Thyroid

Question 1

Where is T4 stored?

Answer 1

Thyroid gland

Question 2

Where is T4 converted to T3?

Answer 2

Periphery

Question 3

To which hormone is T4 mostly bound to?

Answer 3

Thyroxine-binding globulin

Question 4

List 5 causes of primary hypothyroidism.

Answer 4

Hashimoto's thyroiditis = autoimmune
Atrophic thyroid
Post Graves' Disease (radioactive iodine, surgery)
Post-thyroiditis
Drugs (amiodarone, lithium)

Question 5

What antibodies suggest autoimmune hypothyroidism?

Answer 5

Thyroid peroxidase autoantibodies

Question 6

What can happen as a result of giving too much T4?

Answer 6

Osteopaenia

Atrial fibrillation

Question 7

Which cholesterol condition is associated with hypothyroidism?

Answer 7

Hypercholesterolaemia

Question 8

What happens to thyroid hormone levels during pregnancy?

Answer 8

hCG has similar structure to TSH - so it can stimulate the thyroid gland to produce more T4. Thus T4 rises slightly in the first trimester of pregnancy.

TBG levels increase dramatically in pregnancy because it is under the control of oestrogen.

Later in pregnancy hCG levels will drop, thus so will T4 and TSH will rise slightly.

Question 9

How is neonatal hypothyroidism diagnosed?

Answer 9

Guthrie test

NOTE: must not be measured too early because maternal TSH can give false negative

Question 10

What is sick euthyroid?

Answer 10

An alteration in the axis in any severe non-thyroidal illness. The patients will not be symptomatic and giving thyroxine will not help.

Question 11

What are the 3 main causes of hyperthyroidism?

Answer 11

Graves’ disease
Toxic multinodular goitre
Single toxic adenoma

Question 12

What will a technetium scan show in the 3 main conditions that cause hyperthyroidism?

Answer 12

Increased uptake

Question 13

What are 2 other less common causes of hyperthyroidism?

Answer 13

Subacute thyroiditis
Post-partum thyroiditis

These will have LOW uptake.

Question 14

How is hyperthyroidism managed?

Answer 14

Beta blocker if tachycardic
Manage other autoimmune conditions
ECG
Bone mineral density

Radioactive iodine:

• NOTE: can precipitate a thyroid storm
• Can make thyroid gland underactive

Question 15

What are the clinical features of Graves’?

Answer 15

All features of hyperthyroidism
Diffuse goitre
Thyroid-associated ophthalmopathy
Thyroid-associated dermopathy (pretibial myxoedema)
Thyroid acropatchy
Other autoimmune conditions

Question 16

What drugs can be used in treating Graces’ disease?

Answer 16

Thionamides

Examples: carbimazole, propylthiouracil

Question 17

How do thionamides work?

Answer 17

Prevent the conversion of iodide to iodine by thyroid peroxidase

Question 18

What is a rare side effect of thionamides?

Answer 18

Agranulocytosis

Question 19

What are the two most common types of thyroid cancer?

Answer 19

Papillary

Follicular

Question 20

What drug is given after thyroidectomy for thyroid cancer?

Answer 20

High dose thyroxine - lowers TSH levels so any remaining cancer cells are not stimulated

Question 21

What can be measured as a tumour marker after thyroidectomy for thyroid cancer?

Answer 21

Thyroglobulin

Question 22

What is the severe type of thyroid cancer

Answer 22

Medullary carcinoma
Very rare
Sporadic/familial/MEN2
Cancer of C cells - produce calcitonin