Explain 'Goitre'.

Goitre is an abnormal enlargement of the thyroid gland, appearing as a visible swelling at the front of the neck. The most common cause is iodine deficiency, which prevents the thyroid from producing adequate amounts of thyroid hormones (thyroxine and triiodothyronine). When these hormone levels drop, the pituitary gland responds by releasing more thyroid-stimulating hormone (TSH), causing the thyroid gland to enlarge as it attempts to compensate for the deficiency.

Iodine is an essential component of thyroid hormones, and without sufficient dietary iodine, the thyroid cannot function properly despite increasing in size. This condition is particularly common in regions where soil and water lack iodine, leading to insufficient iodine in the food chain. Symptoms beyond the visible neck swelling can include difficulty swallowing or breathing (if the goitre is large), hoarseness, and signs of hypothyroidism like fatigue, weight gain, and sensitivity to cold. Prevention is straightforward and cost-effective: consuming iodized salt ensures adequate iodine intake. In many countries, salt iodization programs have dramatically reduced goitre prevalence. Other causes of goitre include autoimmune diseases (like Hashimoto's thyroiditis or Graves' disease), nodules, or inflammation, but iodine deficiency remains the most preventable cause globally.