Critical Cases - Thyrotoxic Periodic Paralysis



  • 30 yo healthy male p/w generalized fatigue, b/l UE and LE weakness and pain for several hours
  • Denies strenuous activity, change in diet, falls, trauma, midline back pain, bowel and or bladder incontinence
  • Hospitalized 3 months prior for unexplained hypokalemia (K <2.0) that resolved with IV repletion



Vitals: BP 182/78 | Pulse 61 | Temp 97.7 °F (Oral) | Resp 22 | SpO2 100% 


  • Awake and alert, appears fatigued
  • Dry MM, cap refill greater than 3 seconds
  • 4/5 strength b/l UE
  • 3/5 strength b/l LE

    Sensation to light touch intact in bilateral upper and lower extremities

  • 2+ patellar reflexes bilaterally
  • Unable to ambulate due to weakness

Ddx for Generalized Weakness


  •  Hypokalemia/hyperkalemia vs rhabdomyolysis vs periodic paralysis vs spinal cord compression vs uillan Barre syndrome


Initial Diagnostics


  • Initial labs notable for K 1.9, Mg 1.5, and P 1.1

    Initial ECG (see below)







  • Electrolytes repleted as follows…
    • 40 mEq oral K, 20 mEq IV K
    •  2 gm Mg over 2 hours

      2 tablets of Neutra-Phos


Case Progression


  • Ultimately diagnosed with hyperthyroidism, likely secondary to Graves’ disease
    • TSH <0.01
    • Ultrasound thyroid
      • Enlarged heterogeneous thyroid with diffusely increased vascularity
      • Thyroid nodule of the isthmus
    • Started on Methimazole and Propranolol


  • Presenting symptoms and electrolyte abnormalities attributed to thyrotoxic periodic paralysis


Thyrotoxic Periodic Paralysis (TPP)


  • Potentially life-threatening
  • Defined as the triad of
    • Muscle paralysis
    • Acute hypokalemia
    • Hyperthyroidism
  • Less than half of TPP patients exhibit clinical signs of hyperthyroidism
  • Rapid recognition and termination are mandatory to avoid potentially fatal complications of severe hypokalemia
    • Cardiac arrhythmias

      Respiratory failure

  • Management complicated by the thin line between refractory hypokalemia and rebound hyperkalemia
  • KCl supplementation is essential but often not enough to control TPP
  • IV propranolol has been reported to reverse weakness and hypokalemia in patients unresponsive to KCl administration



Bilha S, Mitu O, Teodoriu L, Haba C, Preda C. Thyrotoxic Periodic Paralysis-A Misleading Challenge in the Emergency Department. Diagnostics (Basel). 2020;10(5):316. Published 2020 May 18. doi:10.3390/diagnostics10050316


Lin SH, Huang CL. Mechanism of thyrotoxic periodic paralysis. J Am Soc Nephrol. 2012;23(6):985-988. doi:10.1681/ASN.2012010046