Thyroid Hormones & Anti-Thyroid Drugs

Question 1

what’s the active form of thyroid hormone?

Answer 1

T3
since changes in gene expression

Question 2

thyroid hormones increase stim sensitivity of…

Answer 2

sympathetics

Question 3

hypothyroid diagnostics will show ___ T4 and ___ TSH

Answer 3

decreased T4
increased TSH

Question 4

do hypothyroid pts have more parasympathetics or sympathetics?

Answer 4

parasympathetic tone
since lacking hormone

Question 5

hyperthyroid diagnostics will show ___ T4 and ___ TSH

Answer 5

increased T4
decreased TSH

Question 6

do hyperthyroid pts have more parasympathetics or sympathetics?

Answer 6

sympathetics

Question 7

describe primary hypothyroidism

Answer 7

commonly due to lymphocytic thyroiditis (increased circulating anti-thyroglobulin Ab)
rarely congenital

Question 8

what drugs cause drug induced hypothyroidism?

Answer 8

Trimethoprim/Sulfonamide
Glucocorticoids
Phenobarbitol

Question 9

Levothyroxine indications

Answer 9

Tx hypothyroidism
dog, cat, horse, bird, reptile

Question 10

Levothyroxine should be given before ___ to avoid ___ bioavailability

Answer 10

before breakfast
decreased bioavailability

Question 11

Levothyroxine liquid dose is ___ the amount of pill dose

Answer 11

liquid is 1/2 the pill dose

Question 12

Levothyroxine metabolism

Answer 12

hepatic, needs glucouronidation

Question 13

Levothyroxine adverse effects

Answer 13

iatrogenic hyperthyroidism, thyrotoxicosis - due to giving too much
***be sure to monitor T4 for good dose

Question 14

Levothyroxine contraindications

Answer 14

thyrotoxicosis
acute myocardial infarction (heart attack, increase T4 causes increase CO)
untreated adrenal insufficiency - since adrenal and T4 work together

Question 15

hyperthyroidism is more common in what species?

Answer 15

cats&raquo_space; dogs

Question 16

what is hyperthyroidism caused by?

Answer 16

adenomatous hyperplasia of thyroid (increased follicles)
altered signaling sensitivity to TSH
active adenocarcinoma
HIGH levels of iodine

Question 17

what can be an overlapping pathology of hyperthyroidism?

Answer 17

chronic kidney failure (CKD)
increased CO -> increased kidney blood flow -> increased GFR -> masks low GFR of CKD

Question 18

Methimazole indications

Answer 18

Tx hyperthyroidism

Question 19

Methimazole administration and efficacy

Answer 19

PO - 90%
transdermal - 60%

Question 20

Methimazole concentrates where?

Answer 20

thyroid colloid

Question 21

Methimazole is a ___ acting drug

Answer 21

slow
takes 3-4 weeks for T4 to normalize

Question 22

Methimazole adverse effects

Answer 22

unmasks cryptic CKD
forms ati-nuclear Ab, can lead to myasthenia syndrome
self induced excoriation (scratching)

Question 23

how do you reverse Methimazole adverse effects?

Answer 23

stopping drug
takes about 1 month to return to normal

Question 24

radioactive Iodine 131 indications

Answer 24

Tx hyperthyroidism by killing follicle cells of thyroid

Question 25

radioactive Iodine 131 administration protocol

Answer 25

single dose, concentrates in colloid
pt must stay in clinic until all iodine is out of body

Question 26

radioactive Iodine 131 is a ___ Tx

Answer 26

irreversible

Question 27

radioactive Iodine 131 kills ___ cells, not ___ cells in thyroid

Answer 27

kills follicle cells NOT C-cells
***NO Ca effect

Question 28

which drug would you use to test a pt’s kidney function prior to long term Tx of hyperthyroidism: radioactive Iodine 131 or Methimazole?

Answer 28

Methimazole

Question 29

list signs of thyrotoxicosis

Answer 29

tachycardia
hypertension
tachypnea
hypokalemia
venous thromboembolism
seizure

Question 30

describe Propanolol usage for thyrotoxicosis

Answer 30

B1/2 antagonist
decreases HR
promotes T4 conversion to reverse T3