Poster Presentation Annual Meetings of the Endocrine Society of Australia and Society for Reproductive Biology and Australia and New Zealand Bone and Mineral Society 2016

A rare case of alternating hyperthyroidism and hypothyroidism in Graves' disease (#423)

Mimi Wong 1 , Warrick Inder 1 2
  1. Department of Diabetes and Endocrinology, Princess Alexandra Hospital, Brisbane, QLD, Australia
  2. School of Medicine, University of Queensland, Brisbane, QLD, Australia

Background: Graves’ disease is usually associated with hyperthyroidism. Alternating hyperthyroidism and hypothyroidism in Graves’ disease is a very rare phenomenon, thought to be due to a change from stimulating to inhibitory TSH receptor antibodies (TRAb). We present a case of spontaneously oscillating thyroid function over a 14 year period.

Case Presentation: A 37 year old female was diagnosed with Graves’ disease in 2002. At the time of her diagnosis she was hyperthyroid and was initially managed with carbimazole. Her thyroid function tests (TFTs) then showed a T4 of 25 pmol/L (10–20), T3 of 11.8 pmol/L (2.5–6.8) and TSH <0.05 mU/L (0.4–4.0), along with a TRAb level of 35 U/L (<1). Later, in 2007 she became spontaneously hypothyroid, her TSH increased to 100 mU/L, T4 was 10 pmol/L, T3 was 2.8 pmol/L and her TRAb level decreased to 3.2 U/L. She then was commenced on thyroid hormone replacement, consisting of a combination of thyroxine and thyroid extract, and remained quite stable whilst on it until in 2015, when she developed symptoms of hyperthyroidism again. Her TFTs then revealed a T4 of 29 pmol/L, T3 of 12.2 pmol/L, TSH <0.05 mU/L and TRAb level of 8 U/L. Although initially the total dose of thyroid hormone replacement was reduced and the form changed to oral T3, her hyperthyroidism persisted and the thyroid hormone replacement was ceased. She was subsequently commenced on carbimazole again, and referred to our institution at this point. There has been a notable improvement in her TFTs: T4 16 pmol/L, T3 7.0 pmol/L and TSH <0.05 mU/L, but issues with poor adherence to the carbimazole have prevented complete normalisation.

Conclusion: Oscillating thyroid function in Graves’ disease is very rare. Definitive treatment with radioactive iodine or surgery with subsequent thyroxine replacement has been recommended for long term management.