Thyroid Gland

Question 1

Druh of choice in myxedema and cretinism. GR: T3 is added to it.

Answer 1

Levothroxine (eltroxine)
To avoid polymorphism in D2 enzyme

Question 2

Which member of thionamides is preferred and why?

Answer 2

Methimazole
Given once daily, less side effects

Question 3

Describe mechanism of action of thionamides

Answer 3

1. Prevent thyroid hormone synthesis by inhibiting iodide oxidation, organification, couplinh of MIT & DIT
2. PTU: inhibit periphernal conversion of T4 to T4 (deiodinase enzyme)

Question 4

List uses of ATDs

Answer 4

1. Hyperthyroidism: 1-2 yrs
2. Preparation for subtotal thyroidectomy, till euthyroid
3. Reduce thyrotoxic symptoms while waiting for radioactive iodine to act
4. Thyrotoxic crisis (PTU)

Question 5

List adverse effects of ATDs

Answer 5

1. Maculopapular rash & arthralgia (most common)
2. Agranulocytosis (most serious)
3. Hepatic necrosis (PTU) & cholestatic jaundice
4. Fetal goitre (MMI)

Question 6

Describe treatment of hyperthyroidism during pregnancy

Answer 6

1. PTU during 1st trimester
2. MMI during 2nd & 3rd trimesters

Question 7

List pharmacological actions of high dose iodine

Answer 7

1. Inhibit organification
2. Inhibit release of thyroid hormones by inhibiting proteolysis
3. Dec size & vascularity of hyperplastic gland

Question 8

Iodine loses its effectiveness after…..
Explain

Answer 8

2 weeks
Due to compensatory inc in TSH leading to T3/T4 release with loss of iodine effect

Question 9

List indications of iodine

Answer 9

Thyrotoxic crisis
Preoaration fir thyroidectomy

Question 10

Describe mechanism of action of radioactive iodine

Answer 10

1. Oral I(131) is rapidly absorbed & concentrated in thyroid gland
2. Emits b-rays with poor penetration causing severe damage of thyroid gland without damaging other tissues

Question 11

Indications & CI of radioactive iodine

Answer 11

Hyperthyroidism in patients over 45, not fit for surgery or having recurrence after surgery
CI: young, pregnant lactating (genetic damage & cancer)

Question 12

Adverse reactions of radioactive iodine

Answer 12

1. Hypothyroidism
2. Recurrence
3. Radiation thyroiditis: inc release of thyroid hormones with cardiac complications avoided by pretreatment with ATDs

Question 13

Describe mechanism of action & indications

Answer 13

1. Antagonizes sympathetic overactivity in thyrotoxicosis
2. Inhibit T4 to T3 conversion
   Ind:
3. Symptomatic relief of sympathetic overactivity in thyrotoxicosis
4. Storm of thyrotoxicosis
5. Surgery before thyroidectomy

Question 14

Describe treatment of thyrotoxic crisis

Answer 14

1. Propranolol
2. PTU
3. Iodides after 1-2 hrs
4. Hyrocortisone inhibit T4-T3 conversion + adrenal support
5. Lithium if patient allergic to iodides/PTU
6. Correct fluid balance & hyperthermia, treat HF, arrhythmia
7. Plasmaphersis & peritoineal dialysis in resistant cases

Question 15

List steps of preparation for thyroidectomy

Answer 15

1. ATD till euthyroid (6 weeks)
2. BBs
3. K iodide 15 days before surgery (dec size & vascularity)
4. Thyroid supplements after operation