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BRS YR2 > Hyperthyroidism > Flashcards

Hyperthyroidism Flashcards

1
Q

What inhibits TRH and therefore TSH?

A

T4 and T3

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2
Q

What is Graves’ disease?

A
  • Autoimmune
  • TSH receptor antibodies (TRAb) bind and stimulate the TSH receptor in the thyroid
  • Causing a smooth goitre and hyperthyroidism
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3
Q

What are distinctive symptoms of Graves’ disease?

A
  • Exophthalmos
  • Pretibial myxoedema
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4
Q

What causes exophthalmos in people with Graves’ disease?

A

Antibodies binding to the muscles behind the eye

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5
Q

What is pretibial myxoedema?

A 
The swelling (non-pitting) that occurs on the shins of patients with Graves' disease (growth of soft tissue)
associated with hyperthyroidism NOT hypothyroidism
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6
Q

Describe the goitre caused by Graves’ disease.

A
  • Diffuse enlargement and engorgement of the thyroid gland
  • with uniform radioiodine uptake
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7
Q

What is the difference between toxic nodular thyroid disease and Graves’ disease?

A

Toxic nodular thyroid disease =

  • not autoimmune
  • no pretibial myxoedema
  • no exophthalmos
  • non-symmetrical and non-diffuse goitre
  • possible sore throat
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8
Q

What is toxic nodular thyroid disease?

A

Characterised by:

  • toxic nodular nodule or multinodular goitre
  • benign adenoma produces excess thyroxine
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9
Q

How does thyroxine impact the sympathetic nervous system?

A
  • sensitises beta adrenoreceptors to the ambient levels of adrenaline and noradrenaline
  • causes apparent sympathetic activation without adrenaline increasing
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10
Q

How does the impact of thyroxine on the sympathetic nervous system present?

A
  • tachycardia
  • palpitations
  • tremor in the hands
  • lid lag
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11
Q

What are the symptoms of hyperthyroidism?

A
  • weight loss (despite increased appetite)
  • breathlessness
  • palpitations
  • tachycardia
  • sweating
  • heat intolerance
  • diarrhoea
  • lid lag (+ other sympathetic features)
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12
Q

What is a thyroid storm?

A

A medical emergency resulting in a 50% mortality if untreated
(aggressive treatment is required)

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13
Q

What are the characteristics of a thyroid strom?

A
  • Hyperpyrexia (>41C)
  • accelerated tachycardia/arrhythmia
  • cardiac failure
  • delirium/frank psychosis
  • hepatocellular dysfunction; jaundice
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14
Q

What are the possible treatments for hyperthyroidism?

A
  • surgery (thyroidectomy)
  • radioiodine
  • drugs
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15
Q

What are the 4 classes of drugs involved in the treatment of hyperthyroidism?

A 
Thionamides (thiourylenes; anti-thyroid drugs)
- propylthiouracil (PTU)
- carbimazole (CBZ)
Potassium Iodide
Radioiodine
Beta-Blockers
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16
Q

What is the aim of thionamides, potassium iodide and radioiodine?

A

To reduce thyroid hormone synthesis

17
Q

What is the aim of Beta-blockers?

A

To help with the symptoms associated with hyperthyroidism

18
Q

What are the 2 main enzymes involves in thyroid hormone synthesis?

A
  • Thyroid peroxidase (TPO)
  • Peroxidase transaminase
19
Q

What is the mechanism of action of thionamides?

A

The inhibition of thyroid peroxidase and therefore T3/4 synthesis and secretion

20
Q

How long does it take for thionamides to come into effect?

A
  • biochemical effect: hours
  • clinical effect: weeks
21
Q

What drug often accompanies thionamides in a treatment plan?

A
  • Propanolol (beta-blocker)
  • rapidly reduces tremors and tachycardia
22
Q

Describe the synthesis of thyroid hormones

A
  • Uptake of iodide via active transport
  • Iodination of thyroglobulin (TG) into MIT and DIT
  • Coupling reaction of MIT and DIT into T3 and T4: storage in the colloid
  • Endocytosis and secretion
23
Q

What are the unwanted actions of thionamides?

A
  • rashes (common)
  • Agranulocytosis (normally a reduction in neutrophils) - rare, and reversible by stopping the drug
24
Q

How to follow up on the patient using drugs to treat hyperthyroidism?

A
  • aim to stop the anti-thyroid drug treatment after 18 months
  • review patient periodically, including thyroid function tests for remission/relapse.
25
Q

Why are beta-blockers like propanolol involved in treatment plans with anti-thyroid drugs?

A

Anti-thyroid drugs take several weeks to have clinical effects, therefore non-selective beta-blockers do so in the interim.

26
Q

When is potassium iodide used?

A
  • in preparation for surgery
  • during a thyroid storm (severe thyrotoxic crisis)
  • usually in doses >30x daily requirement
  • NOT used in patients opting for medical treatment of Graves’
27
Q

What is the mechanism of action of potassium iodide?

A
  • Actual mechanism is unknown
  • Inhibits the iodination of thyroglobulin
  • Inhibits hydrogen peroxide generation and thyroperoxidase
28
Q

What is the impact of potassium iodide in hyperthyroidism?

A
  • inhibition of thyroid hormone synthesis and secretion
  • Wolff-Chaikoff effect
  • hyperthyroid symptoms reduce in 1-2 days
  • vascularity and size of the gland reduce in 10-14 days
29
Q

What is the Wolff-Chaikoff effect?

A

presumed reduction in thyroid hormone levels caused by ingestion of a large amount of iodine

30
Q

What are the risks involved in surgery/thyroidectomy?

A
  • risk of voice change
  • risk of parathyroid gland loss
  • scarring
  • risk involved in anaesthesia
31
Q

What do people taking radioiodine need to do?

A

need to avoid children and pregnant women for a few days

32
Q

When is radioiodine contrindicated?

A

Pregnancy

33
Q

What are the symptoms of Viral (de Quervain’s) thyroiditis?

A
  • painful dysphagia
  • hyperthyroidism
  • pyrexia
  • thyroid inflammation
  • one-sided visible enlargement of the thyroid gland
34
Q

What causes Viral (de Quervain’s) thyroiditis?

A
  • virus attacks the thyroid gland causing pain and tenderness
  • thyroid stops making thyroxine and makes viruses instead
  • therefore no iodine uptake (ZERO)
  • stored thyroxine is released
  • thus, thyrotoxic with 0 reuptake
  • 4 weeks later, stores are exhausted > hypothyroidism
  • 8 weeks later, resolution occurs
  • patient becomes euthyroid
35
Q

How does Viral (de Quervain’s) thyroiditis present?

A
  • painful neck
  • all stored thyroxine is released
  • fT4 levels rise
  • TSH levels drop
  • 1 month of hyperthyroidism
  • no new thyroxine synthesis
  • fT4 slowly falls
  • patients becomes hypothyroid (thyroid just replicates the virus)
    lasts another month
  • after 3 months, slow recovery
36
Q

What is the difference between viral (de Quervain’s) thyroiditis and postpartum thyroiditis?

A

postpartum thyroiditis has no pain, and only occurs post pregnancy

37
Q

What are thionamides used to treat?

A
  • Grave’s disease
  • Toxic nodular thyroid disease

BRS YR2 (67 decks)

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