Thyrotoxic Periodic Paralysis : A Treatable Presentation of Weakness
Nor Hanan HAMZAH (1,3), Wan Norlina WAN AZMAN (1,3), Hanim Afzan IBRAHIM (1,2), Julia OMAR (1,3), Aniza MOHAMMAD JELANI (1,3), Nur Karyatee KASSIM (1,2*).

1) Department of Chemical Pathology, Hospital Universiti Sains Malaysia, USM Health Campus, 16150 Kubang Kerian, Kelantan, Malaysia.

2) Basic Sciences and Oral biology Unit, School of Dental Sciences, USM Health Campus, 16150 Kubang Kerian, Kelantan, Malaysia.

3) School of Medical Sciences, Universiti Sains Malaysia, USM Health Campus, 16150 Kubang Kerian, Kelantan, Malaysia.

Abstract

Introduction : Thyrotoxic periodic paralysis (TPP) is a rare complication of hyperthyroidism characterized by episodes of muscle weakness and hypokalemia. TPP is typically present in adolescent Asian male population. An assessment of renal potassium excretion, acid base status and thyroid function at presentation are very helpful in diagnosing TPP. During acute therapy, doses of Potassium Chloride (KCL) should be minimal to prevent rebound hyperkalemia, and non-selective --blocker may be alternative choice.

Method: A 29 years old gentleman with no known medical illness presented with progressive whole body weakness for 2 days. During initial presentation, he was still able to ambulate however, on the day of admission, he was unable to move ambulate. The weakness is symmetrical, proximal and started at lower limb. There was no respiratory distress, no numbness, no loose stool, no vomiting, no headache or dizziness, and no chest pain. He had on and off history of palpitation and tremor of both hands. But no history of excessive sweating, irritability, heat intolerance or weight loss. He also gives history of similar episode 2 months before current attack.

On examination, neck examination revealed diffuse thyroid enlargement. There was no ophthalmopathy. Respiratory and cardiovascular systems show no significant findings.
Power was normal in both upper limbs but reduced in both sides of lower limbs. On the right side the power was 3/5 and on the left side was 2/5. Tone was normal in both upper and lower limbs. Reflexes were normal and both plantar responses were normal bilaterally. His sensation was intact. Cranial nerves examinations were normal.

Results: Electrocardiography shows prolong QT complexes. His potassium level was 1.8mmol/L. Normal acid-base status together with urine spot potassium of <15mmol/L indicates that hypokalaemia is not due to renal potassium wasting. 2g KCL correction was done and the potassium rises to 1.9mmol/L. His thyroid function test showed biochemically hyperthyroid.

Conclusion: In summary, the goal of therapy in TPP is to normalize thyroid function and avoid the precipitating factors for acute attack.

Keywords: Thyrotoxic periodic paralysis, Hypokalemia, Potassium.

Topic: Biomedical Sciences