Thyroid Disorders

Question 1

Drawing of thyroid

Slide 9, lecture 7

Answer 1

Pyramidal lobe only occasionally above isthmus

Question 2

Where is the foramen caecum?

Answer 2

Dimple at back of tongue caused by disappearing thyroglossal duct (duct between tongue and thyroid)

Question 3

Adult thyroid weight?

Answer 3

20g

Question 4

How many lobes?

Which lobe is largest?

Answer 4

2

Right

Question 5

How many lobes?
Average size?
Which lobe is largest?

Answer 5

2
4cm x 2.5cm x 2.5cm
Right

Question 6

Embryology of thyroid
Origin?
Where do parathyroid glands come from
Final position by when?
What happens to duct?

Answer 6

Origins at midline outpouching of floor of pharynx (base of tongue)
Thyroglossal duct= outpouching forms a duct which elongates down during foetal growth
Migrates down neck, divides into two lobes
Bottom two parathyroid glands come from 3rd pharyngeal pounch, top two from 4th pharyngeal
7th week of foetal development, thyroid then develops
Duct disappears, leaves foramen caecum (dimple)

Question 7

What runs close to thyroid?

Damage?

Answer 7

Left recurrent laryngeal nerve (vocal cord supply)

Damage= changes in quality of voice/ difficulty talking

Question 8

Possible problems with thyroid development

Answer 8

Absence of it (agenesis)
Incomplete descent= lump in neck/ lingual thyroid (remove so swallowing= better, but lifetime supply of hormones required)
Thyroglossal cyst (segment of duct persists+ presents as a lump years later)

Question 9

Importance of thyroxine
Deficiency?
Prevention?

Answer 9

Normal brain development- thyroxine deficiency in uter irreversible brain damage
Cretin= no thyroid gland, irreversible brain damage, lack of growth, lower basal metabolic rate
Heel prick test measuring TSH, if it’s high, thyroxine given

Question 10

Draw a diagram of the action of a thyroid follicle

Slide 29, lecture 7

Answer 10

-

Question 11

How can you see the release of thyroxine?

Answer 11

white spots around follicles

Question 12

If there is thyroglobulin in the blood what does that mean?

Answer 12

Leak in thyroid

Not the same as thyroxine-binding globulin

Question 13

Thyroid disease affects?

More common in?

Answer 13

5% population
Females because immune system= more changeable because different antibodies= most thyroid diseases autoimmune so females more common

Question 14

Primary hypothyrodism (Myxoedema)
Caused by?
Leads to?
Clinical features?
Treatment?

Answer 14

Primary thyroid failure
Autoimmune damage to thyroid
Decrease T4/ thyroxine levels
Increase TSH levels (but that doesn’t help)

Deepening voice
Depression, tiredness
Cold intolerance
Weight gain, reduced appetite
Constipation
Bradycardia
Increased cholesterol (increased risk of death by heart attacks/ strokes)

Thyroxine replacement daily, monitor TSH, adjust dose until normal

Question 15

Diagram of hypothalamo-pituitary-thyroid axis

slide 39, lecture 7

Answer 15

-

Question 16

Different name of TSH

Answer 16

Thyrotropin

Question 17

Hyperthyroidism
Molecular cause?
Clinical signs?
Clinical symptoms?
Causes?

(Don’t need to know treatment)

Answer 17

Too much thyroxine
TSH levels=0
Cause= Antibodies that stimulate TSH receptor= increase thyroxine

Raised basal metabolic rate
Raised temperature
Burn up calories+ lose weight
Increased heart rate

Mood swings
Hot in all weather
Diarrhoea
Increased appetite but weight loss
Hand tremor
Palpitations
Sore eyes
Goitre (gland grows)

Grave’s disease- whole gland enlarged+ overactive, autoimmune, antibodies do several things:

1. Bind to and stimulate TSH receptor in thyroid= goitre+ hyperthyroidism.
2. Bind to muscles behind eye= exophthalmos (eye bulging anteriorly)
3. Stimulate growth of shins= pretibial myxoedema (swelling on shins) (not the same as myxoedema= hypothyroidism)