By Dr. Jacob Martin, MD
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 Guillain-Barre syndrome
Initial Diagnostics:
- Initial labs notable for K 1.9, Mg 1.5, and Phos 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
