7 - General Thyroid Disorders

Question 1

Which nerves go behind the thyroid?

Answer 1

Left recurrent laryngeal nerves.

If damaged their voice might change/ have difficulty speaking.

Question 2

How much does the adult thyroid weigh?

Answer 2

20g.

Each lobe = 4 x 2.5 x 2.5 cm

Question 3

How many lobes are there?

Which is the largest?

Answer 3

4 lobes.

Right is the largest.

Question 4

What glands are found embedded in the thyroid?

Answer 4

Parathyroid glands.

Question 5

Draw the thyroid gland.

Answer 5

Drawing

Question 6

What is the origin of the thyroid gland?

Answer 6

Back of tongue

Question 7

What is the foramen caecum?

Answer 7

Dimple at the back of the tongue (disappearing thyroglossal duct)

Question 8

What is agenesis?

Answer 8

Agenesis - the failure of an organ to develop during embryonic growth.
= Complete absence of the thyroid gland.

Question 9

What other problems with development of the thyroid could occur?

Answer 9

• Incomplete descent (tongue to trachea)
• Thyroglossal cyst (segment of duct presents as a lump)
• Lingual thyroid (mass of thyroid at are of tongue)

Question 10

What is a cretin?

Answer 10

An individual with irreversible brain damage caused by lack of thyroxine.

Question 11

How is cretinism prevented?

Answer 11

Baby heel prick - blood test to measure TSH.

If TSH is high = thyroxine given.

Question 12

Where is thyroxin synthesised?

Answer 12

Thyroid folicular cells

Question 13

Draw a thyroid follicle cell.

Answer 13

Drawing

Question 14

Where is thyroglobulin found?

Answer 14

Inside the thyroid gland ONLY.

Question 15

What does thyroxine bind to in the circulation?

Answer 15

Thyroxine binding globulin. (75% of thyroxine is bound this way)

Question 16

What do thyroid hormones regulate?

Answer 16

Growth, development and metabolic rate.

Question 17

What is the female:male ratio of thyroid disease?

Answer 17

4:1 - much more common in females.

Question 18

What is another name for primary hypothyroidism?

Answer 18

Myxoedema

Question 19

What is primary hypothyroidism?

Answer 19

Primary thyroid failure

• Thyroxine levels fall
• TSH levels rise (negative feedback)

Question 20

What can cause primary hypothyroidism?

Answer 20

Autoimmune damage

Operation

Question 21

Draw the HPT (hypothalamic-pituitary-thyroid axis)

Answer 21

Drawing.
Hypothalamus - TRH
Pituitary - TSH released
Thyroid - T3 and T4 (thyroxine) released.
Negative feedback arrows.

Question 22

What does TRH stand for?

Answer 22

Thyrotropin releasing hormone.

Question 23

What does TSH stand for?

Answer 23

Thyroid stimulating hormone (thyrotropin)

Question 24

What are the features of primary hypothyroidism?

Answer 24

• Deeper voice
• Depression
• Tiredness
• Cold intolerance
• Weight gain BUT reduced appetite
• Constipation
• Bradycardia (slow HR)
• Eventual myxoedema coma.

Question 25

Why is treatment of hypothyroidism essential?

Answer 25

Patient will die | Cholesterol will rise - heart attack and stroke.

Question 26

How is hypothyroidism treated?

Answer 26

Replace thyroxine. 1 tablet daily. | Monitor TSH, adjust done until it is normal.

Question 27

What does an overactive thyroid gland do?

Answer 27

Make too much thyroxine.

Question 28

What is the name for an overactive thyroid gland?

Answer 28

Thyrotoxicosis/ Hyperthyroidism.

Question 29

What happens to TSH levels with hyperthyroidism?

Answer 29

They fall as the pituitary senses you have enough thyroxine.

Question 30

What happens to the metabolic rate with hyperthyroidism? What does this cause?

Answer 30

Raised metabolic rate. - Raised temperature - Burn calories quick & lose weight - Increased HR

Question 31

Symptoms of hyperthyroidism?

Answer 31

- Myopathy (weak muscles) - Mood swings - Feeling hot - Diarrhoea - Increased appetite BUT weight loss - Hand tremor - Palpitations - Sore eyes - Goitre (lump in front of neck)

Question 32

What causes hyperthyroidism?

Answer 32

Graves' disease - whole thyroid gland is smoothly enlarged & overactive.

Question 33

What causes Graves' disease?

Answer 33

Autoimmune - antibodies bind to TSH receptor in thyroid. | Causes goitre and hyperthyroidism.

Question 34

What is exophthalmos and why is it caused by Graves' disease?

Answer 34

Bulging of the eye out of its socket. | Cause - antibodies bind to muscles behind the eye.

Question 35

What is pretibial myxoedema and why is it caused by Graves' disease?

Answer 35

The swelling of shins - growth of soft tissue. | Caused by antibodies.

Question 36

What is the difference between myxoedema coma and pretibial myxoedema?

Answer 36

Myxoedema coma - hypothyroidism (loss of brain function as a result of severe low level of thyroxine in the blood) Pretibial myxoedema - hyperthyroidism (swelling of shins in Graves' disease)