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Year 2 - T2 Theme 1 > L8 - Thyroid disease > Flashcards

L8 - Thyroid disease Flashcards

1
Q

What is hypothyroidism

A
  • Underproduction of thyroid hormone
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2
Q

Primary vs secondary hypothyroidism

A
  • Primary = due to a thyroid problem

- Secondary = due to a hypothalamic/pituitary problem

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3
Q

What is hyperthyroidism

A
  • Hyperthyroidism = thyrotoxicosis = overproduction of thyroid hormone
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4
Q

What is euthyroid

A
  • Normal production of thyroid hormone
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5
Q

What is a goitre

A
  • Enlargement of thyroid gland
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6
Q

Examination of the thyroid

A
  • Low down in neck
  • Feel for thyroid cartilage (‘Adam’s apple’) then down & laterally
  • Moves on swallowing
  • Listen for a bruit
  • Retrosternal extension
    • Can you get below it?
    • Percuss over sternum
  • Check cervical LNS
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7
Q

What is a retrosternal goitre

A

Retrosternal goitre is defined as a goitre with a portion of its mass ≥ 50% located in the mediastinum.

Surgical removal is the treatment of choice and, in most cases, the goitre can be removed via a cervical approach

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8
Q

Where is TSH mainly produced

A
  • TRH is mainly secreted mainly from the paraventricular nucleus in the hypothalamus and reaches the eminence through axonal transport
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9
Q

Thyroid function tests

A

TSH: 0.3 -4.2 mu/l
FT4: 12-22 pmol/l
FT3: 3.1-6.8 pmol/l

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10
Q

Thyroid autoantibodies

A
  • Anti-TPO AB - thyroid peroxidase auto-antibody

- TRAB - TSH receptor autoantibody

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11
Q

What is the best ‘biomarker’ of thyroid status

A

TSH

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12
Q

Features of changes in TSH levels as a ‘biomarker’ of thyroid status

A

• Shape of curve
• ‘tail’ from 3 upwards
○ ­ Increase in frequency thyroid autoantibodies
• Slow to respond to change
• about 6 weeks
• Assumes normal pituitary function
• Remember the negative feedback regulation!

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13
Q

Features of thyroid autoantibodies

A

• Prevalence of autoAB > autoimmune disease
• Marker of risk, or causal?
• Many autoAg are sequestered / intracellular
‘Negative’ autoAB result does not exclude autoimmune disease; presence helps confirm diagnosis

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14
Q

Types of thyroid autoantibodies

A

‘destructive’ - target thyroid for autoimmune destruction

‘Stimulatory’ - Stimulate TSH receptor

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15
Q

Symptoms of hypothyroidism

A
  • May be none
  • Lethargy
  • Mild weight gain
  • Cold intolerance
  • Constipation
  • Facial puffiness
  • Dry skin
  • Hair loss
  • Hoarseness
  • Heavy menstrual periods
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16
Q

Signs of severe hypothyroidism

A
  • Change in appearance eg face puffy and pale
  • Periorbital oedema
  • Dry flaking skin
  • Diffuse hair loss
  • Bradycardia
  • Signs of median nerve compression (carpal tunnel)
  • Effusions, eg ascites, pericardial
  • Delayed relaxation of reflexes
  • Croaky voice
  • Goitre
  • Rarely stupor or coma
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17
Q

Causes of primary hypothyroidism

A 
• Autoimmune hypothyroidism
• Hypothyroidism after treatment
     for hyperthyroidism (iatrogenic)
• Thyroiditis
• Drugs (e.g. lithium, amiodarone)
• Congenital hypothyroidism
• Iodine deficiency (not UK)
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18
Q

TSH, T4 and T3 levels in primary hypothyroidism

A
  • Increase in TSH
  • Decrease in T4
  • Decrease in T3
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19
Q

Cause of secondary hypothyroidism (RARE)

A
  • Failure of the pituitary gland to secrete thyroid stimulating hormone (TSH). This is usually caused by a tumor in the region of the pituitary
  • Rarely the cause is an infiltration of the pituitary by inflammatory cells from the immune system or foreign substances (such as iron in hemochromotosis).
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20
Q

TSH, T4 and T3 levels in secondary hypothyroidism

A
  • Decrease in TSH

- Decrease in T4 and T3

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21
Q

Treatment for primary hypothyroidism

A

• Start with thyroxine (T4) 100 mg daily
○ Shorter symptomatic period
○ Unless elderly / ischaemic heart disease
□ Start 25 mg daily with increments 4-6 weekly
• Usual dose 100-150 mg daily
○ Some variation with body weight
• Aim normal FT4 without TSH suppression
○ Individual variation: may need fine tuning within reference ranges
• No evidence in properly conducted trials to support T4/T3 combination therapy

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22
Q

What is chronic autoimmune thyroiditis

A

Autoimmune thyroiditis, (or Chronic Autoimmune thyroiditis), is a chronic disease in which the body interprets the thyroid glands and its hormone products T3, T4 and TSH as threats, therefore producing special antibodies that target the thyroid’s cells, thereby destroying it

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23
Q

What is hashimoto’s disease

A

Hashimoto’s thyroiditis, also known as chronic lymphocytic thyroiditis, is the most common cause of hypothyroidism in the United States.

It is an autoimmune disorder in which antibodies directed against the thyroid gland lead to chronic inflammation

24
Q

How is the diagnosis of hashimoto’s made

A

The diagnosis of Hashimoto’s thyroiditis is often made when patients present with symptoms of hypothyroidism, often accompanied by the finding of a goiter (an enlarged thyroid gland) on physical examination, and laboratory tests consistent with hypothyroidism, an elevated serum TSH with low thyroid hormone (Free thyroxine) levels. Antibodies against TPO, when measured, are usually elevated.

25
Q

What is myxoedema (coma)

A
  • Accumulation of glycosaminoglycans in interstitial spaces of tissues
  • swelling of the skin and underlying tissues giving a waxy consistency, typical of patients with underactive thyroid glands.
    the more general condition associated with hypothyroidism, including weight gain, mental dullness, and sensitivity to cold.
26
Q

Symptoms of thyrotoxicosis

A
  • Weight loss
  • Lack of energy
  • Heat intolerance
  • Anxiety/irritability
  • Increased sweating
  • Increased appetite
  • Thirst
  • Palpitations
  • Pruritus
  • Weight gain
  • Loose bowels
  • Oligomenorrhoea
27
Q

Signs associated with thyrotoxicosis

A 
• Fine tremor
• Warm
• Sinus tachycardia
• Atrial fibrillation    
• Goitre
• Move when swallow
• Smooth / not
• Bruit / not
• Lid retraction / lid lag
• Proptosis / exophthalmos
• Ophthalmoplegia
○ Abnormal eye movements
○ Causes diplopia
• Inflammation (conjunctiva)
28
Q

Symptoms of thyroid eye disease (TED)/ thyroid associated ophthalmopathy (TAO)

A
  • Associated with autoimmune hyperthyroidism (Graves disease) in ~ 20% of patients
    • Graves and TED may not occur at the same time, or at all
  • Increased risk in smokers
  • Autoantibody mediated
  • Inflammation of all orbital tissues except the eye
    • Fat, muscles, conjunctiva, eyelids
  • CT scan imaging helpful
29
Q

Mild symptoms of thyroid eye disease

A
  • ‘Itchy’ / dry eyes
  • Artificial tears help
  • ‘prominent’ eyes/ changes in appearance
30
Q

Worrisome symptoms of thyroid eye disease

A 
• Diplopia / loss of sight
• Loss of colour vision
○ Grey  / blurred patches
• Redness / swelling of conjunctiva
• Unable to close eyes fully
Ache / pain / tightness in or behind eye
31
Q

Main cause of thyrotoxicosis

A
  • The main cause of thyrotoxicosis is hyperthyroidism, which is an overactivity of the thyroid gland resulting in it producing excess levels of thyroid hormones. If the hyperthyroidism is due to an autoimmune cause, it is called Graves’ disease.
  • Autoantibody stimulates the TSH receptor, causing excess thyroid hormone production and thyroid growth (goitre)
32
Q

Other causes of thyrotoxicosis

A
  • Toxic multinodular goitre
  • Toxic adenoma
  • Thyroiditis
  • Drugs (eg. amiodarone)
33
Q

What is gestational thyrotoxicosis

A

Gestational thyrotoxicosis is a rare occurrence during pregnancy and is usually due to Grave’s disease (see chapter on Grave’s disease).

Presentation is usually in the mid- to late-first trimester. In addition to hypermesis gravidarum, other symptoms are those exhibited in hyperthyroidism: heat intolerance, sweating, angina, tachycardia, nervousness, and moist, warm skin.

There can also be enlargement of the thyroid gland.

34
Q

What is a thyroid uptake scan

A

A thyroid scan is a type of nuclear medicine imaging. The radioactive iodine uptake test (RAIU) is also known as a thyroid uptake. It is a measurement of thyroid function, but does not involve imaging.

35
Q

Graves disease treatment options

A 
• Medical
• Radioiodine
• Surgery
• Symptom control
	• β-blockers (propranolol)
		○ Not if asthmatic
• Risks of no treatment
	• Symptoms worsening
	• Atrial fibrillation
		○ Stroke
	• Osteoporosis
		○ Fractures
36
Q

Medical therapy for graves disease

A 
• Carbimazole or propylthiouracil (PTU)
• 18 months – 2 years
• Titrate or block-replace
• Approx one third long term cure rate
• Two thirds relapse
	○ Usually first year
	○ Cannot predict in advance
37
Q

A rare side effect of medical therapy treatment for graves disease

A
  • Agranulocytosis
38
Q

Radioiodine treatment for graves disease

A

• RADIOACTIVE IODINE TREATMENT (I-131)
• Oral treatment, radioiodine concentrated in thyroid, radiation kills thyroid cells
• Medical therapy first till euthyroid
• Approx 40% risk permanent hypothyroidism after treatment
• Not if pregnant / breast feeding
• Need to avoid prolonged close contact with others for 1-2 weeks after treatment
○ Tricky if young children
• Not if severe thyroid eye disease
• Future pregnancies

39
Q

Features of surgical treatment for graves disease

A

• Sub-total thyroidectomy (“almost total”)
• Patients must be euthyroid pre-operatively
○ Medical therapy first

40
Q

Risks of surgery for graves disease

A 
○ Anaesthetic
○ Neck scar
○ Hypothyroidism
○ Hypoparathyroidism
○ Vocal cord palsy (recurrent laryngeal nerve damage)
41
Q

Treatment for a toxic adenoma or toxic multinodular goitre

A
  • Initial treatment: short term medical therapy (to control thyroid function tests)
  • Subsequent curative treatment: radioiodine
42
Q

Thyroid eye disease - treatment options

A

• Encourage smoking cessation
• Steroids
○ Pulsed IV methylpred / oral prednisolone
• Other immunosuppressive / steroid-sparing agents
• Radiotherapy

• Surgical treatment
○ Orbital decompression
○ Eyelid surgery

43
Q

What is a thyroid storm

A

Thyroid storm occurs when your thyroid gland, located at the base of your neck, releases large amounts of thyroid hormone suddenly.

Your systolic blood pressure may rise, while your diastolic plummets. Your heartbeat may speed up, and you may have difficulty breathing, and yellowing of the skin (jaundice).

44
Q

Does treatment for thyroid help eye disease

A

no

45
Q

What is thyroid storm usually secondary to

A

graves

46
Q

What can trigger a thyrotoxic crisis

A 
• Surgery (GA)
• Childbirth
• Acute severe illness
○ Infection
○ Trauma
○ Diabetic ketoacidosis
○ Stroke
○ Pulmonary embolus
47
Q

Features of thyroid storm

A 
• Multi-system
• Graves
○ Goitre, thyroid eye disease
• Hyperpyrexia
• CNS
○ Agitation, delirium
• Cardiovascular
○ Tachycardia >140 bpm
○ Atrial dysrhythmias
○ Ventricular dysfunction
○ Heart failure
• GI
○ Nausea & vomiting
○ Diarrhoea
○ Hepatocellular dysfunction
48
Q

Relationship between degree of elevation of thyroid hormone concentrations and distinguishing uncomplicated thyrotoxicosis from thyroid storm

A

• Degree of elevation of thyroid hormone concentrations does NOT distinguish uncomplicated thyrotoxicosis from thyroid storm

49
Q

Treatment for transient mild thyrotoxicosis

A

• Always resolves (1-2 m)
• b-blockers if required
• Isotope scan would be ‘cold’
- Anti-thyroid drugs will not work

50
Q

Treatment for longer hypothyroid phase

A
  • Longer hypothyroid phase (4-6 m)
  • 80% normal at 1 year
  • May require thyroxine treatment for a while
51
Q

When should you consider annual thyroid function tests

A

• Patient is pregnant / within 1 year post-partum
○ ­ risk T1 diabetes, FHx thyroid disease, smoker
• Patient has very tender thyroid
○ May be raised inflammatory markers
• Clinical thyroid status does not fit with lab results
○ Rapidly changing thyroid function tests
• No diagnostic features of Graves disease
• Current / recent treatment with immunomodulatory medication

52
Q

Other autoimmune endocrine diseases associated with autoimmune thyroid disease

A
  • Type 1 diabetes
  • Pernicious anaemia
  • Coeliac disease
  • Premature ovarian failure
  • Addison’s disease
53
Q

Syndromes associated with autoimmune thyroid disease

A
  • Turner syndrome

- Down’s syndrome

54
Q

Medication for other diseases

A
  • Lithium - inhibits thyroid hormone synthesis and secretion
  • Amiodarone
55
Q

Goitre nodules in euthyroid patients

A
  • Common
  • More common in iodine-deficient areas
  • May be multinodular
  • Usually nothing to worry about
56
Q

Thyroid nodules in euthyroid patients

A
  • Thyroid nodule in euthyroid patient
  • Must exclude thyroid cancer - 5%
  • Ultrasound scan characteristics helpful
  • Fine-needle aspiration biopsy for cytology

Year 2 - T2 Theme 1 (20 decks)

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