HPI

• 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

PE

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)

Management

• 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

References

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