- Endemic Goiter, also known as Multinodular Goiter, is the presence of a goiter caused by nutritional deficiency of Iodine. As table salt is now supplemented with iodine, endemic goiter is almost never observed except in on some occasions in developing countries.
- Nutritional deficiency of Iodine results in decreased capacity of the thyroid gland to produce thyroid hormones. Reduced circulating levels of thyroid hormones release negative feedback on hypothalamic secretion of TSH, resulting in increased TSH release. As discussed in Thyroid Hormone Regulation TSH is a trophic factor for the thyroid gland and increased levels of TSH result in diffuse hypertrophy of thyroid glandular tissue which manifests grossly as a goiter.
- Gross Appearance
- Diffuse thyroid gland hypertrophy can be visibly observed as a goiter of the neck.
- Histological Appearance
- Initially, endemic goiters appear as symmetric hypertrophy and hyperplasia of well-differentiated thyroid follicles. However, repeated bouts of iodine deficiency over a lifetime may eventually result in irregular hypertrophy and hyperplasia that manifests as nodularity in the thyroid glandular tissue.
- Because Endemic Goiter is ultimately caused by reduced thyroid hormone levels it is accompanied by the clinical syndrome of hypothyroidism. Although the goiter itself is usually of cosmetic concern, it may impinge on local structures causing dysphagia or airway obstruction. Irregular, nodular goiters due to repeated bouts of iodine deficiency may progress to thyroid follicular carcinoma.