Thyroid

Question 1

Describe the structure of thyroid hormones

Answer 1

2 tyrosine molecules stuck together

Question 2

half lives of T4? T3?

Answer 2

T4: 7 days
T3: 1 day

Question 3

Hashimoto’s thyroiditis

Answer 3

• an autoimmune disease caused by antibodies made against thyroid peroxidase and/or thyrogloculin that gradually destroy the thyroid gland follicles
• often misdiagnosed as depression or anxiety,, and sometimes even bipolar disorder

Question 4

What are some hypothyroidism tx precautions?

Answer 4

• thyroid hormones increase adrenergic receptor sensitivity to catecholamines
• for all practical purposes, thyroid hormones do not cross the placenta in clinically meaningful amnts

Question 5

describe hypothyroidism Tx

Answer 5

• if due to iodine deficiency, then add iodine to the diet (elderly, poverty)
• for gland failure, levothyroxine (T4) is the treatment of choice
• body will convert T4 into T3 as required

Question 6

What is graves disease?

Answer 6

• the most common form of hyperthyroidism

- activating Ab to TSH receptor. Leads to increased T3 and T4 levels

Question 7

What iodine isotope is used for thyroid treatment? How does it work?

Answer 7

• isotope: 131^I
• this is the Tx of choice by many centres
• ionizing radiation destroys the gland
• caution with other anti-thyroid drugs as must be concentrated into uptake gland
• CI in pregnancy and children

Question 8

Describe thoamide drugs

Answer 8

MOA:

• block synthesis of thyroid hormones
• interferes with organification of iodine; a competitive inhibitor of peroxidase
• blocks MIT conversion to DIT
• Inhibits couping of iodinated tyrosines
• they do NOT affect uptake of iodide or T4/T3 release

Question 9

Propylthiocuracil, a thioamide drug, has what MOA

Answer 9

inhibits conversion of T4 to T3

Question 10

List two thioamide drugs. Which is preferred in pregnancy?

Answer 10

• propylthiouracil (PTU) *preggo preferred

- Methimazole

Question 11

What are some cautions to note when using thioamide drugs?

Answer 11

• most common side effect is leukopenia (low WBC count)
• WBC status changes with thyroid status. Therefore, routine monitoring not recommended. Stop drug therapy at first sign of sore throat and/or fever, then determine WBC status

Question 12

What are adrenergic side effects of thyroid hormones?

Answer 12

• SOB
• anxiety
• sweating
• tachycardia
• chest pain
• MI **

Question 13

propanolol use in hyperthyroidism???

Answer 13

ameliorates CV symptoms/toxicity and allows for some suppression of T4 to T3 conversion