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GERR Pharmacology > Thyroid Pharmacology > Flashcards

Thyroid Pharmacology Flashcards

1
Q

How many iodines does T3 and T4 have

A
  • T3 : 3

- T4 : 4

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2
Q

Where are thyroid hormones stored

A
  • in the colloid
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3
Q

Why would the treatment of someone with hyperthyroidism not work for the first 3-4 weeks

A
  • the colloid storage units have a lot of thyroid hormones stored
  • if the synthesis of TH is cut of the colloid can still release the thyroid hormones they have stored for a couple weeks
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4
Q

When is hypothalamus stimulated to release TRH

A
  • when cold , stressed or due to trauma
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5
Q

MOA of Thyroid hormone (T3 & T4 )

A
  • lipid soluble so they pass through cell membrane and bind to Thyroid Nuclear Receptor TR
  • bind to hormone responsive elements in DNA
  • change activity of RNA polymerase , gene transcription and translation of mRNA
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6
Q

What is the effect of Thyroid Hormone

A
  • increase metabolic rate
  • increase heat
  • increase oxygen & caloric consumption
  • increase heart rate
  • effect GTH and CNS development
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7
Q

Signs of Hyperthyroidism (thyrotoxicosis )

A 
1- nervous / edgy 
2- shaky 
3- palpitations 
4- Heat intolerance 
5- increased appetite 
6- decreased weight 
7 - manic levels of energy 
8- tremor 
9- sweaty / warm 
10 - tachycardia 
11- hyper refelxia
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8
Q

List the types of treatment for Hyperthyroidism and the pharmacological options

A

1- Surgical treatment is there’s tracheal compression , pharmacological if not
2- Drugs options :
- Block TH formation
- block & replace with artificial TH
- radioactive iodine kills thyroid = permanent hypothyroid
3 - symptomatic control

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9
Q

Is goitre a sign indicating hyperthyroidism

A
  • no it does not indicate what type of thyroid problem there is
  • blood tests are needed to see thyroid hormone levels
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10
Q

Explain what are block drugs and give examples

A
  • prodrug that inhibits iodination of thyroxine residue in thyroglobulin
  • thioureylenes : carbimazole
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11
Q

How are Thioureylenes administered, and how long does it take to work

A
  • orally

- within 12 hours it inhibits 90% of iodination ( half life of 6-15 hours )

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12
Q

What is the block drug regimen for hyperthyroidism

A
  • Carbimazole initially for 4-8 weeks ( 15-40 mg )
  • gradually reduce Rx to maintenance level once TSH is normal
  • maintenance level is 18 to 24 months
  • after discontinue if TSH levels are normal
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13
Q

Adverse effects of Thioureylenes

A
  • usually well tolerated
  • common : rash, nausea and less energy
  • rare: agranulocytosis ( have to warn the patient to report any infection symptoms once started on Carbimazole)
  • lowest effect given to pregnant women as carbimazole can cross placenta
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14
Q

What drug is given during the first 4 weeks while patient on carbimazole due to stored thyroxine still being released and WHY

A

1- propranolol : non-selective beta blocker

  • rapidly reliefs thyrotoxic symptoms
  • inhibits T4 to T3 conversion
  • improves palpitations , tremors , arrhythmias
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15
Q

What’s the one disadvantage of symptomatic relief drug for hyperthyroidism

A
  • has to be taken orally 3 times a day
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16
Q

Why are block and replace regimens now being used more than block regimens

A
  • ## Block and replace shrinks goitre quicker : for patient visual satisfaction
17
Q

What is the Block and replace regimen for hyperthyroidism

A
  • Carbimazole ( 40 -60 mg ): completely blocks thyroid
  • AND levothyroxine : replacement for thyroid hormone
  • given fro 18 months
18
Q

How does radioactive iodine work to treat hyperthyroidism

A
  • rapidly and selectively taken up in thyroid

- release beta particles that damage thyroid follicle cells

19
Q

What do patients on radioactive iodine have to be warned of

A
  • can’t nurse babys since radiation could be emitted from around the neck neck
20
Q

What is the adverse effect of radioactive iodine

A
  • after 3 or 4 months most of the gland has died off
  • patient will have permanently hypothyroidism ( iatrogenic )
  • have to take thyroid hormone tablet for rest of life
21
Q

What are signs of hypothyroidism

A 
1- feeling cold 
2- tiredness 
3- gained weight 
4- slow comprehension 
5- delayed reflexes 
6- poor appetite 
7- dry thickened skin 
8- loss of hair
22
Q

What is the treatment of Hypothyroid ( regimen )

A
  • Levothyroxine : artificial thyroid hormone ( T4)
  • introduced slowly and increased every 4 weeks
  • between 50 - 150 microg is given
23
Q

List side effects of hypothyroid treatment

A
  • non unless levothyroxine is given in excess

- has to be titrated

24
Q

What is Lugol’s iodine

A
  • iodine concentrate solution
  • sometimes used for short term control of thyrotoxicosis
  • reduced vascularity and fragility of gland ( for surgery )
25
Q

What is Amiodarone

A
  • anti-arrhythmic drug but has iodine

- can cause hypo or hyper thyroidism or BOTH

26
Q

What drugs can affect thyroid hormone synthesis

A
  • Thioureylenes
  • Iodides
  • Lithium : decrease thyroid function

GERR Pharmacology (9 decks)

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