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BRS 1b > Hyperthyroidism > Flashcards

Hyperthyroidism Flashcards

1
Q

Which cells respond to TSH?

A

Follicular cells of the thyroid gland

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2
Q

Which endocrine cells release TSH?

A

Thyrotrophs within the anterior pituitary gland

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3
Q

How is iodine pumped into follicular cell of the thyroid gland?

A

Sodium-iodine symporter, using secondary active transport.

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4
Q

How is iodide pumped from the follicle into the colloid?

A

Pendrin pumps within the apical membrane

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5
Q

Which thyroglobulin residues are iodinated?

A

Tyrosine residues

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6
Q

Which thyroid pro-hormone is iodinated?

A

Thyroglobulin

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7
Q

How is iodine activated into iodide?

A

Under the action of thyroid peroxidase in the presence of hydrogen peroxide.

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8
Q

Where does iodination occur within the thyroid gland?

A

Within the colloid

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9
Q

What are the two direct products of iodination of thyroglobulin within the colloid?

A

MIT and DIT

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10
Q

How is triiodothyronine formed?

A

Coupling of MIT and DIT

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11
Q

How is tetraiodothyronine formed?

A

Coupling of DIT molecules

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12
Q

Which thyroid hormone is active?

A

T3

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13
Q

Which structures are directly inhibited by thyroxine via negative feedback mechanisms?

A 
Anterior pituitary gland (thyrotrophs)
Hypothalamic neurones (secreting TRH)
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14
Q

What level of TSH will you find in a patient with primary hypothyroidism where the thyroid gland has been destroyed by the immune system?

A

There is an elevated TSH, considering thyroxine secretion from the thyroid gland is reduced. Thus through negative feedback mechanisms, TSH is elevated as a compromise.

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15
Q

Which drug is prescribed in patients with hypothyroidism?

A

Levothyroxine

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16
Q

How should levothyroxine be administered?

A

Levothyroxine is administered as oral preparations to patients, the dose is increases until the TSH levels are normal.

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17
Q

Which effect demonstrates the auto-regulatory function of iodine control?

A

Wolff-Chaikoff effect

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18
Q

What is the Wolff-Chaikoff effect?

A

The Wolff-Chaikoff effect demonstrates an autoregulatory function, whereby an excess ingestion of iodine inhibits thyroid peroxidase activity and thus reducing iodothyronine production within thyroid follicular cells, independent from the serum-level of thyroid-stimulating hormone (TSH).

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19
Q

What is the pathophysiology of Grave’s disease?

A

TSH Immunoglobulins binds to TSH receptors in the thyroid gland.
-Stimulation of TSH receptors subsequently result in smooth goitre formation and hyperthyroidism.

20
Q

What are the clinical features of Grave’s disease?

A 
Respiration, facial flushing
Muscle wasting
Shortness of breath
Heat intolerance 
Weight loss - despite increased appetite
Localised myxoedema 
Tremor
Sweating
Palpitations
Exophthalmos (proptosis)
21
Q

What is pretibial myxoedema?

A

The swelling that occurs on the shins of patients with Grave’s disease: growth of soft tissue

22
Q

What type of goitre is shown in a patient with Plummer’s disease?

A

Toxic nodular goitre

Benign nodules of the thyroid gland (not autoimmune associated)

23
Q

What type thyroid scan is conducted to identify the type of goitre?

A

Iodine-123 scan

24
Q

Which part of the thyroid gland uptakes iodine-123 in Plummer’s disease?

A

The toxic nodular goitre. The inactive thyroid gland is suppressed due to the adenoma.

25
Q

What is the effect of thyroxine on the heart rate?

A

Sensitives beta adrenoreceptors to ambient levels of adrenaline and noradrenaline.
This increases the heart rate ( tachycardia and tremor in hands)
-lid lag

26
Q

What are the main clinical features of a thyroid storm?

A 
Hyperpyrexia > 41
Accelerated tachycardia/arrhythmia
Cardiac failure
delirium/frank psychosis
Hepatocellular dysfunction; jaundice
27
Q

What are the main treatment options for a thyroid storm?

A

Thyroidectomy
Radioiodine
Drugs

28
Q

What class of drug is the main anti-thyroid?

A

Thionamides

  • Propylthiouracil (PTU)
  • Carbimazole (CBZ)
29
Q

What are the four main classes of drugs used in the treatment of hyperthyroidism?

A

1) Thionamides
2) Potassium Iodide
3) Radioiodine
4) Beta-blockers

30
Q

What purpose do beta-blockers have in terms of hyperthyroidism treatment?

A

Alleviate the symptoms concerned with arrhythmia.

31
Q

Which enzyme is inhibited by thionamides?

A

Thyroid peroxidase

32
Q

What is the mechanism of action of thionamides?

A

Inhibition of thyroid peroxidase and peroxidase transaminase, therefore reduce iodine activation and iodination of thyroglobulin into MIT & DIT.

33
Q

Why does it take 3-4 weeks for the clinical effects of anti-thyroid hormones to become apparrent?

A

There is a months store of thyroxine

34
Q

Which co-drug is prescribed alongside thionamides?

A

Propanolol rapidly reduces tremors and tachycardia.

35
Q

What are the unwanted actions of thinamides?

A

Agranulocytosis (reduction in neutrophils) - neutropenia increases risk of sepsis.
-Rashes (common)

36
Q

How long should anti-thyroid drugs typically be prescribed for?

A

18 months

37
Q

What is the role performed by beta blockers in thyrotoxicosis?

A

Reduces heart rate and beta adrenoreceptor sensitivity

38
Q

Which drug should be pre-operatively administered in hyperthyroid patients?

A

Potassium Iodide - induces Wolff-Chaikoff effect (10 days)

39
Q

What effect does KI have in hyperthyroid patients?

A

Inhibits hydrogen peroxide generation and thyroid peroxidase.

Reduces vascularity and size of gland (atrophy of thyroid gland)

Inhibits the iodination of thyroglobulin by inducing the Wolff-Chaikoff effect

40
Q

Which nerve is at risk of damage during a thyroidectomy?

A

The recurrent laryngeal nerve

41
Q

What are the associated risks with a thyroidectomy?

A

1) Risk of voice change
2) Risk of also losing parathyroid glands
3) Scar
4) Anaesthetic

42
Q

Which isotope is used in radioiodine?

A

Iodine 131

Emits radiation for 10 days therefore avoid pregnant individuals

43
Q

Which radioisotope is administered for a thyroid scan?

A

Tc-99

44
Q

What are the four main features of viral thyroiditis?

A

Painful dysphagia
Hyperthyroidism (The thyroid gland is tender and palpable)
Pyrexia (fever)
Thyroid inflammation

45
Q

Describe the pattern of iodine uptake in an individual with viral thyroiditis?

A

There is no iodine uptake as the thyroid gland stops making thyroxine.

46
Q

How is hyperthyroidism induced in individuals with viral thyroiditis?

A

Round follicle is damaged, subsequently causing stored thyroxine within the colloid to be released

47
Q

How is hypothyroid caused in individuals with viral thyroiditis?

A

Four weeks upon the onset of viral thyroiditis, stored thyroxine is depleted.

BRS 1b (62 decks)

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