2/3 Thyroid Hormones - Hyperthyroidism COMPLETE *** Flashcards
Hyperthyroidism: Which species is this common in?
- Why species is this less common in?
cats
dogs
Hyperthyroidism: What is hyperthyroidism?
- What causes it?
excessive production of thyroxine
adenomatous hyperplasia of the thyroid gland
Hyperthyroidism: What is the consequence of having excess T4 on basal metabolic rate? 2
increased metabolic rate
so increased catabolism of stores
Hyperthyroidism: Aside from basal metabolic rate, what does increased T4 effect? 3
thermoregulation
emetics centre
increases sympathetic drive
Hyperthyroidism: What are some potential risk factors for developing the disease? 3
flea products
cat litter
food containing high iodine
Hyperthyroidism: Signalment 2
cats older than 10
rare in siamese cats
Hyperthyroidism: List the clinical signs from most common to least common 7
weight loss
polyphagia
polyuria and polydipsia
tachycardia
vomiting
diarrhoea
hair coat changes
Hyperthyroidism: Why do we get weight loss and polyphagia?
because T4 increases metabolic rate and catabolism
Hyperthyroidism: Why do we get PU/PD?
increased cardiac output increasing glomerular filtration rate
Hyperthyroidism: Why do we get tachycardia?
increased sympathetic drive
Hyperthyroidism: Why do we get vomiting? 2
due to overeating
due to activation of the emetics centre
Hyperthyroidism: why do we get diarrhoea?
due to hyper mobility of the gastrointestinal tract and malabsorption
Hyperthyroidism: Why might we get hair coat changes?
the cat may forget to groom or overgroom
Hyperthyroidism: What might you pick up on clinical examination? 4
poor body condition
cervical nodule
tachycardia
other cardiac abnormalities
Hyperthyroidism: Aside from Tachycardia, what other cardiac abnormalities could be present? 2
hypertrophic cardiomyopathy
systolic murmur
Hyperthyroidism: What happens in scintigraphy?
radioactive 123 idoine isotope is administered to identify functional thyroid tissue
Hyperthyroidism: Diagnosis
- Which test is sufficient for diagnosis of Hyperthyroidism?
- Why do we sometimes only need to do this one?
- What are the only problems? 3
- Hence, which test would be better the perform if possible and why?
total t4
because there is no other reason for T4 to be elevated
there are daily fluctuations
it may be within normal parameters in early-mid hyperthyroidism
could be depressed by non-thyroidal illnesses
free T4 as it is less affected by non-thyroidal illnesses
Hyperthyroidism: State 3 other diagnostic tests that could be done, although often dont need to be done outside of Total/Free T4?
T3 suppression test
TRH stimulation test
scintigraphy
Hyperthyroidism: Describe the procedure for carrying out a T3 suppression test 2
- Why do we test for both T4 and T3?
- In a normal cat, what would be the result and why?
- what would you see in a Hyperthyroid cat?
administer a tablet containing T3
measure blood T4 and T3
to check owner compliance
T4 concentration would be significantly reduced due to negative feedback from exogenous T3
minimal decrease in T4 concentration
Hyperthyroidism: Treatment
- State 4 ways of treating Hyperthyroidism
inhibitors of thyroid hormone synthesis
surgical removal of enlarge thyroid gland
radiotherapy to destroy local thyroid tissue
dietary control
Hyperthyroidism: Treatment
- What does ‘dietary control’ involve?
exclusively feeding a diet that is deficient in iodine and selenium
