SAT-334 - Severe Hypokalemic Paralysis Revealing New-Onset Graves’ Disease

Introduction

Thyrotoxic periodic paralysis (TPP) is a rare but potentially life-threatening complication of hyperthyroidism that may present as acute paralysis with severe hypokalemia.

Methods

A retrospective review of the patient’s chart was performed, including history, laboratory data, ECG findings, treatment, and outcome. Relevant published literature was reviewed to support the interpretation of the case. We utilized software tools such as QuillBot, Zotero (for citation), and Perplexity to aid in project preparation.

Clinical case

We report a 26-year-old Asian male with recently diagnosed (within 3 weeks) hyperthyroidism who presented with sudden severe proximal muscle weakness in all 4 limbs with strength of 2/5. Pertinent labs included potassium of 1.5 mmol/L, Mg of 1.7 mg/dL, TSH of 0.007 mIU/L, free T4 of 3.8 ng/dL, and total T3 of 14.23 pg/mL. ECG showed QTc prolongation. The patient was placed on close cardiac monitoring, gradual potassium repletion, propranolol, and methimazole. Within 12 hours after treatment, he fully regained his muscle activity. The patient was later discharged and scheduled for an outpatient follow-up. Thyroid-stimulating immunoglobulin later returned positive at 16.5 IU/L, confirming Graves’ disease.

Discussion

This presentation is consistent with TPP as the initial manifestation of Graves’ disease. Previous reports describe TPP as a syndrome of thyrotoxicosis, hypokalemia, and acute painless weakness, often affecting men of Asian descent in their 20s and 30s [1]. The case underscores that even subtle hyperthyroid symptoms may be overlooked until paralysis occurs. Thyroid hormone and adrenergic stimulation increase Na-K ATPase activity in skeletal muscle, shifting potassium intracellularly and producing profound serum hypokalemia without total body potassium depletion [2]. QTc prolongation adds urgency because severe hypokalemia and thyrotoxicosis together increase the risk of arrhythmia and cardiac arrest. Early recognition is essential to prevent respiratory compromise, recurrent paralysis, and malignant cardiac events.

Conclusion

TPP should be considered in any young patient with acute paralysis and profound hypokalemia. In this case, new Graves’ disease was confirmed by positive TSI, and early treatment with slow potassium replacement, propranolol, and methimazole was critical to stabilization and outcome.

References

1. Frigo F, Kaun GR, Kaufmann C, et al. Silent thyrotoxicosis unveiled by sudden paralysis: a case report of thyrotoxic hypokalemic periodic paralysis. J Für Endokrinol Diabetol Stoffwechs. Published online March 11, 2026. doi:10.1007/s41969-026-00298-6
2. PoudelJaishi P, Neupane SK, Neupane PK. Case report: Hyperthyroid hypokalemic periodic paralysis. Ann Med Surg. 2022;78:103759. doi:10.1016/j.amsu.2022.103759

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