# A Rare and Unusual Evolution of Hypothyroidism in Hashimoto's Thyroiditis to Graves' Disease: A Case Report and Literature Review

## TL;DR

This paper reports a rare case where a man with Hashimoto's thyroiditis developed Graves' disease after years of thyroid hormone treatment.

## Contribution

The study highlights a rare transition between two thyroid conditions and suggests antibody dynamics and thyroid tissue status may influence this shift.

## Key findings

- Hashimoto's thyroiditis can transition to Graves' disease after long-term L-thyroxine treatment.
- Antibody predominance and residual thyroid tissue capacity may influence the shift between hypothyroidism and hyperthyroidism.
- Clinicians should consider Graves' disease in patients with persistent hyperthyroidism despite stopping L-thyroxine.

## Abstract

Our article examines a rare case where hypothyroidism due to Hashimoto's thyroiditis progressed, after a long period (three years) of L-thyroxine substitution, into confirmed hyperthyroidism due to Graves' disease in a 69-year-old man.

The article explores possible mechanisms of this unusual transition based on our case and others reported in the literature. Findings suggest that the coexistence of Hashimoto's thyroiditis and Graves' disease can lead to transitions between hypothyroidism and hyperthyroidism, influenced by the predominance of involved antibodies and residual capacity of thyroid tissue. The authors emphasize the importance of further studies to better understand these transitions and identify at-risk patients. In conclusion, the article highlights the necessity of considering the rare possibility of transition to Graves' disease in patients presenting with persistent hyperthyroidism despite cessation of L-thyroxine.