Endocrine Abstracts

JOINT2130

Introduction: Autoimmune thyroid disorders can present atypical evolutions making their management complex. We report the case of a young patient presenting an unusual alternation between phases of hyperthyroidism and hypothyroidism.

Observation: A 26-year-old patient presented with primary hypothyroidism in the 4th month of her pregnancy, treated with L-thyroxine. She consulted 6 months after giving birth for asthenia, palpitations, and tremors. The biological assessments showed a suppressed TSH and elevated FT4. Anti Thyroid peroxidase antibodies and Anti-TSH receptor (ATSHR) antibodies were positive. L-thyroxine was interrupted and treatment with thiamazole was started. Three years later, biological hypothyroidism was objectified leading to the discontinuation of thiamazole. The patient presented at 12 weeks of pregnancy. She was still in clinical and biological euthyroidism. ATSHR antibodies had returned negative. Six months after delivery, a thyroid assessment revealed the reappearance of hyperthyroidism. A thyroid scintigraphy was performed, showing normal and homogeneous thyroid uptake. The diagnosis of autoimmune thyroid disease with swing antibodies was retained and the decision was to put the patient on low-dose thiamazole each time she presented a phase of hyperthyroidism.

Discussion: The initial positivity of ATSHR antibodies points towards Graves’ disease, but a normal scintigraphy does not support this diagnosis, nor does the evolution with oscillation between hyperthyroidism and hypothyroidism. This oscillation could be related to a dynamic evolution of autoimmunity, with fluctuations of ATSHR antibodies between stimulating and blocking forms. There is also evidence that Graves’ disease and Hashimoto’s thyroiditis may be different manifestations of a continuous spectrum of autoimmune thyroid diseases.