Antithyroid drugs

Question 1

Once T3 and T4 are released from the thyroid gland they can bind with thyroxine binding globulin or be unbound in blood and be physiologically active. How do T3 and T4 enter their target tissues?

1 - diffuse into cells
2 - bind with ion channels causing intracellular cascade
3 - bind GPCR Gas and cause intracellular cascade
4 - bind tyrosine kinase receptors and cause intracellular cascade

Answer 1

1 - diffuse into cells

Question 2

What is the name given to patients with primary hyperthyroidism due to an autoimmune condition causing stimulation of the thyroid stimulating hormones?

1 - Addisons disease
2 - Graves disease
3 - Hashimoto’s disease
4 - Cushing’s Syndrome

Answer 2

2 - Graves disease

Question 3

Organise the following that occurs once T4 diffuses into target tissues:

1 - T3 binds with hormone receptor
2 - genes are up or down regulated
3 - T3-hormone receptor complex binds to DNA
4 - T4 converted to T3 by 5-deiodinase

Answer 3

4 - T4 converted to T3 by 5-deiodinase
1 - T3 binds with hormone receptor
3 - T3-hormone receptor complex binds to DNA
2 - genes are up or down regulated

Question 4

Thyroid hormones T3 and T4 are secreted from the thyroid. Primary hyperthyroidism is when the thyroid is not secreting sufficient thyroid hormones. Which 2 of the following are 1st line medications for treating hyperthyroidism?

1 - Levothyroxine
2 - Carbimazole
3 - Teriparatide
4 - Propylthiouracil

Answer 4

2 - Carbimazole
4 - Propylthiouracil

Question 5

Propylthiouracil and Carbimazole are an anti-thyroid medication that is classed as a thioamide and it used to treat hyperthyroidism. What is the mechanism of action of Propylthiouracil and Carbimazole?

1 - binds with receptors on cells so T4 cannot bind with cells
2 - absorbed by thyroid gland and inhibits thyroid peroxidase (TPO)
3 - inhibits Na+/iodine symptransporter

Answer 5

2 - absorbed by thyroid gland and inhibits thyroid peroxidase (TPO)

• TPO changes iodide into iodine so T3 and T4 can be made

Question 6

Propylthiouracil and Carbimazole is an anti-thyroid medication that is classed as a thioamide and it used to treat hyperthyroidism. Propylthiouracil and Carbimazole is able to inhibit thyroid peroxidase (TPO) which stops oxidation, iodination and coupling, essentially no T3 and T4 can be made? Is the therapeutic effect of Propylthiouracil and Carbimazole immediate?

Answer 6

• no
• iodine stores need to be gone
• so can take weeks before it is effective

Question 7

In addition to acting on the thyroid gland directly and inhibiting thyroid peroxidase (TPO), what else can Propylthiouracil and Carbimazole do in the peripheries?

1 - binds with receptors on cells so T4 cannot bind with cells
2 - inhibits thyroxine binding globulin
3 - inhibits 5-deionidase in tissues
4 - inhibits thyroid hormone receptor

Answer 7

3 - inhibits 5-deionidase in tissues
- T4 is not converted into T3

Question 8

Which if the following is NOT a adverse event of Propylthiouracil and Carbimazole?

1 - vasculitis
2 - hypothyroidism
3 - malignancy
4 - agranulocytosis
5 - cholestasis (bile stasis)
6 - hepatitis

Answer 8

5 - malignancy

• agranulocytosis is a rare but serious adverse event

Question 9

Is Propylthiouracil and Carbimazole used during pregnancy?

Answer 9

• yes
• BUT both at different time points
• BUT sholdnt really get pregnant until thyroid control is better

Question 10

In patients with hepatic and/or renal impairment, can they be prescribed Propylthiouracil and Carbimazole?

Answer 10

• yes
• BUT with caution, and a reduced dose
• MUST monitor for hepatotoxicity

Question 11

Do the blood results attached indicate hypo or hyperthyroidism?

Answer 11

• hyperthyroidism
• low TSH, BUT low T3 and T4
• indicates primary hyperthyroidism

Question 12

How are Propylthiouracil and Carbimazole typically administered?

1 - IV
2 - oral
3 - SB
4 - MI

Answer 12

2 - oral

• typically a course is 18-24 months

Question 13

Is Propylthiouracil or Carbimazole 1st line?

Answer 13

• Carbimazole
• use a titration - high to low as T3 and T4 begin to reduce