A condition in which the whole of the THYROID GLAND is diffusely enlarged and firm. It is one of the diseases produced by AUTOIMMUNITY. The enlargement is due to diffuse infiltration of LYMPHOCYTES and an increase of fibrous tissue. This form of GOITRE appears in middle-aged women, does not give rise to symptoms of thyrotoxicosis (see THYROID GLAND, DISEASES OF – Thyrotoxicosis), and tends to produce myxoedema (see THYROID GLAND, DISEASES OF – Thyroiditis).