Lecture 19 Lecture Capture Only Flashcards
(20 cards)
What are the characteristics of thyroid gland anatomy and physiology?
-follicles are filled with colloid
-follicular epithelium converts colloid into T3/T4
-C-cells make calcitonin
What is the pathogenesis of goiter?
-impaired T4 production
-increased TSH due to low thyroid hormones
-thyroid hyperplasia
What can impair T4 production?
-iodine-deficient diet
-goiterogenic substances that interfere with Tg/T4 production
-inherited enzymatic defects
What are the underlying lesions of canine hypothyroidism?
-lymphocytic thyroiditis
-idiopathic atrophy
What are the consequences of hypothyroidism?
-gain in body weight w/o changes in appetite
-bilaterally symmetrical alopecia and scaly skin
-atherosclerosis from hypercholesterolemia
-myxedema
What are the types of neoplasia that affect the thyroid glands?
-adenomatous hyperplasia/adenoma in cats
-carcinoma in dogs
-adenoma in horses
What are the characteristics of feline hyperthyroidism?
-old cats
-typically due to adenomatous hyperplasia/adenoma
-carcinoma possible but rare
-majority of cats have bilateral lesions
What are the consequences of hyperthyroidism?
-hypertension
-hyphema
-retinal detachment
-cardiac hypertrophy
What are the characteristics of canine thyroid carcinoma?
-usually non-functional
-usually follicular
-unilateral
-aggressive malignancy
What are the characteristics of equine thyroid adenomas?
-usually non-functional and an incidental finding
-C-cells > follicular
-often multifocal
What are the characteristics of parathyroid gland anatomy and physiology?
-two paired glands
-produce parathyroid hormone in response to low blood calcium
-inhibited by vitamin D
What are the characteristics of parathyroid gland hyperplasia?
-underlies secondary hyperparathyroidism
-all glands enlarged
What are the possible pathogeneses of parathyroid gland hyperplasia?
*nutritional
-low vitamin D
-low Ca/high P
*renal
-low vitamin D
-high P
What are the characteristics of fibrous osteodystrophy?
-consequence of secondary hyperparathyroidism
-PTH stimulates increased resorption of bone
-chronic PTH also stimulates bone marrow stromal cells to differentiate into fibroblasts
-high P and low vitamin D leads to low Calcium and the inability to properly mineralize growing bone
What are the characteristics of parathyroid adenoma?
-underlies primary hyperparathyroidism
-rare
-one gland enlarged
-main consequence is hypercalcemia
What are the characteristics of humoral hypercalcemia of malignancy?
-“pseudohyperparathyroidism”
-caused by PTHrp produced by tumors
-associated with lymphoma and AGASACA
-consequence is hypercalcemia
-parathyroid glands often atrophy over time
What are the hormones produced by the pancreatic islet cells?
-alpha cells: glucagon
-beta cells: insulin
-delta cells: somatostatin
What are the characteristics of pancreatic islet degeneration/atrophy?
*may underly diabetes mellitus
*T1D is insulin-dependent DM
-islets are destroyed and lost
-no insulin is made
*T2D is non-insulin dependent DM
-common in obese cats
-insulin is made but antagonized
-no lesions in pancreatic islets
What are the consequences of diabetes mellitus?
-fatty liver
-atherosclerosis
-cataracts
-microangiopathy
-lesions caused by infections and impaired leukocyte function
What are the characteristics of pancreatic islet neoplasia?
-can be pancreatic islet adenoma or carcinoma
-most common are “insulinomas” derived from beta cells
-typically multiple insulinomas
-common in dogs (malignant) and ferrets (benign)
-leads to hypoglycemia and nonspecific neuro signs
