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Yr 2 LCRS - Endo > 5 - Hyperthyroidism > Flashcards

5 - Hyperthyroidism Flashcards

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1
Q

What are the 2 causes of Hyperthyroidism?

A

Grave’s Disease

Plummer’s Disease

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2
Q

What happens in Grave’s Disease to cause hyperthyroidism?

A
  • Autoimmune disease
  • Makes 3 types of antibodies

One of the antibodies stimulates the TSH receptors on the thyroid gland

  • causes gland to grow
  • causes smooth goitre

One of the antibodies stimulates receptors behind the eye
- exophthalmos

One of the antibodies bind to receptors in shins of patients

  • soft tissue growth
  • swelling (non-pitting)
  • pretibial myxoedema
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3
Q

What is a goitre?

A

A big thyroid gland

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4
Q

What are the signs and symptoms of hyperthyroidism?

A
  • lose weight
  • tachycardia (beta receptor-adrenaline)
  • tremor (beta receptors on skeletal muscle)
  • palpitations
  • can’t sleep
  • tired
  • overactive
  • emotional
  • breathlessness
  • sweating (hyperhidrosis)
  • heat intolerance
  • preoccupied/loss of focus
  • high appetite
  • increased bowel action (sometimes diarrhoea)
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5
Q

What are the specific symptoms that differentiate Grave’s Disease from Plummer’s disease?

A
  • Smooth Goitre
  • Whole thyroid grows
  • Exopthalmos
  • Pretibial Myxoedema (hypertrophy)
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6
Q

What are the specific symptoms that differentiate Plummer’s disease from Grave’s Disease?

A
  • Nodular Goitre
  • No eye and shin problems
  • Lump may only be on one side of gland
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7
Q

What happens in Plummer’s Disease to cause hyperthyroidism?

A
  • Toxic nodular goitre
  • Not autoimmune
  • Benign adenoma (may be 1-3+ tumours) that is overactive at making thyroxine
  • No pretibial myxoedema or exophthalmos
  • Normal part of gland shrinks
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8
Q

What is a Scintigraphy?

A

Scintigraphy (Gamma scan)vis a diagnostic test in nuclear medicine, where radioisotopes attached to drugs that travel to a specific organ or tissue (radiopharmaceuticals) are taken internally and the emitted gamma radiation is captured by external detectors (gamma cameras) to form 2D images.

  • give patient radioactive iodine/technetium
  • thyroid takes up iodine
  • can tell whether whole gland is overactive or just one cold nodule is underactive
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9
Q

How would you clinically differentiate between Grave’s and Plummer’s hyperthyroidism for a patient?

A

1) Examine
- check goitre, eyes, shins
2) Scan
- see if there is a single hot nodule e.g. in Plummer’s
3) Measure Antibodies

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10
Q

What is a cold nodule?

A

A cold nodule is a thyroid nodule that does not produce thyroid hormone.

A cancer from somewhere else that is growing in the thyroid.

Warm nodules would be normal thyroid tissue.

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11
Q

What does the normal part of the thyroid gland slowly atrophy in Plummer’s Disease?

A

Large tumour on one side of gland makes lots of extra thyroxine [hot nodule]

Suppresses pituitary TSH

The normal gland doesn’t need to produce much thyroxine as it’s getting less stimulation from the pituitary

Therefore, the normal part of the thyroid gland starts to shrink (atrophy)

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12
Q

What would you see on a scintigram of the thyroid of a patient with Plummer’s Disease?

A

A single hot nodule [the tumour]

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13
Q

What are the effects of thyroxine on the sympathetic nervous system?

A

Sensitises beta-adrenoreceptors to ambient levels of adrenaline and noradrenaline

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14
Q

Why does hyperthyroidism cause symptoms such as tachycardia and palpitations?

A

Thryoxine makes beta-adrenoreceptors more sensitive to ambient levels of adrenaline and noradrenaline

Therefore in hyperthyroidism, a small rise in adrenaline causes a large rise in heart rate

Thus there is apparent sympathetic activation

RESULTS IN:

  • tachycardia
  • palpitations
  • tremor in hands
  • lid lag
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15
Q

Why is lid lag a feature of hyperthyroidism?

A

Eyelids held open slightly by extra adrenaline (due to increased sensitivity of beta-adrenoreceptors as a result of lots of thyroxine) controlling the levator muscle in the eye

Sympathetic system is overactive

Eyelid held open by the adrenaline

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16
Q

What is the main difference between the development of Grave’s Disease compared to Plummer’s Disease in some people rather than others?

A

Grave’s Disease is heritable as autoimmune conditions are. Patients often have a family history of the hyperthyroidism

Plummer’s Disease is not heritable as tumours/lumps cannot be inherited.

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17
Q

What are the keys things you need to look for when attempting to uncover hyperthyroidism?

A

Weight loss despite increased appetite

Breathlessness

Palpitations, Tachycardia

Sweating

Heat intolerance

Diarrhoea

Lid lag and other sympathetic features

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18
Q

What is thyroid storm?

A

Occurs when patients with hyperthyroidism do not present early enough

Medical emergency

Hyperthyroidism with a few more clinical features

Blood results confirm hyperthyroidism

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19
Q

What is the mortality associated with untreated thyroid storm?

A

50% mortality

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20
Q

What are the clinical features of thyroid storm?

A

Hyperpyrexia >41 degrees

Accelerated tachycardia/arrythmia

Cardiac failure

Delirium/Frank Psychosis

Hepatocellular dysfunction; jaundice

= any 2 of these 5 things
= need aggressive treatment

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21
Q

What are the 3 overall categories of treatment options for hyperthyroidism?

A

Surgery (thyroidectomy)

Radioiodine

Drugs

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22
Q

What are the classes of drugs used to treat hyperthyroidism and what do they help to treat?

A

Thionamides (Thiourylenes/Anti-Thyroid Drugs)
- reduce thyroid hormone

Potassium Iodide
- reduce thyroid hormone

Radioiodine
- reduce thyroid hormone

Beta-Blockers
- help with symptoms

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23
Q

Which 2 particular thionamides are used to treat hyperthyroidism?

Study These Flashcards
A

Propylthiouracil

Carbimazole

24
Q

When are thionamides used to treat hyperthyroidism?

Study These Flashcards
A

The first drugs administered to a patient with hyperthyroidism (no matter the cause)

  • A short-term way to initially reduce thyroid hormone

Also used for:

  • A treatment prior to surgery so patient has normal thyroid function (so they’re not operated on whilst tachycardic etc)
  • Reduction of symptoms whilst waiting for radioactive iodine to act
25
What is the mechanism of action of thionamides?
MOA 1 Inhibit Thyroid Peroxidase enzyme - blocks 2 steps in thyroid hormone synthesis 1. Can't iodinate the thyroglobulin 2. Can't couple tyrosine residues into T3 and T4 MOA 2 May suppress antibody production in Graves' Disease MOA 3 Reduces conversion of T4 to T3 in peripheral tissues (Propylthiouracil not Carbimazole)
26
Why are beta-blockers used in the treatment of hyperthyroidism?
Beta-blockers help to reduce symptoms of hyperthyroidism before the clinical benefits of thionamide drugs begin to be seen by the patient.
27
Why are the clinical effects of thionamides not seen for 7-10 days following their administration to a patient with hyperthyroidism?
Thionamides act quickly on the thyroid gland, however the clinical benefits of their anti-thyroid effect aren't seen by the patient for some time. This is because their is a colloid store of thyroid hormone already made in the follicular cells of the thyroid gland. This must run out before the clinical effects of thionamides are seen.
28
Which form of beta-blockers are used for patients with hyperthyroidism?
Non-Cardio Selective Beta-Blockers e.g. propanolol Have beta-1 and beta-2 adrenergic effects - Have an effect on heart rate and palpitations - Also reduce peripheral symptoms such as hand tremor
29
What are some potential side effects of thionamides?
Agranulocytosis - usually reduction in neutrophils - rare and reversible on withdrawal of the drug - patients on these drugs must go for an urgent FBC if they get a sore throat/other signs of infection Rashes - relatively common
30
What are the pharmacokinetics of thionamides?
Orally active Carbimazole is a pro-drug - concerted first to methimazole Can cross placenta/Secreted in breastmilk - PTU < CBZ - young women are settled on lower doses before trying to get pregnant
31
What is the clinical follow-up for a patient on thionamides?
Usually aim to stop anti-thyroid drug treatment after 18 months Review patient periodically including thyroid function tests for remission/relapse
32
What is the chance of relapse following cessation of treatment with thionamides?
50/50 If thyroxine begins to rise again, the patient needs more definitive treatment
33
When is iodide used as treatment for hyperthyroidism?
- Preparation of hyperthyroid patients for surgery | - Severe thyrotoxic crisis (e.g. thyroid storm)
34
What form of iodide is typically used as treatment for hyperthyroidism?
Potassium Iodide (KI)
35
What is the treatment dose of iodide for patients with hyperthyroidism?
At least 30 times the daily average iodide requirement
36
What is thyrotoxicosis?
A medical condition caused by an excessive amount of thyroid hormones in the bloodstream. This is all the symptoms that result from severe hyperthyroidism.
37
What is the mechanism of action of KI for treatment of hyperthyroidism?
Dose of iodide given is much higher than normal daily requirement of iodine This stops the iodination of thyroglobulin in the synthesis of thyroxine Wolff-Chaikoff effect - mechanism poorly understood - presumed autoregulatory effect - potentially due to inhibition of thyroid peroxidase
38
How quickly does KI reduce symptoms of hyperthyroidism?
Within 1-2 days
39
What is the benefit of using KI to treat hyperthyroidism from a thyroid surgeon's perspective?
KI reduces the vascularity and size of the gland within 10-14 days
40
What is the main side effect of KI as a treatment?
Allergic reactions - rashes - fever - angio-oedema
41
What are the pharmacokinetics of KI as a hyperthyroidism treatment?
Given orally - Lugol's solution - aqueous iodine Maximum effects after 10 days of continuous administration It is a short-term treatment only
42
Why is KI only used as a short-term treatment for hyperthyroidism?
It works for a short time, but then thyroxine begins to rise very high
43
When is Radioiodine used as a treatment for hyperthyroidism?
As a definitive treatment for patients who have been on thionamides but either: - can't reduce the dose without raising thyroxine levels - stopped their course but their thyroxine has risen again
44
What is the mechanism of action of Radioiodine as a treatment for hyperthyroidism?
Taken up by iodine symporter on thyroid follicular cells Accumulates in colloid Emits beta particles because it's radiation The radiation destroys the gland by breaking down the follicular cells
45
What are the pharmacokinetics of Radioidoine as a treatment for hyperthyroidism?
Discontinue thionamides 7-10 days prior to radio iodine treatment Administer as a single oral dose - Graves' = 500 MBq - Thyroid cancer = 3000 MBq
46
What is the radioactivity of Radioiodine like?
Radioactive half-life = 8 days Radioactivity negabile = after 2 months
47
What is the advice given surrounding Radioiodine administration as a treatment for hyperthyroidism?
Discontinue thionamides 7-10 days prior to radio iodine treatment so that the gland is slightly overactive again before the treatment so that it takes up the radiation Avoid close contact with small children for several weeks after receiving radio iodine Conta-indicated in pregnancy and breast feeding Patient must wait several months before trying to get pregnant if this treatment is administered
48
Other than as treatment, what else is Radioiodine used for in endocrinology?
Radioiodine or Rechnetium 39 Pertechnetate Very low tracer doses Tests of thyroid gland pathology in scinitgraphy - toxic nodule - thyroiditis vs. Graves' etc. Administered I.V. Neglible cytotoxicity
49
What is Viral (de Quervain's) Thyroiditis?
Painful swelling of the thyroid gland thought to be triggered by a viral infection, such as mumps or the flu.
50
What are the symptoms of Viral (de Quervain's) Thyroiditis?
Painful dysphagia Hyperthyroidism (colloid leaks out) Pyrexia Raised ESR
51
What is Pyrexia?
Raised Body Temperature (Fever)
52
What is the mechanism behind Viral (de Quervain's) Thyroiditis?
Virus attacks thyroid gland causing pain and tenderness Thyroid stops making thyroxine Thyroid starts making viruses instead Thus iodine uptake is zero
53
Why are patients with Viral (de Quervain's) Thyroiditis thyrotoxic despite having an iodine uptake of zero?
Due to the thyroid gland being inflamed, colloid leaks out. This causes all stored thyroxine to all be released from the gland.
54
How would you know that a patient had a diagnosis of Viral (de Quervain's) Thyroiditis?
Radioiodine uptake is zero But all their stored thyroxine has been released = THYROTOXIC WITH ZERO IODINE UPTAKE
55
What happens to a patient approximately 4 weeks after their diagnosis with Viral (de Quervain's) Thyroiditis?
All their stored thyroxine has been exhausted They become hypothyroid (After a further month, resolution occurs as in all viral diseases. Patient becomes euthyroid again).
56
What does euthyroid mean?
Having a normally functioning thyroid gland.

Yr 2 LCRS - Endo (28 decks)

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