Lecture 7 - Thyroid Disorders

Question 1

Draw a diagram of the thyroid

Answer 1

2 major lobes, L and R (largest) 4 parathyroid glands Isthmus in centre Pyramidal lobe in triangle

Question 2

What is the origin of the thyroid?

Answer 2

Back of the tongue

Question 3

Where is the foramen caecum?

Answer 3

Dimple at back of tongue (disappearing thyroglossal duct)

Question 4

What is the adult thyroid weight?

Answer 4

20g

Question 5

How many lobes are there?

Answer 5

4 lobes

Question 6

Where can you find aberrant parathyroid glands?

Answer 6

Can be higher up on neck

Question 7

What is the foramen caecum?

Answer 7

The entry to the persistent thyroglossal duct

Question 8

How is the thyroid formed embryologically?

Answer 8

Midline outpouching of floor of pharynx This forms duct which elongates down (thyroglossal duct) Migrates down neck and divides into 2 lobes

Question 9

When does thymus move into final position?

Answer 9

By week 7

Question 10

What happens to the thyroglossal duct?

Answer 10

It disappears leaving the foramen caecum, where the thyroid gland then develops

Question 11

What are the dimensions of each lobe?

Answer 11

4*2.5*2.5cm

Question 12

Which nerve runs close to the thyroid?

Answer 12

Left recurrent laryngeal nerve

Question 13

Why is it difficult to operate on the thyroid?

Answer 13

Damage to the nerve can cause changes in quality of voice/difficulty talking

Question 14

What are the main problems with development?

Answer 14

Agenesis Incomplete descent Thyroglossal cyst

Question 15

What is agenesis?

Answer 15

Complete absence of gland Not very good prognosis as no thyroxine released

Question 16

What is a thyroglossal cyst?

Answer 16

Segment of thyroglossal duct persists and presents as lump years later

Question 17

What is the prognosis of a lingual thyroid?

Answer 17

Can be lethal if not treated with thyroxine

Question 18

What is a lingual thyroid?

Answer 18

An ectopic thyroid present at the top of the throat, which hasn’t descended at all - surgery as treatment option

Question 19

Why is thyroxine essential for brain development?

Answer 19

Neonates with T4 deficiency in utero have irreversible brain damage - CRETIN

Question 20

What is a cretin?

Answer 20

Individual with irreversible brain damage caused by lack of thyroxine Has thicker tissues Stunted growth

Question 21

How do you diagnose and treat cretinism?

Answer 21

Heel prick test at 5-10 days (mother’s T4 can falsify test) - measures TSH or Phenylketonuria (Guthrie test) Thyroxine given immediately after - if TSH too high

Question 22

Where is thyroxine synthesised?

Answer 22

Thyroid follicular cell

Question 23

What does the colloid contain?

Answer 23

Thyroglobulin and stored thyroxine

Question 24

What is the difference between thyroglobulin and thyroxine binding globulin?

Answer 24

TBG bonds 75% of T4 in circulation VS Thyroglobulin is inside thyroid gland only

Question 25

Thyroid diseases affect which sex more?

Answer 25

Females in a 4:1 ratio - women more susceptible to auto-immune diseases

Question 26

What are the thyroid's common functions?

Answer 26

Synthesis, storage and secretion of thyroid hormones -\> regulate growth, development and metabolic rate

Question 27

Thyroid disease affects how much of the population?

Answer 27

5% - 1:1 ratio of over and underactive thyroids

Question 28

What are the type of thyroidisms?

Answer 28

Primary hypOthyroidism (myxoedema) Overactive thyroid gland (hypothyroidism) Graves' Disease

Question 29

What is Myxoedema - symptom of primary hypothyroidism?

Answer 29

1ry thyroid failure Autoimmune/operation damage to thyroid Thyroxine levels DECREASE \> TSH levels INCREASE

Question 30

What are some features of primary hypothyroidism?

Answer 30

Deepening voice Depression and tiredness Cold intolerance Weight gain with reduced appetite Constipation Bradycardia Eventual myxoedema coma

Question 31

What are some methods of treatment of primary hypothyroidism?

Answer 31

Essential - death otherwise: Cholesterol ^ causing death from heart attacks/stroke Replace thyroxine - monitor levels, ensuring TSH returns to normal

Question 32

What is an overactive thyroid gland?

Answer 32

TOO MUCH thyroxine TSH levels FALL to ZERO a.k.a. HYPERTHYROIDISM/THYROTOXICOSIS

Question 33

What are the symptoms of an overactive thyroid gland?

Answer 33

^ basal metabolic rate ^ temperature - hot ^ appetite, lose weight Tachycardia Myopathy Mood swings Diarrhoea Tremor of hands Palpitations Sore eyes, goitre

Question 34

What are the causes of an overactive thyroid gland?

Answer 34

GRAVES' DISEASE Toxic multinodular goitre Thyroiditis

Question 35

What is Graves' disease?

Answer 35

Whole gland is smoothly enlarged and overactive Autoimmune disease - Ab bind and stimulate TSH receptor Causes Goitre and HERT

Question 36

What are the symptoms of Graves' disease?

Answer 36

Proptosis, Periorbital oedema, PRETIBIAL MYXOEDEMA, Exopthalmos, Clubbing, Amenorrhea, Tremor

Question 37

What is pretibial myxoedema?

Answer 37

Swelling occurring on shins of Graves' patients - growth of soft tissue

Question 38

What are the thyroid levels signs of OTG?

Answer 38

^ T3 and 4 LESS TSH

Question 39

What are the thyroid level signs of OTG?

Answer 39

LESS T3 and 4 ^ TSH