10 minute consultation: Newly diagnosed hypothyroidism
A 46 year old woman has returned to you for the results of blood tests. Two weeks earlier she had complained of increasing tiredness, constipation, dry skin, and weight gain. Thyroid function tests at her previous consultation showed concentrations of free levothyroxine (T4) of 7 nmol/l and of thyroid stimulating hormone (TSH) of 38 mU/l. Her mother had Graves ' disease and was treated with radioiodine ablation.
Underlying causes--The commonest cause of primary hypothyroidism is autoimmune thyroiditis. Hashimoto's thyroiditis is the combination of autoimmune thyroiditis and goitre; a positive test result for the thyroid autoantibodies antithyroglobulin and antiperoxidase will confirm the diagnosis. An enlarged, tender thyroid may indicate subacute thyroiditis.
Current and previous drug use--Amiodarone, lithium, interferon alfa, interleukin 2, macrophage colony stimulating factor, and oral and topical iodine are recognised causes of thyroid dysfunction. Check for history of thyroid surgery or head and neck irradiation and radioactive iodine therapy