SAT-315 - Cyclic graves (alternating Hyper and hypothyroidism), a rare variant of Graves'

Background

Cyclic Graves’ disease is a rare variant of Graves’ disease characterized by alternating hyperthyroid and hypothyroid states. This phenomenon is believed to result from fluctuating levels of thyroid-stimulating and thyroid-blocking autoantibodies, leading to unpredictable thyroid hormone production. These fluctuations create diagnostic and therapeutic challenges and impose a substantial disease burden.



Case Presentation

A 69-year-old male with hypertension, diastolic dysfunction, vitamin D deficiency, and basal cell carcinoma presented with chest pain, palpitations, fatigue, and intermittent tremor. Examination revealed anxiety and tremulousness. Laboratory evaluation demonstrated suppressed TSH < 0.01 mIU/L, elevated free T4 2.7 ng/dL, and T3189 ng/dL. Thyroid autoantibodies were markedly elevated with TSI 170% and TRAb 28.93 IU/mL. Ultrasound demonstrated a multinodular thyroid with a dominant 2.5 cm left TR4 nodule.

The patient started methimazole with initial improvement. Two months later he developed overt hypothyroidism with TSH 71.4 mIU/L, free T4 0.27 ng/dL. This prompted methimazole discontinuation, and levothyroxine initiation resulting in gradual biochemical and symptomatic improvement. After achieving euthyroid state, levothyroxine was tapered however recurrent hyperthyroidism developed necessitating reinitiation of methimazole. Given the recurrent and unpredictable disease course, the patient underwent total thyroidectomy in 2024 and has remained stable on thyroid hormone replacement.



Discussion

This case highlights cyclic Graves’ disease with unusually rapid alternation between hyperthyroid and hypothyroid states occurring over days to weeks rather than the typical months to years. These fluctuations likely reflect dynamic shifts between thyroid-stimulating and thyroid-blocking antibodies. Frequent medication adjustments and the need for alternating antithyroid and thyroid replacement therapies further complicate management highlighting the challenges of achieving sustained biochemical control. Definitive treatment with thyroidectomy is often recommended.



Conclusion

Cyclic Graves’ disease should be considered when patents have marked thyroid hormone fluctuations. Early recognition and consideration of definitive therapy may improve long-term outcomes and quality of life.

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