LEC 2 - Thyroid Hormones + Anti-Thyroid Hormones

Question 1

What are the two hormones that the thyroid release?

Answer 1

T4/T3

Calcitionin

Question 2

What cells release T4/T3?

Answer 2

Follicle cells

Question 3

What cells release calcitonin?

Answer 3

C Cells

Question 4

What is the process by which T4/T3 get into the blood stream?

Answer 4

Iodine comes from blood via Na+ channel then pendrin

Thyroid peroxidase puts I- onto thyroglobulin

Carries T3/T4 into cytoplasm

Broken down by lysosome

Question 5

What are the neuroendocrine effects of TH?

Answer 5

Increased sensitivity of SNS stimulation

Increased stimulation of all other endocrine organs

Question 6

What are the cardiac effects of TH?

Answer 6

Increased CO

via HR + contractility + BP

Question 7

What are the respiratory/metabolic effects of TH?

Answer 7

Increased O2 + energy consumption

Increased erythropoiesis leading to O2 delivery

Question 8

What are the regulatory hormones of the thryoid?

Answer 8

TRH

– and –

TSH

Question 9

Diagnostics: Hypothyroid

Answer 9

decreased T4

Increased TSH

Question 10

Diagnostics: Hyperthyroid

Answer 10

Increased T4

Decreased TSH

Question 11

What are the four effects of TSH?

Answer 11

Stimulate Iodine symport (NIS)

Activates thyroglobulin synthesis

Activates throid peroxidase

Stimulates lysosomal breakdown of Thyroglobulin

Question 12

What are the signs a dog is hypothyroid?

Answer 12

Alopecia

Lethargy

Overall sad appearance

Question 13

What are the four major reasons for hypothryoidism?

Answer 13

Lymphocytic thyroiditis

Congenital

Nutritional status/Underlying disease

Drug-induced

Question 14

What drugs can induce hypothyroidism?

Answer 14

Trimehtoprim/sulfonamides

Glucocorticoids

Phenobarbital

Question 15

Which of the drugs that cause hypothyroidism cause there to actually be clinical symptoms?

Answer 15

Trimethoprim/sulfonamides

Question 16

What is the drug for hypothyroid?

Answer 16

Levothyroixine

Question 17

How is levo absorped/given?

Answer 17

Orally

Bioavaliblity decreased with food

Question 18

How is levo handled in the body?

Answer 18

Most bound to plasma protein

Question 19

How is levo metabolized?

Answer 19

Hepativ

Glucoronnylation

Sulfation

Deamination

Question 20

What are the contrindications for levo?

Answer 20

Thyrotoxicosis

Acute myocardial infarction

Untreated adrenal insufficency

Question 21

What are the adverse side effects of levo?

Answer 21

Iatrogenic hyperthyroidism

erythema multiforme

Question 22

What are the signs of hyperthryoid in a cat?

Answer 22

Weight loss with atrophy

PU/PD

Hyperactive

Can feel thyroid lobes

Question 23

What can cause adenomatous hyperplasia of the thyroid?

Answer 23

Associated with altered signaling sensivity to TSH

High levels of dietary Iodine/soy may be the cause

Question 24

When starting to treat a cat with hyperthyroid what is important to remember?

Answer 24

Unmasking CKD in older cats

Increased CO leads to better perfusion of the kidneys, therefor increased GFR

Question 25

What are the signs of renal failure?

Answer 25

Increased:

Creatinine

BUN

Question 26

What is the drug of choice for hyperthyroid? Where does it work?

Answer 26

Methimazole

Inhibits production of Thyroid peroxidase

Inhibits binding of T4/T3 to Thyroglobulin

Question 27

How is methimazole given?

Answer 27

PO

or

Transdermally

Question 28

What are the adverse effects of methimazole?

Answer 28

Unmasking CKD

Forming anti-nuclear bodies

Vomiting/Lethargy

Thrombocytopenia/Leukopenia

Hepatopathy

Question 29

What should be done if you are seeing GI effects of methimazole?

Answer 29

Give transdermally

Question 30

What is the rate at which methimazole works?

Answer 30

SLOW

takes 3 to 4 weeks to normalize T4 levels

Question 31

How is I¹³¹ used?

Answer 31

Irreversible treatment of hyperthryoid

Destroys the cells but aren’t powerful enough to destroy C cells