Goitre

Non-toxic goitre: any benign, non-inflammatory enlargement of the thyroid gland that is not associated with hyperthyroidism

Non-toxic multinodular goitre

Epidemiology
- Most common cause of non-toxic goitre in non-iodine deficient countries
- Incidence about 5%
Risk factors
- Can be associated with iodine deficiency
- Genetic
- Smoking
- Autoimmune disease
- Malignancy
Aetiology
- Chronic autoimmune thyroiditis
- Graves
- Tumours
- Thyroiditis
- Infiltrative diseases
- TSH secreting pituitary tumours
- Thyroid hormone resistance
Pathophysiology
- True pathophysiology is not known very well
- Impaired synthesis of thyroid hormone - leads to compensatory rise in serum TSH, which results in repeated instances of stimulation and involution of thyroid follicular cells
- Macrofollicular nodules - a combination of monoclonal adenomas and colloid nodules
- Microfollicular adenomas are follicular neoplasms which can only be differentiated from follicular carcinomas by their lack of capsular or vascular invasion

Epidemiology
- In iodine-deficient populations, a palpable goitre can be detected in 40-90% of patients
- Incidence increases by age due to its environmental aetiology
Aetiology
- Dietary iodine deficiency (only known cause)
Pathophysiology
- Persistent TSH stimulation leads to diffuse follicular epithelial hyperplasia
- Associated with chronic untreated hypothyroidism and cretinism (actually a much bigger problem than the local symptoms)
Management
- Iodine supplementation

Majority are asymptomatic and euthyroid
Consider symptoms of hypothyroidism (fatigue, constipation, cold intolerance) and hyperthyroidism (palpitations, dyspnoea on exertion, unexplained weight loss)
Obstructive symptoms? (exertional dyspnoea (requires trachea<8mm)/dyspnoea positional or nocturnal/wheezing/cough/stridor/OSA)
Dysphagia/voice changes
- Vocal cord compression from RLN paralysis is extremely rare - vocal cord dysfunction should raise the concern for malignancy harboured within the goitre

Advantages and disadvantages of the treatment options in nontoxic multinodular goiter

	Advantages	Disadvantages
Surgery	Significant goiter reduction Rapid decompression of trachea Prompt relief of symptoms Definite histologic diagnosis	Inpatient High cost Surgical risk Vocal cord paralysis: approximately 1% Hypoparathyroidism: approximately 1% Risk of hypothyroidism dependent of resection Risk of recurrence dependent of resection
Radioiodine	Most often outpatient If outpatient: low cost Few subjective side effects Goiter reduction: 50% within one year Improves inspiratory capacity in long term Can be repeated successfully	Limitation of administrated radioactivity Restricted proximity to other persons Contraceptives needed in fertile women Gradual reduction of the goiter Decreasing effect with increasing size Small risk of acute goiter enlargement Risk of thyroiditis: 3% Risk of transition into Graves' disease: 5% One-year risk of hypothyroidism: 15 to 20% Long-term cancer risk unknown
Levothyroxine	Outpatient Low cost May prevent new nodule formation	Low efficacy Lifelong treatment Adverse effects (bone, heart) Not feasible when TSH is suppressed

Observation

TSH suppression

Goitre size reductions in about 30% of patients
Balance ease of intervention with risks of lifelong subclinical hyperthyroidism on heart and bones

Radio-iodine ablation (RAI)

Surgery

Indications
- Absolute
  - Obstructive symptoms without other cause
  - Tracheal compression
  - Suspected or proven malignancy as per Bethesda, where appropriate surveillance would be hampered
  - Substernal extension
  - Patient preference (assuming they are an appropriate candidate)
Extent of surgery
- Tailor to patient - whether to take both lobes or just one
- Prefer total thyroidectomy in patients with evidence of bilateral goitre, positive family history thyroid disease, patients on thyroid hormone supplementation
- Subtotal thyroidectomy associated with up 50% recurrence
- Subtotal may be favoured in patients that will struggle to take medication
Pre-op assessment
- TSH
- CT/MRI
  - Likely to be resectable through standard cervical incision if the goitre extends inferiorly only as far as the superior aspect of the aortic arch
  - Those extending further, extending posteriorly, and/or crossing the midline from the dominant side are significantly more difficult and likely to require sternal split and partial or even total median sternotomy
- Flow-volume loop if ?upper airway obstruction
- ?FNA if malignancy suspected
- Fibre-optic intubation may be necessary if marked tracheal deviation