Q: "Paradoxical hypokalemia" is more common in? - Select one
A) Hereditary hypokalemic periodic paralysis
B) Thyrotoxic hypokalemic periodic paralysis
Answer: B
Many patients with thyrotoxic periodic paralysis may develop worsening, "paradoxical" hypokalemia after potassium repletion. This phenomenon may even occur in the nonperiodic phase whenever potassium is repleted. The underlying pathophysiologic mechanism is increased thyroxine concentration, which causes exaggerated potassium uptake.
Interestingly, the treatment is further potassium repletion. Usually, the drop is around 0.4 mEq/L, which can be life-threatening in view of already critical hypokalemia in these patients. Unfortunately, these patients are prone to develop hyperkalemia after repletion.
The differential diagnosis is based on urinary potassium excretion rates. Patients with hereditary hypokalemic periodic paralysis have a low urinary excretion of potassium, while patients with paradoxical hypokalemia have higher urinary potassium excretion rates, higher renin levels, and require higher volumes of saline resuscitation.
#electrolytes
# nephrology
#neurology
References:
1. Shiang JC, Cheng CJ, Tsai MK, et al. Therapeutic analysis in Chinese patients with thyrotoxic periodic paralysis over 6 years. Eur J Endocrinol 2009; 161:911.
2. Sung CC, Cheng CJ, Chiang WF, et al. Etiologic and therapeutic analysis in patients with hypokalemic nonperiodic paralysis. Am J Med 2015; 128:289.
3. Qing G, Zakaria WNA, Rom FZM, Nik WNFHW, Zulkeflee HA, Rahim SNA. Thyrotoxic Hypokalemic Periodic Paralysis: Pathophysiological Mechanisms. Endocrinol Metab (Seoul). 2025 Dec;40(6):821-829. doi: 10.3803/EnM.2025.2554. Epub 2025 Dec 11. PMID: 41376301; PMCID: PMC12765881.
4. Holm-Yildiz S, Krag T, Witting N, Pedersen BS, Dysgaard T, Sloth L, Pedersen J, Kjær R, Kannuberg L, Dahlqvist J, de Stricker Borch J, Solheim T, Fornander F, Eisum AS, Vissing J. Hypokalemic periodic paralysis: a 3-year follow-up study. J Neurol. 2023 Dec;270(12):6057-6063. doi: 10.1007/s00415-023-11964-z. Epub 2023 Sep 1. PMID: 37656291; PMCID: PMC10632268.