Goitre and Endemic Goitre
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Direct answer
Goitre is any enlargement of the thyroid gland, and endemic goitre is goitre caused by iodine deficiency across a population. Inadequate iodine limits thyroid hormone synthesis and raises TSH, driving diffuse hyperplasia that becomes multinodular over time. Iodised salt is the main preventive measure under India's national programme.
What you must remember
- Goitre: any thyroid enlargement, which may be diffuse, multinodular or a solitary nodule.
- Endemic goitre: iodine deficiency, the commonest cause in endemic regions, with thyroid hyperplasia driven by a raised TSH.
- Iodine programme: universal iodised salt is the main prevention under the National Iodine Deficiency Disorders Control Programme.
- Goitrogens: thiocyanates from foods such as cassava, and drugs such as lithium, interfere with iodine uptake or hormone release.
- Retrosternal goitre: extension below the thoracic inlet, causing tracheal compression with stridor and dysphagia.
- Pemberton sign: facial plethora, stridor or dyspnoea when the arms are raised, indicating thoracic inlet obstruction.
- Malignancy clues: a firm solitary nodule, cervical lymphadenopathy, hoarseness or a fixed mass raise suspicion and need cytology.
Where the exam tries to catch you
Most lost marks come from calling a goitre benign on thyroid function alone, or from missing airway compression.
- Trap: Calling every goitre with a normal TSH benign. Correct: Solitary or firm nodules still need ultrasound and fine needle aspiration cytology, because thyroid cancer can occur in a euthyroid patient.
- Trap: Ignoring airway symptoms in retrosternal goitre. Correct: Stridor, dysphagia or the Pemberton sign signal compression, and surgery is considered when symptoms are significant.
- Trap: Treating endemic goitre with thyroxine in every case. Correct: Iodine supplementation and salt iodisation come first, and thyroxine is used selectively rather than routinely.
Frequently asked questions
What is the main cause of endemic goitre?
Iodine deficiency is the main cause of endemic goitre, because inadequate iodine limits thyroid hormone synthesis and raises TSH. Chronic TSH stimulation enlarges the gland, and long-standing disease often becomes multinodular.
How does iodised salt prevent endemic goitre?
Iodised salt supplies iodine to populations with deficiency, restoring thyroid hormone synthesis and reducing TSH stimulation of the gland. India's National Iodine Deficiency Disorders Control Programme relies on universal salt iodisation as its principal preventive measure.
What symptoms suggest retrosternal goitre compression?
Stridor, dyspnoea, dysphagia and hoarseness suggest compression of the trachea, oesophagus or recurrent laryngeal nerve by a retrosternal goitre. The Pemberton sign, in which facial plethora and stridor appear on raising the arms, also indicates thoracic inlet obstruction.
When is fine needle aspiration cytology needed in a patient with goitre?
Fine needle aspiration cytology is needed for a solitary or dominant thyroid nodule, especially a firm, rapidly growing or sonographically suspicious one. It helps separate benign colloid nodules from thyroid carcinoma before surgery is planned.