A 16-year-old girl presents to her doctor complaining of a swelling in her neck which she has noticed in the last 2 weeks. She has felt more irritable although this is often transient. On examination, a diffuse swelling is palpated with no bruit on auscultation. The most likely diagnosis is:

A simple goitre (B) is an idiopathic enlargement of the thyroid. Often the condition is associated with thyroid antibodies, but these do not cause any symptoms. Riedel's thyroiditis (C) is a rare inflammatory disease of the thyroid gland that is characterized by fibrosis of the thyroid gland and other structures in the neck. It is often stony or woody on palpation and patients are usually asymptomdatic. The patient does not have any features of hypehyroidism (A) in which a thyroid bruit can be present. A thyroid cyst or nodule (D) is usually harmless and is a fluid-filled swelling often presenting s a single compressible small lump rather than a diffuse swelling. A full history and examination should always be conducted with ultrasound and fine needle examination to exclude malignancy.