Thyroid Gland

Question 1

Describe the shape of the thyroid gland.

Answer 1

Right and left lobes connected by a narrow isthmus.

Question 2

What do c-cells secrete?

Answer 2

Calcitonin.

Question 3

Which hormone is released by the hypothalamus to stimulate the pituitary to release TSH?

Answer 3

Thyrotropin releasing hormone (TRH).

Question 4

What is the function of thyroid stimulating hormone (TSH)?

Answer 4

Stimulates the thyroid gland to produce T3 and T4.

Question 5

Which cells produce T3 and T4?

Answer 5

Follicular cells.

Question 6

What is the precursor to T3 and T4?

Answer 6

Thyroglobulin.

Question 7

What enzyme binds iodine to tyrosine in thyroglobulin molecules? What are the products?

Answer 7

Thyroperoxidase.

Iodotyrosyl residues (MIT and DIT)

Question 8

How do iodide ions enter the follicular cells?

Answer 8

Through the Na/I symporter (NIS).

Question 9

Where is thyroperoxidase found?

Answer 9

On the apical membrane of the follicular cells.

Question 10

Where are thyroid stimulating hormone receptors found?

Answer 10

On the basolateral membrane of the follicular cells.

Question 11

Which enzyme couples iodotyrosyl residues?

Answer 11

Thyroperoxidase.

Question 12

Where is mature thyroglobulin stored?

Answer 12

In the colloid.

Question 13

Which enzyme is responsible for the mono-deiodination of T4 to T3?

Answer 13

Deiodinase (D1, D2 and D3).

Question 14

Where is deiodinase found?

Answer 14

In most peripheral tissues.

Question 15

List 3 plasma proteins that T3 and T4 bind to in the blood.

Answer 15

1 - TBG.

2 - Transthyretin.

3 - Albumin.

Question 16

What are the 3 tests for thyroid function?

Answer 16

1 - Serum TSH.

2 - Serum free T4.

3 - Serum free T3.

Question 17

What is goitre?

Answer 17

Enlargement of the thyroid gland.

Question 18

List 6 possible causes of hyperthyroidism.

Answer 18

1 - Grave’s hyperthyroidism.

2 - Toxic nodular goitre.

3 - Thyroiditis (inflammation).

4 - Exogenous iodine.

5 - TSH secreting pituitary adenoma.

6 - Neonatal hyperthyroidism.

Question 19

What is hyperthyroidism characterised by? What about hypothyroidism?

Answer 19

• *Increased serum free T4.
• *Increased serum T3.
• Decreased serum TSH.
• Hypothyoridism is the opposite.

Question 20

List 4 cardiovascular symptoms of hyperthyroidism.

Answer 20

1 - Tachycardia.

2 - Atrial fibrillations.

3 - Shortness of breath.

4 - Ankle swelling.

Question 21

List 3 gastrointestinal symptoms of hyperthyroidism.

Answer 21

1 - Weight loss.

2 - Diarrhoea.

3 - Increased appetite.

Question 22

List 3 neurological symptoms of hyperthyroidism.

Answer 22

1 - Tremor.

2 - Myopathy.

3 - Anxiety.

Question 23

List 5 symptoms of hyperthyroidism relating to the eyes and skin.

Answer 23

1 - Sore, gritty eyes.

2 - Double vision.

3 - Staring eyes.

4 - Itching (pruritis).

5 - Conjunctival oedema.

Question 24

What is Grave’s disease?

Answer 24

• An autoimmune disorder characterised by pathogenetic TSH-R antibodies that stimulate TSH receptors on thyroid follicular cells.
• Accounts for 70% of cases of hyperthyroidism.

Question 25

List 5 environmental factors that can contribute to Grave's disease.

Answer 25

1 - Gender. 2 - Stress. 3 - Infection. 4 - Pregnancy. 5 - Drugs.

Question 26

What is proptosis?

Answer 26

Bulging of the eyes.

Question 27

What is opthalmoplegia?

Answer 27

Paralysis of the muscles surrounding the eyes.

Question 28

List 3 symptoms of thyroid eye disease.

Answer 28

1 - Lid retraction. 2 - Proptosis. 3 - Opthalmoplegia.

Question 29

How does neonatal hyperthyroidism develop?

Answer 29

TSH-R antibodies cross the placenta.

Question 30

Other than measuring TSH, T4 and T3, give an example of how hyperthyroidism can be diagnosed.

Answer 30

PET scan | - Uptake of radioactive iodine.

Question 31

List 3 treatment options of hyperthyroidism.

Answer 31

1 - Antithyroid drugs such as carbimazole or propylthioracil to block hormone synthesis. 2 - Surgical removal of thyroid. 3 - Radioiodine therapy.

Question 32

How does propylthiouracil block thyroid hormone synthesis?

Answer 32

By inhibiting thyroperoxidase.

Question 33

List 5 causes of hypothyroidism.

Answer 33

1 - Autoimmune - Hashimoto's thyroiditis (TPO and Tg antibodies). 2 - Treatment for hyperthyroidism (iatrogenic). 3 - Thyroiditis. 4 - Iodine deficiency. 5 - Congenital - enzyme defects or thyroid agenesis (does not develop as an embryo).

Question 34

What is cretinism?

Answer 34

Congenital hypothyroidism.

Question 35

List 3 cardiovascular symptoms of hypothyroidism.

Answer 35

1 - Bradycardia. 2 - Heart failure. 3 - Pericardial effusion.

Question 36

List 2 gastrointestinal symptoms of hypothyroidism.

Answer 36

1 - Weight gain. 2 - Constipation.

Question 37

List 3 symptoms of hypothyroidism that relate to the skin.

Answer 37

1 - Myxoedema (swelling of the skin). 2 - Erythema (redness of the skin). 3 - Vitiligo (loss of skin pigmentation).

Question 38

List 3 neurological symptoms of hypothyroidism.

Answer 38

1 - Depression. 2 - Psychosis. 3 - Carpal tunnel syndrome.

Question 39

How is hypothyroidism treated?

Answer 39

Hormone replacement therapy using levothyroxine.