Lecture 23 4/8/25 Flashcards by Danika Boltz

What is the anatomy of the canine thyroid gland?

-two lobes that produce thyroid hormones
-parathyroid glands
-closely associated with carotid arteries, larynx, recurrent laryngeal nerve, trachea, and esophagus

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Where can ectopic thyroid tissue be found?

-base of tongue
-basiohyoid
-cranial mediastinal
-heart base

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Which lymph nodes can the thyroid gland drain to?

-submandibular
-retropharyngeal
-superficial/deep cervical (prescapular)

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What are the possibilities for thyroid tumors?

-can be a benign adenoma, but very rare
-if palpable, typically malignant
-most common malignancy is carcinoma

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What is the typical signalment for canine thyroid carcinoma?

-older, medium to large breeds
-genetic predisposition
-most common in boxers, huskies, golden retrievers, and beagles

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What are the characteristics of canine thyroid carcinoma?

-locally invasive
-moderate metastatic potential; more likely to occur with large tumor size or bilateral involvement
-metastasizes to lymph nodes and lungs
-slowly progressive

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What are the clinical signs of canine thyroid carcinoma?

-palpable ventral cervical mass
*if large/invasive:
-coughing/tachypnea/dyspnea
-dysphonia
-dysphagia
-laryngeal paralysis
-horner’s syndrome
*if functional (rare):
-polyphagia
-weight loss
-PUPD

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What are the characteristics of functional thyroid carcinomas?

-tumor functions like thyroid tissue and produces thyroid hormones
-rare in dogs, more common in cats

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What should be done on physical exam when assessing a thyroid tumor?

-determine if mass is freely moveable or fixed
-palpate and FNA the regional lymph nodes

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What are the characteristics of cytology as a diagnostic for thyroid tumors?

-can identify neuroendocrine neoplasm
-may be non-diagnostic
-cannot determine malignant vs benign

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What are the characteristics of histopathology as a diagnostic for thyroid tumors?

-gold standard
-must do excisional biopsy
-incisional biopsy has too high of a hemorrhage risk

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What are the diagnostics done for patients with thyroid tumors?

-CBC/chem/UA (often normal)
-thyroid panel (often normal)
-cytology of lymph nodes
-three-view thoracic rads
-cervical ultrasound
-CT scan

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What are the characteristics of the thyroid panel result breakdown in dogs?

-60% of patients with thyroid tumors are euthyroid
-30% are hypothyroid
-10% are hyperthyroid

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Why is it important to know how dogs with thyroid tumors typically present on thyroid panel?

-functional tumors that make the dog hyperthyroid are rare
-condition is more common in cats

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What are the characteristics of surgery as a treatment for thyroid tumors?

-done for “freely moveable” tumors
-can be curative if no metastatic dz
-MST of around 3 years
-side effects include hemorrhage and damage to recurrent laryngeal n.

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What are the characteristics of radiation as a treatment for thyroid tumors?

-definitive radiation for fixed or invasive tumors with an MST of 3 years
-palliative radiation for local mass with metastatic dz with an MST of 1 year
-takes months to over a year to see maximal response

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What are the characteristics of chemo as a treatment for thyroid tumors?

-no proven benefit for microscopic dz
-palladia can be used in animals with gross or metastatic dz

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What are the characteristics of radioactive iodine as a treatment for thyroid tumors?

-will treat metastatic dz
-must use higher doses than in cats
-limited availability
-requires isolation
-causes myelosuppression

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What are the characteristics of adrenal gland anatomy?

-occur near the kidneys
-closely associated with phrenicoabdominal vein and vena cava

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What are the characteristics of adrenal gland tumors?

-common in dogs, uncommon in cats
-typically occur in adrenal cortex
-locally invasive
-metastasis uncommon

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What are the 4 classifications of adrenal tumors?

-functional
-non-functional
-benign
-malignant

What can cause clinical signs from functional tumors?

-excessive cortisol production in dogs
-excessive aldosterone production in cats
-excessive catecholamine production in dogs

What are the characteristics of adrenal-dependent hyperadrenocorticism?

-most common functional adrenocortical tumor in dogs
-results in cortisol excess
-seen in poodles, german shepherds, dachshunds, and labs
-diagnosed via LDDST

What are the characteristics of aldosterone?

-stimulated by low blood pressure or high potassium
-goal is to increase blood volume and lower potassium
-leads to sodium reabsorption and potassium excretion in the urine

What are the characteristics of primary hyperaldosteronism/Conn's syndrome in cats?

-symptoms include hypokalemia, increased blood vol., and high blood pressure -muscle weakness due to low potassium -increased serum sodium levels -decreased plasma renin levels -increased fluid vol. can cause loss of sodium and water -treatment via aldosterone antagonists

What is the #1 adrenal tumor in cats?

primary hyperaldosteronism/Conn's syndrome

What are the consequences of profound hypokalemia in Conn's syndrome?

-muscle weakness -cervical ventroflexion -dysphagia

What are the consequences of systemic hypertension in Conn's syndrome?

-retinal detachment -myocardial hypertrophy -renal disease

How is Conn's syndrome diagnosed?

-increased or normal aldosterone levels despite low potassium -possible finding of adrenal mass

What are the characteristics of pheochromocytoma?

-intermittent secretion of catecholamines -pulsatile secretion; clinical signs come and go -leads to metanephrines and normetanephrine in the urine

What are the clinical signs of pheochromocytoma?

-weakness -collapse -arrhythmias -hypertension -tachycardia -tachypnea

Which tests are used for diagnosis and staging of adrenal tumors?

-CBC/chem/UA -blood pressure -three-view thoracic rads -abdominal ultrasound -abdominal CT -endocrine testing

What are the characteristics of surgery as a treatment for adrenal tumors?

-adrenalectomy is treatment of choice -functional tumors may need medical therapy prior to surgery -can be curative; MST of 4 years

Which medications are used for medical treatment of pheochromocytoma?

-phenoxybenzamine or prazosin

Which medications are used for medical treatment of cortisol-secreting adrenal tumors (ADH)?

-trilostane -mitotane

Which medications are used for medical treatment of aldosterone-secreting adrenal tumors (Conn's)?

-potassium supplementation -amlodipine -spironolactone

When is medical treatment of adrenal tumors done?

-prior to surgery for functional tumors -inoperable masses -patients with concurrent disease

What is the approach to an incidentaloma/adrenal tumor with no presenting signs?

-determine if the tumor is functional -determine if there are indications for surgery or indications for monitoring

What are the indications for surgery for incidentalomas?

-functional tumor -size larger than 2.5 cm -vascular invasion

What are the indications for monitoring for incidentalomas?

-non-functional -small -non-invasive

What are the characteristics of pancreas anatomy?

-situated near stomach and duodenum -exocrine cells produce digestive enzymes -endocrine cells/beta cells produce insulin

What are the characteristics of insulinoma?

-tumor of pancreatic beta cells -autonomous insulin secretion -locally invasive -highly metastatic; goes to liver, lymph nodes, and lungs

What are the clinical signs of insulinoma?

*intermittent signs that worsen with exercise or fasting -weakness -lethargy -ataxia -collapse -disorientation -behavioral changes -seizures

How are insulinomas staged?

-CBC/chem/UA -3-view thoracic rads -abdominal ultrasound -abdominal CT

What are the characteristics of insulinoma diagnosis?

-confirm diagnosis with insulin:glucose ratio -test is only valid when BG < 60 mg/dL -normally, if BG is low insulin is low -abnormal findings are normal to high insulin when BG is low -abnormal insulin:glucose ratio warrants ex-lap even if imaging does not find pancreatic mass

What are the characteristics of surgery as an insulinoma treatment?

-treatment of choice -remove pancreatic mass and debulk any mets if possible -biopsy anything abnormal -complications include hypoglycemia, diabetes mellitus, and pancreatitis

What is the standard medical treatment for insulinoma?

-small, frequent meals -avoid strenuous exercise and excitement -prednisone -medications to decrease insulin secretion like diazoxide or octreotide *goal is to resolve clinical signs, not necessarily reach euglycemia*

What are the characteristics of palladia chemo for insulinoma?

-used in cases of metastatic dz or recurrent hypoglycemia -partial response or stable disease in addition to symptomatic relief -improved survival vs medical management alone

What are the characteristics of streptozotocin chemo for insulinoma?

-not widely used -lots of side effect; highly emetogenic and nephrotoxic -kills pancreatic beta cells; can lead to diabetes mellitus

What is the prognosis for insulinoma?

-variable depending on extent of disease -surgery +/- medical therapy has longer survival than medication alone -palladia has increased survival times

What are the stages for insulinoma?

stage 1: pancreas only stage 2: pancreas + lymph node stage 3: pancreas + liver or other distant metastasis + lymph node