Endocrine Abstracts

We report the case of a 41-year-old lady who developed severe thyroid eye disease on a background of long standing hypothyroidism. She had been diagnosed with autoimmune hypothyroidism 15 years previously with positive TPO antibodies. She had been successfully maintained on levothyroxine replacement since then. She presented with a four year history of progressive eye swelling, gritty eyes and diplopia. On examination she was found to have active thyroid eye disease with restriction of extra-ocular movement, proptosis and diplopia. In addition her thyroid function tests showed suppressed TSH indicating probable over replacement with thyroid hormone. Her levothyroxine dose was weaned and eventually discontinued. She proceeded to have a course of steroids with some reduction in her visual symptoms. Unfortunately, she developed significant symptoms of thyrotoxicosis off thyroid replacement. Thyroid uptake scan showed generally increased uptake in the right lobe with no evidence of a nodule on ultrasound. TSH receptor antibodies at this time were strongly positive. Unfortunately her eye disease relapsed and she required orbital decompression surgery to which she had a good functional and cosmetic response. Thyroid function normalised rapidly on carbimazole and she was able to discontinue treatment after nine months. Following a period where she was biochemically euthyroid TSH levels have begun to rise again. We postulate that this lady had TSH receptor antibodies which were variably stimulating or blocking the TSH receptor as an underlying cause for her presentation. This case highlights the need to consider thyroid eye disease in a patient presenting with visual symptoms and a history of autoimmune thyroid disease. It also illustrates the need to have a high index of suspicion for possible conversion of hypothyroidism to hyperthyroidism in a patient rather than attributing the biochemical abnormality solely to over replacement with thyroid hormone.