SN4 SHORT NOTE 5M ★ High-yield

Define goitre. Describe the causes and pathogenesis of simple and multinodular goitre.

Pathology · 2nd Professional — Para-Clinical

Definition

Goitre is enlargement of the thyroid gland from any cause. Simple (non-toxic) goitre results from impaired hormone synthesis with compensatory TSH-driven hyperplasia, and the patient is usually euthyroid.

Causes

Category	Causes
Endemic goitre	Iodine deficiency — when over 10% of a population is affected; classically the sub-Himalayan belt of India, and mountainous and flood-plain regions worldwide where soil iodine has been leached away
Goitrogens	Cassava, cabbage, cauliflower and other brassicas, soya, millet; drugs — lithium, amiodarone, antithyroid drugs, para-aminosalicylic acid
Sporadic goitre	Physiological demand in puberty and pregnancy; idiopathic
Dyshormonogenesis	Inherited enzyme defects of hormone synthesis; pendred syndrome adds sensorineural deafness
Other thyroid disease	Graves disease, Hashimoto thyroiditis, thyroiditis, neoplasm

Pathogenesis and Evolution

Impaired thyroid hormone synthesis — usually iodine deficiency → Falling T4 removes negative feedback → TSH rises → diffuse hyperplastic goitre — a symmetrically enlarged, soft, vascular gland with tall crowded follicular cells and scanty colloid → If the stimulus abates, follicles involute and fill with colloid — colloid goitre → Repeated cycles of hyperplasia and involution over years → multinodular goitre — nodules of unequal size with haemorrhage, fibrosis, calcification and cystic change; the gland becomes asymmetrical and irregular → Some nodules become autonomous → toxic multinodular goitre (plummer syndrome)

CLINICAL PEARL

Multinodular goitre is the scar of decades of intermittent stimulation. Follicles do not respond uniformly to TSH; some proliferate more, some involute, and the cycles superimpose. The nodularity is therefore not a neoplastic process but the accumulated record of repeated hyperplasia and involution — which is why haemorrhage, fibrosis and calcification are all present together in one gland.

Clinical Features and Complications

Usually euthyroid and asymptomatic, presenting as a cosmetic neck swelling that moves on swallowing
Pressure symptoms — dysphagia, stridor, hoarseness from recurrent laryngeal nerve involvement; retrosternal extension may cause superior vena caval obstruction, demonstrated by pemberton sign (facial congestion on raising the arms)
Sudden painful enlargement suggests haemorrhage into a nodule
Secondary thyrotoxicosis in about 10% over time
Malignancy — the overall risk in a multinodular goitre is low, but a dominant, hard, rapidly growing nodule must be investigated
In children, iodine deficiency causes cretinism — irreversible intellectual disability, deaf-mutism, short stature and a protruding tongue; and maternal deficiency impairs fetal neurodevelopment

Applied Aspects

Universal salt iodisation is one of India’s major public health successes, and has greatly reduced endemic goitre and cretinism; monitoring salt iodine content remains necessary
Investigations — thyroid function tests, ultrasound, and FNAC of any dominant or suspicious nodule; isotope scanning to identify autonomous "hot" nodules
Most simple goitres need no treatment; iodine or thyroxine may help early diffuse goitre but not established multinodular disease
Surgery for pressure symptoms, retrosternal extension, cosmetic concern or suspicion of malignancy; radioiodine for toxic nodular goitre
Beware the JOD–basedow phenomenon — giving iodine to a patient with long-standing nodular goitre containing autonomous nodules can precipitate thyrotoxicosis
Screen neonates for congenital hypothyroidism, since early thyroxine entirely prevents the neurological damage of cretinism — among the most cost-effective screening tests in existence

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