Define Goitre & Multinodular Goitre. Describe its clinical features and complications.

The Concept & Classification

A goitre is simply an enlargement of the thyroid gland, and the many causes become manageable if classified along two axes: whether the gland is diffusely enlarged or nodular, and whether it is toxic (overactive) or non-toxic. This grid organises the whole subject.

How a Simple Goitre Becomes Multinodular

Understanding the natural history explains most nodular goitres. Iodine deficiency (or increased demand at puberty/pregnancy) lowers thyroid hormone output, so the pituitary secretes more TSH, which drives diffuse hyperplasia — a soft, smooth simple goitre. Over years of fluctuating stimulation and involution, the gland becomes nodular (multinodular goitre), with some nodules eventually becoming autonomous (toxic MNG) and others developing haemorrhage, cystic change or calcification. This is why endemic (iodine-deficient) regions have so much goitre, and why simple goitres evolve into nodular ones.

Clinical Features

A goitre is a neck swelling that characteristically moves upwards on swallowing (because the thyroid is bound to the larynx by the pretracheal fascia) — the sign that identifies it as thyroid. Examination assesses its size, surface (diffuse or nodular), consistency, lower border (whether it can be felt, or extends retrosternally), any tracheal deviation or compression, cervical nodes, a bruit, and the patient's thyroid status.

Complications

These are high-yield and follow from a mass in the neck:

• pressure effects — dysphagia (oesophagus), dyspnoea and stridor (tracheal compression), and hoarseness (recurrent laryngeal nerve)
• retrosternal extension causing thoracic-inlet obstruction
• secondary thyrotoxicosis (toxic change)
• malignant change
• haemorrhage into a nodule, causing sudden painful enlargement that may acutely compress the airway.

Investigations & Management

Investigate with thyroid function tests, ultrasound, FNAC of any dominant/suspicious nodule, and CT (without iodinated contrast if radioiodine may be needed) to assess retrosternal extension and tracheal compression. A non-toxic simple goitre is usually observed (correcting iodine deficiency). Surgery (total or subtotal thyroidectomy) is indicated for pressure symptoms, retrosternal extension, cosmetic concern, suspected malignancy, or toxic change; toxic goitres are additionally managed with antithyroid drugs or radioiodine.

The Thyroiditides

• Several forms of thyroiditis cause a diffuse goitre and are worth distinguishing.
• Hashimoto's thyroiditis is an autoimmune condition causing a firm diffuse goitre and eventual hypothyroidism (and carries a small risk of thyroid lymphoma).
• De Quervain's (subacute) thyroiditis is a painful goitre following a viral infection, with a transient thyrotoxic phase and a raised ESR, that is usually self-limiting.
• Riedel's thyroiditis is a rare, dense fibrosis producing a hard, fixed ('woody') gland that mimics cancer and can compress adjacent structures.

Retrosternal Goitre

A retrosternal (substernal) goitre is one that extends behind the sternum into the mediastinum, usually as a lower extension of a multinodular goitre. It matters because the confined thoracic inlet means it readily causes tracheal compression and venous obstruction (revealed by Pemberton's sign). It is an indication for surgery, and although it looks alarming, the great majority can be delivered through a standard neck (cervical) incision.

Assessment of Thyroid Status & Airway

Any goitre is assessed for two practical things beyond its size: the patient's thyroid status (euthyroid, hypothyroid or thyrotoxic — because a toxic goitre must be controlled before surgery) and the airway. Longstanding large goitres, especially retrosternal ones, may compress or deviate the trachea and, over time, weaken the tracheal cartilage rings (tracheomalacia), which can collapse when the supporting goitre is removed. Pre-operative assessment therefore includes flow-volume loops or CT where compression is suspected, and the anaesthetist is forewarned, because airway management is the key peri-operative risk in large goitre surgery.

Hashimoto's & the Risk of Lymphoma

Hashimoto's thyroiditis deserves a further note because, besides being the commonest cause of hypothyroidism and a firm diffuse goitre, it carries a small but definite risk of primary thyroid lymphoma. A rapidly enlarging goitre in a patient with known Hashimoto's should therefore raise this suspicion and prompt biopsy, illustrating how a benign autoimmune goitre can occasionally harbour a serious complication.

Retrosternal extension causes tracheal compression and needs assessment.

• Goitre = thyroid enlargement; classify as diffuse vs nodular and toxic vs non-toxic; moves up on swallowing.
• Iodine deficiency → ↑TSH → diffuse hyperplasia (simple goitre) → over years → multinodular goitre → can become toxic.
• Complications: pressure (dysphagia, stridor/dyspnoea, hoarseness), retrosternal extension (Pemberton's sign), toxic change, malignancy, haemorrhage into a nodule.
• Investigate: TFTs, ultrasound, FNAC of dominant nodule, CT for retrosternal/tracheal compression.
• Surgery for pressure symptoms, retrosternal extension, cosmesis, suspected malignancy or toxic change.