Endemic goitre — DTM&H MCQ

Correct answer: C — Endemic goitre from iodine deficiency

The correct answer is C, endemic goitre from iodine deficiency. The clinical picture (a large midline neck swelling in an adolescent living in a highland region far from the sea, eating a teff-based diet with minimal iodised salt) is the classic setting for iodine deficiency disorder, since iodine-poor soil in mountainous, non-coastal terrain leads to chronically low dietary iodine intake. Reduced iodine limits thyroid hormone synthesis, so free T4 falls and the pituitary compensatorily raises TSH; the resulting sustained TSH drive causes diffuse thyroid follicular hyperplasia, producing the visible goitre. This biochemical pattern (low free T4, high TSH) confirms primary hypothyroidism due to a failing, iodine-starved thyroid gland rather than a structural or neoplastic neck mass. Endemic goitre remains one of the most common preventable causes of thyroid enlargement and developmental impairment in iodine-deficient regions of the world. Why the other options are wrong: B. Thyroglossal cyst: presents as a smooth midline swelling that characteristically moves upward with tongue protrusion, and thyroid function is normal because it arises from a persistent thyroglossal duct remnant, not thyroid failure. A. Tuberculous lymphadenitis: produces matted, often lateral (not midline) cervical lymph nodes that may caseate and discharge, with systemic features of tuberculosis, and does not alter TSH or free T4. D. Lymphoma: causes firm, non-tender, progressively enlarging lymph node masses, often with systemic B symptoms, and thyroid biochemistry is typically normal unless the gland itself is directly infiltrated. E. Thyroid carcinoma: usually presents as a discrete, asymmetric, firm thyroid nodule rather than diffuse midline enlargement, and patients are typically euthyroid biochemically. Key point: A diffuse midline goitre with high TSH and low free T4 in a person from an iodine-poor, non-coastal highland area is diagnostic of endemic (iodine deficiency) goitre until proven otherwise.

Reference: WHO/UNICEF/ICCIDD, Assessment of Iodine Deficiency Disorders and Monitoring their Elimination: A Guide for Programme Managers, 3rd edition, World Health Organization, Geneva, 2007. https://iris.who.int