Endocrine Abstracts

A 24 years old veterinary nurse presented to the cardiology outpatient clinic with palpitations, breathlessness and lethargy. There was no history of weight loss. She had a past history of bulimia. She was clinically euthyroid. ECG demonstrated sinus tachycardia with heart rate of 120 bpm. Thyroid functions test (TFT) done by GP was normal. She was initially treated with beta-blockers.

She was subsequently admitted to hospital a month later with palpitations, breathlessness and intermittent chest pain. She was tremulous, had a small goitre but no eye sign. Repeat TFT at this time were as follows: FT3 >46, FT4 >75 and TSH 0.01. She was started on carbimazole 5 mg tds and propranolol 80 mg bd and referred to the endocrine clinic as an outpatient.

In clinic six weeks later, her FT4 remained greater than 75. The patient admitted that she was omitting carbimazole on occasions and the dose was increased to 60 mg od.

After a further six weeks FT4 remained markedly elevated at 155, with undetectable TSH. Anti-TPO and anti-TSH receptor antibodies were negative. US scan of her neck showed normal size and echotexture of the thyroid gland.

There was a suspicion of factitious thyrotoxicosis and that she was taking thyroxine surreptitiously. A thyroid uptake scan showed no uptake of technetium.

Although a negative thyroid uptake scan can occur in thyroiditis, the prolonged period of thyrotoxicosis suggested a diagnosis of factitious thyrotoxicosis.

This case illustrates the importance of physicians correlating biochemical findings with clinical features and considering other causes of thyrotoxicosis when patients fail to respond to treatment