A 39-year-old woman presented with a large, painless swelling in her neck. The enlargement had been a gradual process over 2 years. She had no other symptoms and felt generally well. On examination, her thyroid was diffusively enlarged and had a rubbery consistency. There were no signs of thyrotoxicosis or of thyroid failure.
Thyroid function tests showed that she was euthyroid; T3 was 1.2nmol/l (NR 0.8-2.4), T4 was 12nmol/l (NR 9-23) and TSH was 6.3mU/l (NR 0.4-5mU/l). However, her serum contained high titre antibodies to thyroid peroxidase (1/64000; 4000iu/ml).
This patient had Hashimoto's thyroiditis. The goitre was huge, and she was treated by partial thyroidectomy; the goitre did not recur, and the patient has remained euthyroid for 12 years.