Primary hypothyroidism is generally considered a stable or gradually progressing condition requiring life-long thyroid hormone replacement therapy. It is not uncommon to observe hyperthyroidism reverse to hypothyroidism. However, there are few case reports in the literature of switching from hypothyroidism to hyperthyroidism.
We report a 32-year-old G2P2 female who developed hypothyroidism during her pregnancies in 2010 and 2014. She was treated with levothyroxine during both pregnancies which were otherwise uncomplicated, and remained euthyroid between pregnancies. Levothyroxine was discontinued in June 2015, one year after the birth of her second child.
After unsuccessful attempts to conceive a third child, she was diagnosed with hyperthyroidism in March 2016. Other than fatigue and weakness she felt well, and there was no thyroid associated orbitopathy. A thyroid scan demonstrated homogenous increased uptake, in keeping with Graves’ disease. However, as thyroid indices were not available at the time of the scan, and since subsequent thyroid indices in July 2016 were normal, the differential diagnosis would include recovering thyroiditis. A thyroid ultrasound revealed a heterogeneous, nodular and hypervascular gland of normal size. TSH receptor antibodies and anti-thyroid peroxidase antibodies were negative.
Conversions from primary hypothyroidism to hyperthyroidism have been infrequently reported. There are several possible explanations for such a phenomenon. Some patients can have concurrent Hashimoto’s disease and Graves’ disease; others can have Graves’ disease with swinging dominance between TSH-stimulating autoantibodies (TSAb) and TSH-blocking autoantibodies (TBAb). Thyroid hormone replacement, anti-thyroid drugs, and pregnancy can influence TSAb and TBAb levels.
Conclusion : It is important for clinicians to be aware of this clinical entity to allow for prompt diagnosis and treatment.
University of Alberta
Burnaby, British Columbia, Canada
Rui Chen a board certified internist and is currently in the 5th year of her residency training in endocrinology at the University of Alberta. She obtained her medical degree and completed her residency training in internal medicine at the University of British Columbia.
Endocrinologist, Assistant Clinical Professor
University of Alberta
Dr. Jennifer Jacquier is a board certified endocrinologist and is currently appointed as Assistant Clinical Professor in the Division of Endocrinology & Metabolism in the Faculty of Medicine and Dentistry at the University of Alberta