Pharm 2 Thyroid

Question 1

Thyroid feedback

Answer 1

1. T3/4 reduce TRH receptor number

2. T3/4 inhibit hypothalamus -> TRH

Question 2

Thyrotropin (TSH) subunits

Answer 2

a - identical to LH, FSH, CG

b - confers specificity

Question 3

TSH inhibited by

Answer 3

SRIF
B agonists
Stress (glucocorticoids)

Question 4

TSH deficiency

Answer 4

rare - usually due to tertiary hypothyroidism

Question 5

Iodide uptake

Answer 5

“Iodide trapping”

-Active transport creates 20:1 iodide ratio

Question 6

TSH regulation of T3/4 production

Answer 6

++ Every fucking step

Question 7

Wolff-Chaikoff effect

Answer 7

Extreme iodide excess suppresses thyroid by inhibiting peroxide formation, decreases iodide trapping

Question 8

T3;4 t1/2

Answer 8

T3 - 1 day

T4 - 5-7 days

Question 9

T3 binding site

Answer 9

Nuclear hormone receptor

Question 10

Normal thyroid function

Answer 10

• Increase blood glucose
• Increase Na/K ATPase activity
• Increase heart rate and contractility

Question 11

-Levothyroxine-

Answer 11

Synthetic T4

• 1st line for routine replacement
• long half life

Question 12

-Liothyronine-

Answer 12

Synthetic T3

-Rapid, used for emergencies

Question 13

Different levothyroxine doses

Answer 13

• More for children and pregnant
• Loading dose for neonates
• Less for elderly and cardiac disease

Question 14

IV levothyroxine or liothyronine

Answer 14

Myxedema coma (hypothyroidism + illness)

Question 15

Drugs that induce CYP450 and increase T4 clearance

Answer 15

Phenytoin, Carbamazepine

Question 16

-Levothyroxine-

contraindications (4)

Answer 16

• Adrenal insufficiency (increases cortisol turnover)
• Diabetes (hyperglycemia)
• Cardiovascular disease
• Coumarin anticoagulants (increases clotting factor catabolism)

Question 17

Thionamides

Answer 17

Anti-thyroid agents (inhibit thyroid peroxidase)

• Methimazole (6 hour half life)
• Propylthiouracil (1.5 hour half life)

Question 18

Thionamide indications

Answer 18

• Graves
• Deplete T before surgery
• Deplete T before/after radioiodine Tx

Question 19

Thionamide AE

Answer 19

• Reversible agranulocytosis
• Hepatic abnormalities
  
  • necrosis (propylthiouracil)
  • cholestatic jaundice (methimazole)

Question 20

Radioactive Iodine (131)

Answer 20

• 8 day t1/2

- safe because of iodide trapping

Question 21

Thyrotoxic crisis Tx

Answer 21

• B or Ca blockers for symptoms
• Thionamide
• IV iodide (wolff-chaikoff effect)