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CEP > L14 - Thyroid > Flashcards

L14 - Thyroid Flashcards

1
Q

What is the function of thyroid hormones?

A
  1. Control of metabolism: energy generations and use
  2. Regulation of growth
  3. Multiple roles in development
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2
Q

Which thyroid hormone is the most biologically active one?

A

T3 is the biologically active hormone

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3
Q

What are the different thyroid hormone binding proteins?

A
  1. Serum albumin
  2. TBG (thyroxine binding globulin)
  3. Transthyretin
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4
Q

Which thyroid hormone has a greater percentage of being free?

A 
T4 = 0.03%
T3 = 0.3%
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5
Q

What would thyroid function tests show for hyperthyroidism?

A
  • LOW serum TSH (thyroid stimulatinf hormone)
  • HIGH serum free T4
  • HIGH serum free T3
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6
Q

What would thyroid function tests show for hypothyroidism?

A
  • HIGH serum TSH (thyroid stimulating hormone)
  • LOW serum free T4
  • LOW serum free T3
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7
Q

Which gender is thyroid disease more prevalent in?

  • Hyperthyroidism
  • Hypothyroidism
  • Goitre
A

Female more common than men

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8
Q

What are the different possible aetiologies of hyperthyroidism?

A
  1. Graves’ hyperthyroidism (AI disorder)
  2. Toxic nodular goitre (single or multinodular)
  3. Thyroiditis (silent, subacute): inflammation
  4. Exogenous iodine (external origin)
  5. Factitious (taking excess TH)
  6. TSH secreting pituitary adenoma
  7. Neonatal hyperthyroidism
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9
Q

What are some symptoms of HYPERthyroidism?

A
  • Tachycardia
  • Heat sensitivity
  • AF
  • Shortness of breath
  • Tremor
  • Myopathy (muscle weakness)
  • Weight LOSS
  • INC appetite
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10
Q

What is Graves’ disease?

A
  • AI disorder
  • Most prevalent AID in UK and US
  • Pathogenetic antibodies to TSH receptor on thyroid follicular cells (long acting thyroid stimulators)
  • Interplay between genetic and environmental factors
  • Environmental factors include: gender, stress, infection, pregnancy or drugs
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11
Q

What are some symptoms of graves disease?

A
  • Anxiety and irritability
  • Heat sensitivity
  • Weight loss despite normal eating habits
  • Goitre (enlargement of thyroid gland)
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12
Q

What are the different possible extra-thyroidal manifestations of the eye from Graves’ disease?

A
  • Lid lag/ retraction
  • Conjunctival oedema
  • Periorbital puffinesss around the eye
  • Proptosis (bulging)
  • Ophthalmoplegia (weakness of eye muscles)
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13
Q

What are the different possible extra-thyroidal manifestations of the skin from Graves’ disease? (Dermopathy)

A
  • Pretibial myxoedema

- Acropachy

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14
Q

What is pretibial myxoedema?

A
  • Localised lesions of the skin
  • Pretibial meaning myxoedema on the shins (result in swelling and lumpiness)
  • Myxoedema is the deposition of hyaluronic acid
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15
Q

What is acropachy?

A
  • Thickening of extremities
  • Swelling and clubbing of fingers and toes
  • Periostitis (inflammation of periosteum; the CT surrounding bone); most commonly the metacarpal bones
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16
Q

What causes neonatal hyperthyroidism?

A
  • TSH-R antibodies cross the placenta
  • Need to control hyperthyroidism in mother during pregnancy
  • Mother has or had Graves’ disease
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17
Q

What are the different treatment options for HYPERthyroidism?

A
  1. Antithyroid drugs to block hormone synthesis
  2. Surgical removal of thyroid
  3. Radioiodine (131I) therapy
18
Q

What are some of the different anti-thyroid drugs (thionamides)

A
  1. CARBIMAZOLE (methimazole)

2. PROPYLTHIOURACIL

19
Q

How does propylthiouracil work?

A

Block iodine incorporation and organification through inhibition of thyroperoxidase

20
Q

What would you need to consider before giving thionamide therapy?

A
  1. Rapid control, well tolerated
  2. Side effects
    - Rash, joint pains, sickness
    - Agranulocytosis: no WBC, infection risk
    - Liver disease
  3. Low cure rate
    - (30-40% lower in men)
21
Q

What would surgery involve when treating hyperthyroidism?

A

Total thyroidectomy: removal of whole thyroid gland

22
Q

What are the complications of total thyroidectomy?

A
  1. Hypothyroidism
  2. Hypoparathyroidism: problems with calcium
  3. Recurrent laryngeal nerve damage
  4. Bleeding
  5. Thyroid storm: release of high concentrations of TH in circulation
23
Q

What would radioactive iodine treatment for hyperthyroidism involve?

A
  • Capsule (fixed dose)
  • Highly effective (85% cure)
  • Usually pre-treatment with drugs
  • May worsen eye disease (treat with steroids)
24
Q

What are the possible risks of giving iodine-131?

A
  1. Hypothyroidism (~60%)
  2. Cancer
  3. Infertility
  4. Teratogenesis (contra-indicated in pregnancy and breastfeeding - congenital malformations are produced in the embryo or foetus)
25
Q

What are the treatment aims of hyperthyroidism?

A
  • To relieve symptoms
  • To restore T3 and T4 values within normal range
  • To obtain long-term normal thyroid function
26
Q

What is the prognosis of patients after hyperthyroidism treatment?

A
  • 30% of patients with Graves’ disease have normal thyroid function long-term following drugs
  • 131-I and surgery assoc with >50% risk of long-term hypothyroidism
27
Q

What are the different possible aetiologies of HYPOthyroidism?

A
  1. Autoimmune - Hashimoto’s thyroiditis (TPO and Tg antibodies - genetic predisposition)
  2. After treatment for hyperthyroidism
  3. Subacute/ silent thyroiditis
  4. Iodine deficiency
  5. Congenital (thyroid agenesis/ enzymes defects)
28
Q

What is the main source of iodine in the UK?

A

From milk and dairy products

29
Q

Which group of people are more likely to suffer from iodine deficiencies?

A

Vegans

30
Q

What is cretinism?

Causes?

A
  • Congenital HYPOthyroidism (underactivity of thyroid gland at birth)
  • Deficiency of iodine in mother’s diet during pregnancy
  • Growth retardation
  • Developmental elay
  • Abnormal features
31
Q

What are some symptoms of HYPOthyroidism?

A
  • Bradycardia
  • Heart failure
  • Pericardial effusion (abnormal acc of fluid in the pericardial cavity –> inc intrapericardial pressure –> negatively affect heart function)
  • Weight gain
  • Constipation
  • Myxoedema
  • Vitiligo
  • Cold intolerance
32
Q

What tablet is typically prescribed for hypothyroidism?

A

LEVOTHYROXINE

33
Q

What is the goal of therapy for hypothyroidism?

A
  • Restore patients to euthyroid state

- Normalise serum T4 and TSH concentrations

34
Q

What would you do in an investigation of thyroid nodules/ goitre?

A
  1. Assessment of thyroid function
    - Serum TSH
    - Serum free T3/T4
  2. Assessment of thyroid size
    - Symptoms
    - X-ray thoracic inlet
    - CT or MRI of neck
    - Respiratory flow loop
  3. Assessment of thyroid pathology
    - Radionuclide scanning (radioisotope scan)
    - Ultrasound scanning
    - Fine needle aspiration cytology
35
Q

Describe what the expiratory respiratory flow loop would look like if there was an intrathoracic obstruction

A
  • Expiratory plateau
36
Q

Describe what the inspiratory respiratory flow loop would look like if there was an extrathoracic obstruction

A
  • Inspiratory plateau
37
Q

Why can respiratory flow loops be used to assess thyroid size?

A
  • The thyroid gland lies close to the boundary between extra and intra-thoracic sections of the trachea
  • If large goitre –> press against trachea –> cause narrowing/ deviation of upper airway –> experience difficulty in breathing or shortness of breath
38
Q

What is the role of ultrasound scanning when investigating the thyroid gland?

A
  • Differentiation of solid from cystic nodules
  • Differentiation of single from multiple nodules (superior to palpation)
  • Criteria suggestive of malignancy (irreg margin, calcifications, solid, hypo-echoic)
  • Guidance of fine needle aspiration
39
Q

What are the different possible aetiologies of thyroid cancer?

A
  1. External irradiation
  2. Iodine deficiency
  3. Oncogene expression
  4. Genetic factors
40
Q

What are the different possible managements of thyroid cancer?

A
  1. Surgery
    - Total thyroidectomy
    - Partial thyroidectomy (lobectomy)
  2. Radioiodine ablation
  3. Thyroxine suppression
  4. Measurement of serum thyroglobulin

CEP (16 decks)

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