Thyroid disease - booklet

Question 1

Thyroid gland embrylogical origin

Answer 1

Back of tongue
Migrates down to midline and sits anterior to trachea in neck
Can lead to remenent tissue such as lingual thyroid or thyroglossal duct cyst

Question 2

Anatomy thyroid gland

Answer 2

Left and right lobe connected by isthmus

Question 3

How can thyroid lump be distinguished?

Answer 3

By swallowing

Question 4

Nerve in close proximity to thyroid

Answer 4

RLN - laterally on each side
parathyroid posteriorly and can be damaged during surgery

Question 5

Supply to thyroid gland

Answer 5

• Inferior and superior thyroid arteries

Question 6

What is thyroid tissue made of?

Answer 6

Colloid - contains iodinated thyroglobulin
Neuroendocrine cells (C cells) - secrete calcitonin

Question 7

How is thyroglobulin synthesised?

Answer 7

By follicular cells surrounding it

Question 8

What makes thyroxine?

Answer 8

Comes from thyroglobulin

Question 9

When are calcitonin levels elevated?

Answer 9

In medullary thyroid cancer - rare and has genetic basis

Question 10

What are thyroid hormones made up of?

Answer 10

Iodinated tyrosine molecules
Form thyroxine (T4) and triiodothyronine (T3)

Question 11

Main thyroid hormone

Answer 11

T4
Converted peripherally to more potent and shorter acting T3

Question 12

T3 vs T4

Answer 12

Number indicates now many iodine atoms are in molecule

Question 13

How are thyroid hormones bound?

Answer 13

Thryoxine binding globulin (TBG)
Transthyretin
Albumin

Question 14

What is active thyroid hormone

Answer 14

The free hormone can act on thyroid receptors

Question 15

Main thyroid receptors

Answer 15

TRalpha TR beta

Question 16

Actions of thyroid hormones

Answer 16

• Increase BMR
• Affect growth in children
• CVS - increase HR
  Also effect CNS and repro

Question 17

Primary hypothyroidism

Answer 17

• Due to problem with thyroid gland itself
• Low T4 and high TSH

Question 18

Secondary hypothyroidism

Answer 18

Problem with pituitary
Low T4 and non-elevated TSH

Question 19

Hyperthyroidism results

Answer 19

High T3/T4
Supressed TSH

Question 20

Hyperthyroidism with non supressed TSH

Answer 20

• Unusual
• TSHoma
• Thyroid hormone resistance
• Assay interference

Question 21

What can affect TFTs?

Answer 21

• Can be affected by non thyroidal illness
• Need to be realtively well pt rather than acute illness
• Medication eg lithium and amiodarone
• Pregnancy

Question 22

Causes of hyperthyroidism

Answer 22

• Graves disease - most common
• Nodular - autonomous secretion from solitary toxic nodule, numerous nodules within toxic multinodular goitre
• Thyroiditis - viral infection, medication (amiodarone), after childbirth

Question 23

Cause Graves disease

Answer 23

• TSH receptor stimulating antibodies
• Typically affects young women
• Relapsing and remitting

Question 24

Classical features hyperthyroidism

Answer 24

• Weight loss
• Increased appetite
• Insomnia
• Irritability
• Anxiety
• Heat intolerance
• Palpitations
• Tremor

Question 25

Hyperthyroidism in children symptoms

Answer 25

• Accelerated growth
• Behavioural disturbance

Question 26

Signs hyperthyroidism

Answer 26

• Resting tachycardia (sinus of Afib)
• Warm peripheries
• Resting tremor
• Hyper-reflexia
• Lid lag

Question 27

Lid lag vs lid retraction

Answer 27

• Lid lag seen in any cause of hyperthyroidism - due to increased sympathetic tone in upper eyelid
• Lid retraction only seen in Graves

Question 28

Graves disease signs

Answer 28

• Thyroid eye disease
• Skin changes (dermopathy)
• Pre-tibial myxoedema
• Nail changes - similar to clubbing (thyroid acropachy)

Due to cross reactivity of TSH receptors in back of orbit and skin

Question 29

Investigation hyperthyroidism

Answer 29

Elevated free T4 and T3
Undetectable TSH

Question 30

If T3 elevated alone…

Answer 30

T3 - toxicosis

Question 31

If normal T3/T4 but supressed TSH?

Answer 31

Subclinical hyperthyroidism - suggests autonomous thyroid activity

Question 32

Elevated T3 and T4 with non-supressed TSH

Answer 32

• Unusual
• Needs more investigation

Question 33

Autoimmune disease markers for hyperthyroidism

Answer 33

• TPO - thyroid peroxidase antibodies
• TSHrAb - TSH receptor stimulating antibodies - more specific

Question 34

Investigations for thyroid disease

Answer 34

• TFTs
• Thyroid USS - nodular disease
• Nuclear imaging - technetium or iodine uptae isotope scan

Question 35

Iodine uptake isotope scan thyroid disease

Answer 35

• Graves uniform increase uptake
• Nodular - increased uptake in only autonomous nodule
• Thyroiditis - absent uptake

Question 36

Management of hyperthyroidism - medication

Answer 36

• Thionamides - Carbimazole and propylthiouracil
• Takes 4-6 weeks for results to normalise
• Beta blockers may be used untlil thyroid function returns to normal

Question 37

Other options of management of hyperthyroidism

Answer 37

• Surgery
• Radioactive iodine

Question 38

Side effect of thionamides

Answer 38

• Boen marrow supression
• If unexplained fever and sore throat occurs - need FBC to excude pancytopenia
• Drug should stop of neutrophils are low
• Common side effect is rash which dissapears after cessation

Question 39

What is involved in radioactive iodine management?

Answer 39

• Single dose of 131 Iodine

Question 40

Disadvantages of radioactive iodine

Answer 40

• Contraindicated in pregnancy
• Flare up of eye disease with pre-existing opthalmopathy
• Hypothyroidism caused - lifelong replacement thyroxine
• Small amount of radiation emitted - avoid contact with young children and pregnant women for first few weeks

Question 41

When is thyroid surgery used?

Answer 41

When people struggle to comply with radioactive iodine precautions eg avoiding young children if have kids etc

Question 42

What is done before surgery if thyroid function is not optimum?

Answer 42

• Beta blockade used during anaesthetic induction to avoid A-fib

Question 43

Complications thyroidectomy

Answer 43

• Bleeding
• Infection
• Damage to RLN
• Temporary or permanent hypocalcaemia (hypoparathyroidism causes)