Lecture 13 3/27/25 Flashcards
(41 cards)
What are the characteristics of feline hyperthyroidism?
-most common feline endocrine disorder
-commonly seen in GP
What are the characteristics of feline hyperthyroidism pathophysiology?
-thyroid adenomatous hyperplasia
-foci and nodules of hyperplastic tissue
-multiple, bilateral, benign masses are most common
-occasionally ectopic
-malignant carcinoma is rare
What are the suspected roles of genetics in feline hyperthyroidism risk?
-decreased risk seen in siamese and himalayan cats
-increased risk seen in non-purebred cats
-decreases in G inhibitory proteins lead to increased stimulation of growth
What are the suspected environmental risk factors for feline hyperthyroidism?
-canned food with pop top lids
-iodine
-BPA and phthalates
-flame retardant PBDEs
-other goitrogens
What is the signalment for feline hyperthyroidism?
-middle to older age cats; typically > 10 yrs
-any breed
-any gender
What are the most common clinical signs of feline hyperthyroidism?
-weight loss (most common)
-vomiting
-PU/PD
-hyperactivity/restlessness
-diarrhea
What are other potential clinical signs of feline hyperthyroidism?
-anorexia
-lethargy
-tremors/weakness
-dyspnea/panting
-heat and stress intolerance
-thyroid storm
What is thyroid storm?
rare, life-threatening secondary rapid T4 increase
Why is it important to palpate the entire cervical region in cats with suspected hyperthyroidism?
many cats with have palpable thyroid nodules
What are other findings on physical exam besides a palpable nodule in cats with hyperthyroidism?
-cachexia/thin body condition
-tachycardia
-systolic murmur
-arrhythmia
-effusion
-edema
-fundic abnormalities
-abnormal blood pressure
Which cardiac diseases can be seen with hyperthyroidism?
-reversible hypertrophy secondary to hyperthyroidism
-concurrent primary hypertrophic cardiomyopathy
What should be included in the diagnostic workup of a suspected hyperthyroid cat?
-CBC/chem/UA
-thyroid hormone screening
-BP measurement
-thoracic rads
-ECG
-echo
-possibly additional imaging
-evaluation of other conditions
What are the findings on chem in hyperthyroid cats?
-elevated hepatic enzymes, esp. ALT
-reversible, mild to moderate enzyme elevations
-stress hyperglycemia
-possible azotemia
-possible hyperphosphatemia
What are the findings on UA in hyperthyroid cats?
-decreased USG
-possible/asymptomatic UTI secondary to decreased host defenses
What are the characteristics of hyperthyroidism and the kidneys?
-older cats often have decreased kidney function or CKD
-hyperthyroid state increases renal blood flow and enhances GFR
-renal failure can be masked by the hyperthyroid state
How does survival rate differ between cats with concurrent hyperthyroidism and kidney disease vs cats with just hyperthyroidism?
cats with both conditions do not live as long
Which diagnostics are done to assess the cardiovascular system in hyperthyroid patients?
-radiographs
-ECG and/or echo
-BP measurements
What findings can be seen on thoracic rads in hyperthyroidism patients?
-more prominent cardiac silhouette
-heart failure
-lung nodules
How is feline hyperthyroidism diagnosed?
single elevated serum TT4 is diagnostic
What are the limitations of TT4 measurement?
-daily and hourly fluctuations
-can be normal in early or mild hyperthyroidism cases
-can be depressed by non-thyroidal illness
How should increased fT4 be interpreted, based on TT4 measurement?
-low to low-normal TT4 with increased fT4: non-thyroidal illness
-high-normal to high TT4 with increased fT4: hyperthyroidism
What are the characteristics of the T3 suppression test?
-administer T3 and measure T3 and T4 (and possibly TSH)
-normal cats should have low TSH and T4 due to negative feedback
-hyperthyroid cats will have minimal decreases in T4
What are the characteristics of TSH measurement?
-feline TSH can be measured with canine kits
-not routinely done
-often reserved for challenging cases
What are the characteristics of thyroid scintigraphy?
-radioactive marker identifies functional thyroid tissue
-confirms diagnosis of hyperthyroidism
-can detect unilateral vs bilateral, benign vs malignant, ectopic, and metastatic dz
-used prior to radioiodine treatment to plan dosing