioactive particles does I-131 emit?
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Gamma and beta. |
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Which particle of I-131 causes the most damage to the thyroid?
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Beta (80% of the damage is within 2 mm).
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What percentage of cats become euthyroid with a single dose of I-131?
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90%.
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The thyroid lobe is located between what two anatomic structures?
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The common carotid (laterally) and the trachea (medially).
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What is the cause of 50% of hypothyroidism in dogs?
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Immune-mediated lymphocytic thyroiditis.
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Aside from lymphocytic thyroiditis what is another common cause of hypothyroidism in dogs?
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Idiopathic follicular atrophy; maybe the end result of thyroiditis.
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What are the clinicals signs of congenital hypothyroidism?
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Mental retardation and dwarfism.
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What is the most common endocrine disease of cats?
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Hyperthyroidism.
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Hyperthyroidism is very rare in dogs but may be due to what other disease?
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Thyroid carcinoma.
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What is the most common cause of hyperthyroidism in cats?
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Functional adenomatous hyperplasia.
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What is the appearance of the thyroid gland with adenomatous hyperplasia?
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Hypoechoic and often with cysts.
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What palpable clinical signs is present in 80% of cats with hyperthyroidism?
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Goiter.
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What changes in the heart can be seen radiographically in a hyperthyroid cat?
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Cardiomegaly is present 50% of the time.
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When are 90% of thyroid carcinomas detected?
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Ante-mortem.
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Is thyroid carcinoma usually unilateral or bilateral?
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Unilateral.
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Which dog breeds are at risk for thyroid carcinoma?
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Golden Retrievers and Beagles.
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Hyperthyroidism in cats is caused by thyroid carcinoma in what percentage of cats?
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2%.
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What are the clinical signs of thyroid carcinoma?
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Dysphagia and retching and regurgitation.
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T/F. Thyroid carcinomas are usually non functional.?
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True.
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Name the three lobes of the pituitary gland?
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Pars distalis (anterior). Pars nervosa (posterior). Pars intermedia.
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What two hormones does the posterior pituitary produce?
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ADH and Oxytocin.
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ADH and Oxytocin cause the release of what other hormones?
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None. They act directly.
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Where does the pituitary portal system terminate?
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In a capillary plexus of the hypothalamus.
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Which hormone affects mammary tissue development and lactation?
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Prolactin.
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Leutinizing hormone stimulates testosterone production from which cells?
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Leydig cells of the teste and the theca cells of the ovary (granulosa cell convert testosterone to estrogen in the female).
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ACTH increases the secretion of which hormone from the adrenal cortex?
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Cortisol but not aldosterone.
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What causes the release of ADH?
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Increased osmolality of body fluids.
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What is the effect of oxytocin?
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Contraction of myoepithelial cells in the mammary gland and the myometrium.
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What is Cushing’s disease?
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Pituitary dependent hyperadrenocorticism.
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What is Cushing’s syndrome?
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The constellation of abnormalities from chronic exposure to excessive glucocorticoids.
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What are the three main causes of Cushing’s syndrome?
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Excessive secretion of ACTH (usually from pituitary). Functional adrenal tumor. Iatrogenic.
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What is the second most common cause of Cushing’s syndrome?
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Functional adrenal tumor.
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In which species are the effects of hypercortisolism more debilitating?
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The dog.
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Which dog breed is predisposed to PDH?
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Boxer.
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Do dogs that are less than 20 kgs more prone to PDH or primary adrenal tumors?
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PDH (if they are greater than 20 kgs there’s a 50% chance there is a primary adrenal tumor).
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What is the cause of pU/pD in Cushing’s syndrome?
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Glucocorticoids reduce renal tubular resportion of water resulting in pU.
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What common thoracic radiographic sign may be see in cases of Cushing’s syndrome?
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Pulmonary mineralization is common.
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In what direction can a pituitary grow because it has an incomplete diaphragm sella?
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Dorsally.
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Which drug for the treatment of Cushing’s is a competitive inhibitor of cortisol?
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Trilostane (Mitotane causes necrosis of adrenal cortical tumors).
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In dogs with PDH eighty percent have a tumor of which part of the pituitary gland?
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Pars distalis (anterior lobe).
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Why do 50% of dogs with a macrotumor develop neurologic signs?
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Expansion into third ventricle or hypothalamus.
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What condition is caused by defective secretion or response to ADH?
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Diabetes insipidus.
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What is the cause of central diabetes insipidus?
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Defective production of ADH in the hypothalamus.
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What type of diabetes insipidus is caused by insensitivity of the renal tubules to ADH?
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Nephrogenic Diabetes insipidus.
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Pituitary hypoplasia typically presents as what clinical signs?
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Dwarfism.
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In which dog breed is pituitary hypoplasia a genetic defect?
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GSD.
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Why do dogs with pituitary hypoplasia have renal failure?
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Abnormal glomerular development due to lack of growth hormone.
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Epinephrine and norepinephrine is produced in what portion of the adrenal gland?
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The medulla.
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What do the three zone of the adrenal cortex produce?
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Glomerulosa produces aldosterone. Fasciculata is the glucocorticoids. Reticularis is sex steroids.
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What is the primary catecholamine produce by the adrenal gland?
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Epinephrine.
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Which cells produce Epinephrine and norepinephrine?
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Chromaffin cells.
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Which adrenergic receptors are in the heart?
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Beta 1 (Beta 2 is smooth muscle).
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What effects do Epinephrine and norepinephrine have on the heart?
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Increased heart rate and increased contraction.
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What effect does Epinephrine have on the respiratory system?
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Relaxation of bronchiolar smooth muscle via Beta 2 receptors.
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What is the main physiologic factor stimulating release of catecholamines?
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Hypoglycemia.
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What is the primary glucocorticoid released by the adrenal gland?
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Cortisol.
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What is the primary hormone influencing the release of glucocorticoids?
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ACTH.
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What are two main effects that glucocorticoids have on the liver?
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Gluconeogenesis. Glycogenolysis. (Redistributes fat to the liver).
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What effect does glucocorticoid have on inflammation?
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Inhibits synthesis of inflammatory mediators of arachidonic acid.
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What two conditions stimulate the release of renin?
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Decreased blood pressure and decreased sodium.
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What electrolyte condition stimulates the release of aldosterone?
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Hyperkalemia.
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If an adrenal cortical tumor is greater than 2 cm is likely what type?
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Adenocarcinoma
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Adenocarcinomas of the adrenal gland often invade which vessels?
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Renal vein. Caudal vena cava. Phrenicoabdominal.
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50% of adrenal carcinomas metastasize to where?
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Liver or the lung.
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What type of tumor is a functional malignancy of the adrenal Chromaffin cells?
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Pheochromocytoma.
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What is a paraganglionoma?
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Neoplastic extra adrenal pheochromocytoma.
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What percentage of pheochromocytomas create tumor thrombus?
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30-70%.
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Which neoplasia is the most common to spread to the adrenals in cats and dogs?
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Lymohoma.
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What percentage of adrenal function has to be lost before clinical signs of hypoadrenocorticism are seen?
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85%.
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What is thought to be the most common cause of hypoadrenocorticism?
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Immune-mediated adrenalitis.
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In which breed is Addison’s an inherited trait?
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Standard Poodle. Portuguese Water dog. Bearded Collie.
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What are the classic electrolyte abnormalities associated with hypoadrenocorticism?
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Hyponatremia and hyperkalemia (with non-regenerative anemia).
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What are possible radiographic signs of Addison’s?
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Hypovolemia (microcardia and small pulmonary vessels) +/- megaesophagus (from muscle weakness).
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What are the two possible causes of primary hyperaldosteronism?
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Aldosterone secreting tumor or bilateral adrenal hyperplasia.
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What causes secondary hyperaldosteronism?
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Renal disease.
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What are the classic electrolyte changes associated with hyperaldosteronism?
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Hypernatremia and hypokalemia.
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In which species does hyperaldosteronism tend to occur?
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10 yr+ cats.
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What is the most common clinical sign of hyperaldosteronism in cats?
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Ventroflexion of the neck and paresis and hindlimb weakness (secondary to hypokalemia).
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What is a common ultrasonographic finding of hyperaldosteronism?
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Adrenal mass.
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Which component of blood mediates adhesion of platelets to a damage vessel wall?
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Von Willebrand factor.
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In which disease condition are antibodies directed normal platelets?
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Immune-mediated thrombocytopenia.
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Which immunoglobulin is direct against the platelet membrane in ITP?
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IgG.
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Which dog breeds are over represented for ITP?
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Cocker spaniel. Poodle. Old English Sheepdog.
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What are the radiographic findings of ITP?
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Splenomegaly and hepatomegaly and signs of haemorrhage.
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Define anemia.?
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Reduction in rbc/Hb/Hct resulting in a decreased oxygen carrying capacity.
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What is the usual cause of IMHA in dogs?
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Idiopathic immune dysregulation.
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By which three methods does IMHA attack rbcs?
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Intravascular haemolysis. Intravascular agglutination. Removal by RES.
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What is the most common cause of death from IMHA?
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Thromboembolic disease included PTE.
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Which dog breed is at high risk fro IMHA?
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Cocker Spaniel.
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What are the common clinical signs of IMHA?
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Lethargy/depression/tachycardia/tachypnea.
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What is the concomitant condition of IMHA and ITP?
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Evan’s syndrome.
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What are the possible radiographic signs of IMHA?
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Hepatosplenomegaly +/- signs of PTE.
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In which congenital malformation is the viscera transposed?
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Situs inversus.
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Situs inversus may be associated with ciliary dyskinesis in what syndrome?
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Kartagener’s Syndrome.
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