Mrs JA, a 41-year-old part-time nurse presented to her GP with a 6-month history of weight loss of 10 kg. On questioning she was eating well but complained of diarrhoea. She had also noticed that she felt exhausted and had developed insomnia. On further questioning she admitted to feeling increasingly hot and shaky and to having muscle weakness of the legs, particularly climbing stairs. She was normally well and had not seen the doctor since her last pregnancy 8 years before. A blood test showed the following results: free T₄ 49.7pmol/L; total T₄ 225 nmol/L; TSH <0.01 mU/L.

She was referred to an endocrinologist at the local hospital where initial investigations confirmed a diagnosis of Graves’ disease. She was treated with carbimazole and propranolol for the first month of treatment followed by carbimazole alone. Subsequently, after discussing the therapeutic options, she opted to have ¹³¹I therapy which was given as an outpatient when she had become euthyroid. She was followed up at regular outpatient visits and 6 months later complained of lethargy, weight gain and feeling cold all the time. Clinically she had features of hypothyroidism and blood tests were as follows: free T₄ 4.5pmol/L; TSH 25.7mU/L. The endocrinologist commenced thyroid hormone replacement therapy and 3 months later she was well and her blood tests were normal.