Conclusion:
In many cases, hypokalemia can be multifactorial. When potassium
replacements exceed the calculated deficit values by wide margin and
with suboptimal correction of potassium, secondary causes should be
entertained.
Persistent, refractory hypokalemia associated with muscle weakness
should prompt suspicion for thyrotoxic periodic paralysis. In suspected
cases, appropriate testing should include the measurement of free T3
levels along with a free thyroxine and TSH so that T3 toxicosis is not
missed.
References:
- Lam L, Nair RJ, Tingle L. Thyrotoxic periodic paralysis. Proc (Bayl
Univ Med Cent). 2006;19(2):126-129. doi:10.1080/08998280.2006.11928143
- Kelley DE, Gharib H, Kennedy FP, Duda RJ Jr, McManis PG. Thyrotoxic
periodic paralysis. Report of 10 cases and review of electromyographic
findings. Arch Intern Med. 1989 Nov;149(11):2597-600. doi:
10.1001/archinte.149.11.2597. PMID: 2818118
- Rhee EP, Scott JA, Dighe AS. Case records of the Massachusetts General
Hospital. Case 4-2012. A 37-year-old man with muscle pain, weakness,
and weight loss. N Engl J Med. 2012;366(6):553-560.
doi:10.1056/NEJMcpc1110051
- Lin SH, Huang CL. Mechanism of thyrotoxic periodic paralysis. J Am Soc
Nephrol. 2012;23(6):985-988. doi:10.1681/ASN.2012010046
- Clausen T. Hormonal and pharmacological modification of plasma
potassium homeostasis. Fundam Clin Pharmacol. 2010 Oct;24(5):595-605.
doi: 10.1111/j.1472-8206.2010.00859.x. PMID: 20618871.
- Clifford PS, Hellsten Y. Vasodilatory mechanisms in contracting
skeletal muscle. J Appl Physiol (1985). 2004 Jul;97(1):393-403. doi:
10.1152/japplphysiol.00179.2004. PMID: 15220322.
- Abdi H, Amouzegar A, Azizi F. Antithyroid Drugs. Iran J Pharm Res.
2019;18(Suppl1):1-12. doi:10.22037/ijpr.2020.112892.14005
Table 1: Sequential laboratory data