Endocrine Abstracts

A 39-year-old lady with background history of autoimmune hypothyroidism diagnosed over 10 years ago, established on Levothyroxine 100 mg once daily, was referred by the GP with unusual sweating, palpitations, tiredness, anxiety, tremors and weight loss of around one stone over last few months. The thyroid function tests were suggestive of thyrotoxicosis with TSH of less than 0.05 mu/land FT4 60 pmol/l, hence the dose of levothyroxine was gradually reduced and ultimately stopped. Despite all this she remained symptomatic. She was commenced on Carbimazole 20 mg once daily and Propranolol 40 mg thrice daily. Her symptoms gradually improved. On examination there was no goitre or signs of thyroid eye disease. She had family history of thyroid disease. The thyroid uptake scan and the TRAb result which was available later (raised at 24 U/l) confirmed autoimmune Graves’ disease. She had radioactive iodine therapy (530 MBq), following which she developed of thyroiditis with thyroid gland swelling and painful swallowing. She was started on tab Prednisolone 30 mg once daily for five days which improved her symptoms. When she was reviewed again after five weeks, the TFTs were suggestive of hypothyroidism (TSH of 131.5 mu/l, FT4 less than 1 pmol/land FT3 1.6 pmo/l), hence she was started on tab Levothyroxine 100 mg once daily. She was closely monitored with repeat TFTs and over a period of 4-6 weeks her TFTs improved significantly (TSH 1.69 mu/l, FT3 4.5 and FT4 19 pmol/lrespectively). She still complained of tiredness and low energy levels, hence vitamin D level was done which was very low and she was started on replacement. We explained to her that around 10% of patients with hypothyroidism still have symptoms of feeling tired and lethargic despite achieving target range of FT4, FT3 and TSH level. For completion purpose she was referred to rheumatologist to look into the possibility of fibromyalgia causing her symptoms.

Conclusion: This case highlights the fact that occasionally patients labelled with diagnosis of hypothyroidism may actually have blocking thyroid antibodies, and later they may present as thyrotoxicosis when producing stimulating antibodies. Hence physician or GP need to be aware of this switching antibodies in Graves’ disease to manage the patient properly and prevent any thyrotoxicosis related complications. Such cases are clinically challenging hence block and replace regimen is ideal until definitive treatment is done.