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BRS - Year 2 > **_🧪Endocrinology🧪- Hyperthyroidism > Flashcards

**_🧪Endocrinology🧪- Hyperthyroidism Flashcards

1
Q

Outline the hypothalamic-pituitary thyroid axis

A
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2
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

High TSH

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3
Q

Outline Graves’ disease

A

Autoimmune
Antibodies bind to and stimulate TSH receptors in the thyroid
Causes (smooth) goitre and hyperthyroidism

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4
Q

What are the key features of Graves’?

A
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5
Q

What are the 2 most key features of Graves’, completely specific to Graves’?

A

Exophthalmos
Pretibial myxoedema

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6
Q

How do exophthalmos and pretibial myxoedema arise in hyperthyroidism?

A

Other antibodies bind to muscles behind the eye and cause exophthalmos
Other antibodies cause pretibial myxoedema (hypertrophy)

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7
Q

What is pretibial myxoedema?

A

The swelling (non-pitting) that occurs on the shins of patients with Graves’ disease: growth of soft tissue
Not to be confused with myxoedema=hypothyroidism

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8
Q

How can Graves’ be diagnosed?

A

TSH-receptor antibody (TRAb) (against the TSH receptor)
Measured in the bloodstream, positive in Graves’ disease
First-line investigation to confirm Graves’ disease

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9
Q

What would a radioiodine scan of a thyroid look like in Graves’

A
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10
Q

Outline toxic nodular thyroid disease

A

Single toxic nodule/multiple toxic nodules (multinodular goitre)
NOT autoimmune
Benign adenoma(s) overactive at making thyroxine.
NO pretibial myxoedema
NO exophthalmos

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11
Q

How would toxic nodular thyroid disease appear?

A
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12
Q

What effects does thyroxine have on the sympathetic nervous system>

A

Sensitises beta-adrenoceptors to ambient levels of adrenaline and noradrenaline
Therefore, there is apparent sympathetic activation
Leads to tachycardia, palpitations, tremor, lid lag

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13
Q

What are the features of hyperthyroidism?

A

Weight loss despite increased appetite
Breathlessness
Palpitations, tachycardia
Sweating
Heat intolerance
Diarrhoea
Lid lag and other sympathetic features

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14
Q

What is a thyroid storm?

A

Thyroid gland releases a large amount of thyroid hormone in a short amount of time

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15
Q

Why are thyroid storms so serious?

A

Medical emergency: untreated has 50% mortality

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16
Q

What would someone experiencing a thyroid storm present with?

A

Hyperpyrexia > 41oC
Accelerated tachycardia / arrhythmia
Cardiac failure
Delirium / frank psychosis
Hepatocellular dysfunction; jaundice
Needs aggressive treatment

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17
Q

What are the treatment options for hyperthyroidism?

A

Drugs
Surgery
Radioiodine

18
Q

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

A

Thionamides (anti-thyroid drugs, propylthiouracil, carbimazole)
Potassium Iodide
Radioiodine
beta-blockers

19
Q

How are beta-blockers different from other drugs used to treat hyperthyroidism?

A

Other drugs reduced thyroid hormone synthesis
Beta-blockers just manage symptoms

20
Q

How are thionamides used?

A

Daily treatment of hyperthyroid conditions

21
Q

What is the mechanism of action of thionamides?

A

Inhibits thyroid peroxidase, so stopping activation of iodide ions and so production of MIT/DIT and thus thyroid hormones

22
Q

How long does it take for thionamides to take effect?

A

Biochemical effect occurs within hours
Clinical effect takes weeks

23
Q

Why does it take weeks for thionamides to have a clinical effect?

A

It only stops synthesis of new thyroid hormones - existing stores remain
Only once existing stores are depleted will the clinical effects be seen

24
Q

What are the unwanted actions of thionamides?

A

Agranulocytosis (usually reduction in neutrophils) - rare and reversible upon withdrawal of drug
Rashes - relatively common

25
Q

What is the follow up for hyperthyroid treatment?

A

Usually aim to stop anti-thyroid drug treatment after 18 months
Review patient periodically including thyroid function tests for remission/relapse

26
Q

What is the role of beta-blockers in thyrotoxicosis?

A

Takes several weeks for ATDs to have clinical effects
Non selective bet blockers - propranolol
Achieves clinical effects in the interim

27
Q

What is iodide (usually KI) ‘s role in thyrotoxicosis management?

A

Preparation of hyperthyroid patients for surgery
Severe thyrotoxic crisis (thyroid storm)
Not used in patients opting for long-term medical treatment of Graves’

28
Q

What is the mechanism of action of KI?

A

Induces the Wolff-Chaikoff effect (excess iodide levels in thyroid inhibits thyroid hormone synthesis)
Hyperthyroid symptoms reduce within 1-2 days
Vascularity/size of gland reduces within 10-14 days

29
Q

Why does Thiouracil lead to thyroid swelling?

A

Inhibition of T3/T4 synthesis leads to increased TSH levels
TSH stimulates thyroid growth

30
Q

What are the risks associated with thyroid surgery?

A

Risk of voice change (recurrent laryngeal nerve)
Risk of also losing parathyroid glands
Scar
Anaesthetic

31
Q

How is radioiodine taken?

A

Swallow a capsule containing about 370 MBq (10 mCi) of the isotope I (131)
Contraindicated in pregnancy
Need to avoid children and pregnant mums for a few days

32
Q

Briefly outline the pharmacological treatment options for hyperthyroidism?

A

Beta-blockers:
-Beta blockade is VERY IMPORTANT
-propranolol
Anti thyroid drugs :
-Carbimazole
-Propylthiouracil
Radioiodine

33
Q

What are the signs//symptoms of viral thyroiditis?

A

Painful dysphagia
Hyperthyroidism
Pyrexia
Thyroid inflammation

34
Q

What is the mechanism of viral thyroiditis?

A

Virus attacks thyroid gland causing pain and tenderness
Thyroid stops making thyroxine and makes viruses instead
Thus no iodine uptake (ZERO)

35
Q

How would a thyroid scan of Graves’ compare to that of viral thyroiditis?

A
36
Q

What is the classic progression of viral thyroiditis?

A

Radioiodine uptake zero
Stored thyroxine released in large quantities - hyperthyroidism
Thus toxic with zero uptake
Four weeks later, stored thyroxine exhausted, so hypothyroid
After a further month, resolution occurs (like in all viral diseases).
Patient then becomes euthyroid again.

37
Q

Briefly summarise pattern of thyroid activity in someone with viral thyroiditis

A

Patient exhibits viral thyroditis symptoms, becomes hyperthyroid
4 weeks later, thyroid hormone exhausted, so becomes hypothyroid
After a further month, resolves (like in most viral diseases), patient becomes euthyroid

38
Q

What other condition mimics the pattern of hyper- then hypo- thyroidism exhibited by viral thyroiditis?

A

Postpartum thyroiditis

39
Q

Why does postpartum thyroiditis occur?

A

Immune system modulated during pregnancy
After birth, immune bounce back can lead to autoimmune attack on thyroid

40
Q

What is the main difference between postpartum thyroiditis and viral thyroiditis?

A

Postpartum thyroiditis similar but no pain and only occurs after pregnancy

BRS - Year 2 (29 decks)

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