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Semester 2 - MEH > 22. Thyroid dysfunction > Flashcards

22. Thyroid dysfunction Flashcards

1
Q

Why does the thyroid move up on swallowing?

A

Because it is invested within the pre-trachial fascia

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2
Q

Which form of thyroid hormone has the lonest half-life?

A

T4

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3
Q

Thyroid hormone secreted from the thyroid gland is mostly in which form?

A

90% of the thyroid hormone secreted by the thyroid gland is in the form of T4. Most of this T4 is subsequently converted to T3 in the liver and Correct kidneys. The biological activity of T3 is approximately 4 times greater than that that of T4.

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4
Q

Clinically, how can you check if the lump in the neck is due to thyroid?

A

Lump will move up when swallowing if due to the thyroid

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5
Q

Which artery provides major blood supply to the thyroid gland?

A

Superior thyroid artery

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6
Q

How can you tell by someone’s body weight if they have hyp or hyper thyroidism?

A

Thyroid hormones control metabolic rate

hyper - skinny
hypo- fat
exaggerated

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7
Q

Which systems in the body are affected by thyroid hormones?

A

Thyroid hormones affect all systems in the body

  • Energy
  • Weight
  • Temperature
  • Heart rate
  • Nervous system
  • GI system
  • Muscu
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8
Q

What are the biochemical effects of primary hypothyroidism?

A

underactive thyroid:

fT4 low
TSH high (due to negative feedback)
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9
Q

What are the biochemical effects of primary hyperthyroidism?

A

overactive thyroid:
fT4 high
TSH low

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10
Q

What does a palpable thyroid gland indicate?

A

It is enlarged

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11
Q

What imaging techniques can be used to visualise the thyroid gland?

A
  • thyroid ultrasound
  • radioisotope scan
  • X rays
  • CT scan
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12
Q

Why might a lingual thyroid form?

A

Thyroid gland begins development at the base of the tongue

- embryological abnormalities during development may cause a mass of ectopic thyroid tissue

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13
Q

What imaging technique is best for finding ectopic thyroid tissue?

A

Radio isotope scan with Technetium-99m

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14
Q

What are the symptoms of hypothyroidism?

A
  • Tiredness
  • Weight gain
  • Cold intolerance
  • Change in appearance
  • Depression
  • Psychosis
  • Joint / muscle ache
  • Dry hair / skin
  • Constipation
  • Puffy eyes
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15
Q

What are the signs of hypothyroidism?

A
  • Peri-orbital oedema
  • ‘Peaches and cream’ skin colour
  • Loss of eyebrows
  • Dry, thin hair
  • Bradycardia
  • Slow-relaxing reflexes
  • Carpal tunnel syndrome
  • Cold peripheries
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16
Q

What are some causes of hypothyroidism?

A
  • Auto-immune atrophic (atrophic thyroditis)
  • Hashimoto’s thyroiditis
  • Post-partum thyroiditis
  • Congenital e.g. dyshormonogenesis
  • Medication
  • Iodine deficiency
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17
Q

What is dyshormonogenesis?

A

Rare condition due to genetic defects in the synthesis of thyroid hormones

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18
Q

What is the treatment for hypothyroidism?

A

Thyroxine replacement therapy

- Levothyroxine (T4) for life

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19
Q

What does dosage of thyroxine replacement depend on?

A

Starting dose depends on severity

100µg for young and fit person

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20
Q

In which patients should more caution be taken in thyroxine replacement?

A

More caution in elderly and heart disease

- avoid effects of hyperthyroidism (e.g. tachycardia)

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21
Q

How long would you expect normalisation of blood tests after thyroxine replacement?

A

Takes 6-8 weeks

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22
Q

how can you tell if thyroxine treatment is effective?

A

High TSH suggests under-replacement

Low TSH suggest over-replacement

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23
Q

What is myxoedema coma and who does it usually effect?

A

Severe hypothyroidism usually in the elderly

24
Q

What are the clinical presentations of myxoedema coma?

A

Hypothermia and fluid overload in heart pericardial effusion

25
Q

What is the mortality rate of myxoedema coma?

A

50% mortality so requires high dependency treatment

26
Q

What is borderline or sub-clinical hypothyroidism?

A

Low normal fT4 and high TSH
More common than severe
hypothyroidism
Can be monitored until symptoms warrant treatment

27
Q

What are the symptoms of hyperthyroidism?

A
  • Weight loss • Irritability
  • Restlessness • Insomnia • Malaise
  • Itching • Sweating • Palpitations
  • Tremor • Muscle ache • Diarrhoea
28
Q

What are the signs of hyperthyroidism?

A
  • Tremor • Hyperkinesis
  • Tachycardia • Atrial fibrillation
  • Warm peripheries • Hypertension • Proximal myopathy • Lid lag & retraction
29
Q

What causes lid lag and retraction in hyperthyroidism?

A

Sympathetic hyperactivity, which causes excess contraction of Müller muscle & levator palpebrae superioris??

30
Q

What are some causes of hyperthyroidism?

A
  • Graves disease (autoimmune)
  • Nodular thyroid disease
  • Thyroiditis (inflammation)
31
Q

What are 2 signs would be indicative of Graves’ disease over other types of hyperthyroidism?

A

Exophthalmos and Pre-tibial myxoedema

32
Q

What happens in Grave’s disease?

A

It is an autoimmune disease in which antibodies (Thyroid stimulating immunoglobulin (TSI)) arem produced that stimulate the TSH receptors on follicle cells resulting in increased production and release of T3 & T4. TSH levels fall due to the negative feedback exerted by T3 & T4 on the Anterior pituitary gland however this does not affect thyroid hormone secretion since the stimulus for thyroid hormone release is from TSI rather than TSH

33
Q

What is exophthalmos and what causes it in hyperthyroidism?

A

Bulging of the eye anteriorly out of the orbit.
Caused by an infiltration of the orbital connective tissue by lymphocytes and other immune cell types in response to TSI recognising antigens in orbital fat and connective tissue. The inflammation results in a deposition of collagen and glycosaminoglycans in the muscles leading to subsequent enlargement and fibrosis

34
Q

What is pre-tibial myxedema?

A

Infiltrative dermopathy that is as a rare complication in about 1-5% of patients suffering with Graves’ disease. Again pre-tibial myxoedema is a consequence of TSI rather than an increase in thyroid hormone

35
Q

What are the 2 types of nodular hyperthyroidism?

A
  • single toxic nodule

- toxic multinodular goitre

36
Q

What are 2 causes of thyroiditis which cause hyperthyroidism?

A 
Viral infection (de quervain's thyroiditis)
After childbirth (post-partum)
Medication
37
Q

What medication can cause hyperthyroidism thyroiditis?

A

Amiodarone

38
Q

What re the 3 types of treatment for hyperthyroidism?

A
  • medication
  • surgery
  • radioactive iodine
39
Q

What medication can be used to treat hyperthyroidism?

A

Carbimazole or Propylthiouracil (thionamides)

40
Q

What is a side effect carbimazole?

A

Agranulocytosis (neutropaenia)

  • risk of infections
  • stop the drug if infection develops
41
Q

What is given to patients on carbimazole?

A

Beta-blockers for symptoms control

42
Q

What risk does surgery for hyperthyroidism present?

A

Small risk of laryngeal nerve palsy and hypocalcaemia(damage to parathyroid gland)

43
Q

When should radioactive iodine not be used to treat hyperthyroidism?

A

Contra-indicated in pregnancy

44
Q

What is thyroid crisis/storm?

A

Life-threatening health condition that is associated with untreated or undertreated hyperthyroidism

45
Q

How does carbimazole work?

A

a drug that inhibits the incorporation of iodine into thyroglobulin. Carbimazole inhibits the enzyme thyroid peroxidase and therefore prevents coupling and iodination of tyrosine residues on thyroglobulin

46
Q

What are the clinical presentations in thyroid crisis?

A

Hyperpyrexia, tachycardia, cardiac failure, liver dysfunction

Needs urgent treatment on high dependency unit

47
Q

What is the risk of a person with Grave’es disease passing it on to baby when pregnant?

A

Antibodies can cross placenta

  • the baby can be born with hyperthyroidism
  • requires close monitoring in pregnancy
48
Q

What are the 4 types of goitre?

A
  • Diffuse goitre
  • Nodular goitre
  • Fibrotic goitre (Riedel’s thyroiditis)
  • Idoine deficiency
49
Q

What is diffuse goitre and when is it commonly seen?

A

Whole thyroid appearing to be enlarged due to hyperplasia

  • autoimmune thyroid diease
  • thyroiditis
50
Q

What is fibrotic goitre?

A

Replacement of the normal thyroid parenchyma by a dense fibrosis that invades adjacent structures of the neck and extends beyond the thyroid capsule. This makes the thyroid gland stone-hard (woody) and fixed to adjacent structures

51
Q

If there is a lump exactly in the midline and moves up when sticking tongue out, what could it be?

A

thyroglossal cyst

52
Q

What are the red flag symptoms of thyroid cancer?

A
  • Very young or old patient
  • Rapid enlargement of lump
  • Hoarse voice and dysphagia
  • Family history of thyroid cancer
  • Hard irregular thyroid mass
  • Fixed to surrounding structures
  • Cervical lymph nodes
53
Q

What investigations should be done in suspected thyroid cancer?

A

Thyroid ultra-sound
Fine needle aspiration
CT scan thorax and mediastinum

54
Q

Does Hashimotos and Graves mostly effect men or women?

A

Women

55
Q

Cause of Hashimoto’s

A

It is an autoimmune disease that results either in the destruction of the thyroid follicles or the production of an antibody that blocks the TSH receptor on follicle
cells preventing them from responding to TSH. Patients are generally treated with oral thyroxine

Semester 2 - MEH (23 decks)

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