Thyroid Gland Flashcards
What are the 3 forms of thyroid hormones and which is the most active?
T3, T4 and Reverse T3
T4 is less biologically active but more abundant
At the target cell T_ is converted to T_ and ___
4
T3 and rT3
What are conditions associated with decreased tT4?
Primary hypothyroidism
Euthyroid sick syndrome
What is a condition associated with increased tT4?
Hyperthyroidism; Feline thyroid adenoma
What condition is associated with decreased fT4?
Primary hypothyroidism
ESS: rarely see decreased fT4
What condition is associated with increased fT4?
Hyperthyroidism; feline thyroid adenoma
T/F tT3 and fT3 can be used and have good diagnostic utility
FALSE
Endogenous TSH comes from _____
pituitary gland
A _____ in tT4 and an _____ in TSH is supportive of hypothyroidism
Increase in tT4
Decrease in TSH
TSH stimulation tests looks at what?
Thyroid gland’s ability to respond to TSH to produce T4
A TSH stim test would get what result in a hypothyroid dog? What about normal dog?
Hypothyroid: No response
Normal/ESS: Increase tT4 post TSH stimulation
TRH stimulation test looks at what?
Pituitary’s response to TRH to produce TSH
What results would you see with a TRH stimulation test?
Hypothyroid: No increase in tT4
Normal/ESS: increase in tT4 following stim
T3 suppression test is useful for what disease?
Feline hyperthyroidism
What response would you see in a hyperthyroid cat to a T3 suppression test?
No decrease in tT4 after the T3 administration
What is the most common form of canine hypothyroidism?
Primary (At the level of the thyroid)
What are some common lab abnormalaties seen with canine hypothyroidism?
Hyperlipidemia
Increased ALP, GGT, and AST
Mild anemia
Euthyroid sick syndrome is what?
Non-thyroidal disease that suppresses plasma T4
Total T4 test would be helpful to rule ___ hypothyroidism
OUT; most hypothyroid dogs have decreased total T4
T/F Euthyroid sick syndrome dogs will have decreased total T4
TRUE
T/F Most Euthyroid sick syndrome dogs have decreased free T4
FALSE; most of these have normal fT4
Hypothyroidism dogs will have ____ fT4
Decreased
What is the best one-measurement test for diagnosing canine hypothyroidism?
Free T4 by equilibrium dialysis
What other test could you use to test a hypothyroid dog to DDx from EES?
Endogenous TSH
Hypo: Increased TSH w/ decreased tT4
EES: normal TSH
