Thyroid Disorders

Question 1

Label the parts of the Thyroid

Answer 1

Question 2

What are the parathyroid glands?

Answer 2

Functionally unrelated - control calcium production

Located at the corners of the right and left lobes

Question 3

Which lobe is larger, and how much does the thyroid weigh?

Answer 3

Right lobe larger than left.

~20g in adults

Question 4

Where does the thyroid originate embryologically, and how does it develop?

Answer 4

Back of the tongue

Midline outpouching of floor of pharynx forms a thyroglossal duct which elongates downwards, allowing to migrate down the neck and divide into two loves; disappears to leave foramen caecum as thyroid gland develops in final position by week 7

Question 5

What is the Foramen Caecum?

Answer 5

A dimple at the back of the tongue originating from the disappearance of the thyroglossal duct

Question 6

What are the four possible problems with thyroid development?

Answer 6

1. Agenesis: never develops at all
2. Incomplete descent: does not descend fully from base of tongue to trachea
3. Thyroglossal cyst: segment of duct persist and presents as a lump years later
4. Lingual thyroid: no descent at all, remaining close to back of tongue and growing - need lifetime replacement of hormones if removed

Question 7

What is a cretin?

Answer 7

Baby without thyroid gland, as no thyroxine is produced resulting in lower IQ and stunted growth.

Question 8

How is cretinism detected?

Answer 8

Heel-prick test will show high TSH

Question 9

Why does cretinism occur in utero?

Answer 9

Mothers thyroxine crosses placenta

(also why thyroxine isn’t tested for in heel-prick test, as will still be present)

Question 10

What is Myxoedema?

Answer 10

Primary Hypothyroidism

Question 11

What causes myxoedema/primary hypothyroidism?

Answer 11

Autoimmune damage causes gland to fail

Thyroidectomy

Question 12

What can be detected in the blood during primary hypothyroidism?

Answer 12

Low thyroxine

High TSH - Until APG exhausted

(TRH also high, but cannot be detected in the blood)

Question 13

What are the symptoms of Myxoedema?

Answer 13

Sx:

• Deepening voice (cartilage vibrations slow down)
• Depression, tiredness, cold intolerance, constipation, bradycardia
• Eventual coma (BMR so low that become unconscious)
• Cardiomegaly

Question 14

What is the treatment for Myxoedema?

Answer 14

Tx:

• Thyroxine given daily
• Dose adjusted until TSH normal
• Needed otherwise death
  
  • ​Excess cholesterol increases risk of death from MIs and Strokes

Question 15

What is Thyrotoxicosis?

Answer 15

Hyperthyroidism

Question 16

What would be detected in the blood during thyrotoxicosis?

Answer 16

High Thyroxine

No TSH, as no need to stimulate production of thyroxine

Question 17

What are the symptoms of Thyrotoxicosis?

Answer 17

S_x:

• Myopathy
• Mood swings
• Diarrhoea
• Increased appetite
• Feeling hot
• Tremor
• Palpitations
• Sore eyes

Question 18

What is a cause of Hyperthyroidism?

Answer 18

Graves’ Disease

Question 19

What is Graves’ Disease?

Answer 19

Enlargement and overactivity of Thyroid gland

Question 20

What causes Graves’ Disease?

Answer 20

Immune system produces antibody similar to TSH.

Antibody binds to TSH receptor, stimulating gland which becomes overactive and enlarges (goitre)

Question 21

What are the other symptoms of Graves’ Disease?

Answer 21

• Goitre
• Pretibial Myxoedema (non-pitting swelling caused by growth of soft tissue on shins)
• Exophthalmos (proptosis) (pushing forewards of the eyes)