Flashcards in Endocrinology - Hyperthyroidism Deck (50)
What is feline hyperthyroidism?
A multi-system disorder resulting from the overproduction and secretion of thyroid hormones
True or false: Feline hyperthyroidism is the most common endocrinopathy of cats.
Whatis the pathophysiology of hyperthyroidism?
Autonomous production of T4 from funcitonal thyroid tumors
What can cause hyperthyroidism in cats?
Benign multinodular adenomatous hyperplasia and/or thyroid adenomas (>95%) or thyroid carcinoma
What can cause hyperthyroidism in dogs?
What are the risk factors for hyperthyroidism (unless I mention otherwise, all questions are regarding cats)?
Canned food, variable iodine content and other dietary factors, age, use of cat litter, indoor housing, regular exposure to lawn and flea control products
True or False: Hyperthyroidism is likely multifactorial.
What is the signalment for hyperthyroidism?
Senior cats - 8 years or older (mean age is 13 years)
What historical clinical features are associated with hyperthyroidism?
Weight loss (>90%), polyphagia (80%), hyperactivity, vomiting, polydipsia/polyuria, hair coat changes, diarrhea/increased fecal volume, panting, and anorexia/hyporexia
What clinical features on PE are associated with hyperthyroidism?
From most to least common: palpable thyroid, thin, tachycardia, hyperactive/difficult to examine, heart murmur, skin changes, small kidneys, increased temperature, and gallop rhythm
How does hyperthyroidism affect the cardiovascular system?
Increase sympathetic tone and increased metabolic rate +/- systemic hypertension. It can cause hypertrophied cardiac muscle
On PE what physical exam findings will you find with hyperthyroidism?
Tachycardia, murmurs, and gallop rhythm
Since hypertension is an associated complication with hyperthyroidism, what must you do when you suspect hyperthyroidism?
evaluate the BP
How is hyperthyroidism diagnosed?
Consider signalment, history, and PE findings (palpate thyroid)
Consider clin path findings
Specific endocrine diagnostics
What specific endocrine diagnostics can be done for hyperthyroidism?
thyroid hormone concentrations, T3 suppression test, and thyroid scintigraphy
What will you find on CBC in hyperthyroid patients?
Mild erythrocytosis with a variably present stress leukogram
What will you find on serum biochemistry in patients with hyperthyroidism?
Elevated ALT and/or ALP and variably present azotemia
Why can hyperthyroidism mask underlying disease?
Because it increases renal blood flow
What will you find on UA in a patient with hyperthyroidism?
variable USG and proteinuria
True or False: A majority of cats with hyperthyroidism will have a high total T4.
Is a high TT4 diagnostic?
Yes - typically it is safe to assume that if a cat has an elevated TT4 then it is hyperthyroid
Does a normal TT4 rule out hyperthyroidism?
No, cats with early or mild hyperthyroidism will have a normal TT4 therefore one TT4 within the referencerange does not rule it out
If hyperthyroidism is suspected but TT4 is normal, what can be done?
Recheck in 3-6 weeks or use additional diagnostics such as fT4ed, T3 suppression test, or thyroid scintigraphy
What does a fT4ed measure?
free, unbound fraction of thyroid hormone
What is a fT4ed sensitive diagnostic for?
Since fT4ed is sensitive for diagnosing hyperthyroidism, is it diagnostic as a stand alone test in cats?
no - it should not be used as a stand alone
When is a T3 suppression test indicated?
To confirm diagnosis when clinical suspicion of hyperthyroidism and high-normal TT4
In nnormal cats, what will the T4 level be during the T3 suppression test?
T4 will fall tp <50% of pre-levels
In hyperthyroid cats, what will happen during a T3 suppression test?
There will be minimal suppression