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Z YEAR 2 BRS ENDO > Thyroid Gland > Flashcards

Thyroid Gland Flashcards

1
Q

What is the control of thyroid activity?

A

Hypothalamus, pituitary and thymus

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2
Q

What type of disease is Grave’s?

A

Autoimmune

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3
Q

What does Grave’s cause?

A

Cause goitre (smooth) and hyperthyroidism

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4
Q

What do antibodies bind to and cause in Grave’s?

A
  1. bind to and stimulate the TSH receptor in the thyroid

2. bind to muscles behind the eye and cause exophthalmos

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5
Q

What else happens in Graves?

A
  1. Other antibodies cause pretibial myxoedema (hypertrophy)

2. The swelling (non-pitting) that occurs on the shins of patients with Graves’ disease: growth of soft tissue

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6
Q

What is Plummer’s disease?

A
  1. Toxic nodular goitre
  2. NOT autoimmune
  3. Benign adenoma that is overactive at making thyroxine
  4. High T4 and T3 but no TSH
  5. In iodine scale only tumour takes up iodine and not symmetrical and still bile to see some radiation in other areas unlike in Graves
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7
Q

What happens in Plummer’s?

A
  • NO pretibial myxoedema

* NO exophthalmos

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8
Q

What is the effect of thyroxine on the beta adrenoreceptors in sympathetic nervous system?

A
  1. Sensitises beta adrenoceptors to ambient levels of adrenaline and noradrenaline
  2. Sympathetic activation
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9
Q

What is are the symptoms of thyroxine’s effects on the sympathetic nervous system (hyperthyroidism)?

A
  1. Tachycardia
  2. Palpitations
  3. Tremor in hands
  4. Lid lag
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10
Q

What are the symptoms of hyperthyroidism?

A
  1. Weight loss despite increased appetite
  2. Breathlessness,
  3. Palpitations, tachycardia
  4. Sweating
  5. Heat intolerance
  6. Diarrhoea
  7. Lid lag and other sympathetic features
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11
Q

How dangerous are thyroid storms?

A

50% mortality untreated, sudden hyperthyroidism

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12
Q

What are symptoms of thyroid storm?

A
  1. Blood results confirm hyperthyroidism
  2. Hyperpyrexia > 41oC
  3. accelerated tachycardia / arrhythmia
  4. cardiac failure
  5. delirium / frank psychosis
  6. hepatocellular dysfunction; jaundice
    - Needs aggressive treatment
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13
Q

What are the treatment options for hypothyroidism?

A
  1. Surgery
  2. Radioiodine
  3. Drugs
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14
Q

What are the classes for drugs used to treat hyperthyroidism?

A
  1. The thionamides (thiourylenes;anti-thyroid drugs)
  2. Potassium Iodide
  3. Radioiodine
  4. β-blockers
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15
Q

What are examples of thionamides?

A
  • propylthiouracil (PTU)

- carbimazole (CBZ)

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16
Q

What do beta blockers do?

A

Help with symptoms only

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17
Q

What do thionamides, potassium iodide and radioiodine do?

A

reduce thyroid hormone synthesis

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18
Q

What is the clinical use of thionamides?

A
  1. Daily treatment of hyperthyroid conditions
  2. Graves’
  3. Toxic thyroid nodule/toxic multinodular goitre
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19
Q

What are the unwanted actions of thionamides?

A
  1. Agranulocytosis (usually reduction in neutrophils) - rare and reversible on withdrawal of drug - can become septic
  2. rashes (relatively common)
20
Q

What is the follow up after taking thionamides?

A
  1. Aim to stop anti-thyroid drug treatment after 18 months

2. Review patient periodically including thyroid function tests for remission/relapse

21
Q

What is the role of b blockers in thyrotoxicosis?

A
  1. Several weeks for ATDs to have clinical effects eg reduced tremor, slower heart rate, less anxiety
  2. NON-selective (ie b1 & b2) b blocker
    eg propranolol
    achieves these effects in the interim
22
Q

What does of iodide do you need and what form is it in?

A
  • KI

- At least 30 times. the average daily requirement (only works for 10 days)

23
Q

How does KI work?

A
  1. Inhibits iodination of thyrogobulin

2. Inhibits H2O2 generation + thyoperoxidase

24
Q

When do you give KI?

A
  1. preparation of hyperthyroid patients for surgery

2. severe thyrotoxic crisis (thyroid storm)

25
Q

What are the problems with surgeyr?

A
  1. Risk of voice change
  2. Risk of also losing parathyroid glands
  3. Scar
  4. Anaesthetic
26
Q

What does and isotope is radioiodine?

A
  1. Swallow a capsule about 370 MBq (10 mCi)

2. isotope I (131)

27
Q

When shoudl you not take radioiodine?

A
  • Pregnancy (can cross placenta?)

- Need to avoid children and pregnant mums for a few days

28
Q

What isotope can you use for scans not treatment?

A

99-Tc pertechnetate

29
Q

What drugs do you use to treat hyperthyroidism?

A

-Beta blockade e.g.
propranolol
-Anti thyroid: carbimazole, propylthiourcail

30
Q

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

A
  • Painful dysphagia
  • Hyperthyroidism
  • Pyrexia
  • Thyroid inflammation
31
Q

How does viral thyroiditis work?

A
  1. Virus attacks thyroid gland causing pain and tenderness
  2. Thyroid stops making thyroxine and makes viruses instead
  3. Thus no iodine uptake (ZERO) - no uptake in scan so no black!!!
32
Q

What is a result of the radioiodine uptake being zero?

A

-Stored thyroxine released

so toxic with zero uptake

33
Q

What happens four weeks into viral thyroiditis?

A
  1. Stored thyroxine exhausted so hypothyroid
  2. After another month resolution
  3. Then becomes euthyroid again
34
Q

When happens to TSH and T4 levels when the virus attacks the thyroid gland?

A
  1. All stored thyroxine released
  2. Free T4 levels rise
  3. TSH levels drop
  4. 1 month hyperthyroidism
  5. But NO new thyroxine is being synthesised
35
Q

How much thyroxine do you have in your thyroid gland?

A

Enough for a month

36
Q

What does TSH stimulate?

A
  1. Production of thyroxine

2. Activates proteolytic enzyme, makes whole and releases thyroxine into bloodstream

37
Q

What does T4 and T3. have Negative feedback on?

A

Suppress TRH (hypothalamus)and TSH (pituitary)

38
Q

How do you manage dose of thyroxine?

A

Increase dose until thyroxine falls to normal

39
Q

How do you measure graves?

A
  1. Iodine, goes into thyroid gland, uniform radioiodine uptake (in normal less black and intense)
  2. Diffuse and smooth goitre
40
Q

How do thionamides work?

A
  1. Inhibit thyroid peroxidase and hence T3/T4 synthesis and secretion
    - Reduces uptake if iodide active transport
    - Reduces iodination
    - Reduces coupling reaction; storage in. colloid
    - Less endocytosis and secretion
41
Q

How long does it take for thionamides to work?

A

biochemical, a few hours but clinically weeks (as still thyroxine that can come out)

42
Q

What would you give with thionamides?

A

Propranolol (beta blocker) as rapidly reduces tremor and tachycardia whilst waiting for drug to kick in

43
Q

What is inhibition of thyroid hormone synthesis and section with KI?

A
  • Wolff-chaikoff effect (presumed autoregulatory)
    1. Hyperthroid symptoms reduce in 1-2 days
    2. Vascularity and size of gland reduce. within 10-14 days
44
Q

What is postpartum thyroiditis?

A
  • Similar to viral thyroiditis but no pain and only occurs after pregnancy
  • Immune system is modulated during pregnancy
45
Q

What happens as FT4 slowly falls in viral thyroiditis?

A
  • Patient becomes hypothyroid – gland stops making thyroxine and just replicates virus
  • Hypothyroidism lasts a second month
  • After 3 months, there is slow recovery

Z YEAR 2 BRS ENDO (13 decks)

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