Background: periodic paralysis related to hypokalemia is seldom reported in thyrotoxicosis, and it usually occurs in Asian males.

Patients and methods: Two Romanian (Caucasian) young patients presented with hypokalemic paralysis. TSH, FT4, TT3 was measured by immunochemiluminescence.

Case report 1. Patient O.R, aged 19, presented marked asthenia and lower limbs paralysis, following high carbohydrate meal. He declared 10 kg weight loss on hypocaloric diet and mild sweating. Biochemical data revealed moderate hypokalemia (K+=2.6 mmol/L) and thyrotoxicosis (TSH<0.03 mIU/L, FT4=30 pmol/L, TT3=315 ng/dL).

Case report 2. Patient T.A., aged 18, presented 2 episodes of weakness and flaccid paralysis, with hypokalemia, precipitated by effort, without any sign of thyrotoxicosis. Biochemical data revealed severe hypokalemia (K+=1.8 mmol/L) and thyrotoxicosis (TSH<0.03 mIU/L, FT4=24 pmol/L, TT3=190 ng/dL). Treatment with intravenous potassium, thereafter methimazole and propranolol were administered in both cases, with the maintenance of normal kalemia and thyrotoxicosis’ control.

Conclusion: these 2 cases of hypokalemic periodic paralysis occurring in young Caucasian teenagers with mild thyrotoxicosis underlined the importance of thyroid screening in patients with symptomatic hypokalemia, even in the absence of symptoms and signs of thyrotoxicosis.

Abbreviations: THPP=Thyrotoxic periodic paralysis, BMI=body mass index, TRAb=TSH receptor antibody, ECG=electrocardiogram.