A 14-year-old African-American male with hyperthyroidism and intermittent asthma from Long Island, New York presented with acute onset of bilateral leg weakness. The patient reported experiencing bilateral leg soreness after swimming 2 days prior to presentation but denied particularly intense activity. The soreness progressed to generalized weakness and pain. Upon wakening to go to the bathroom in the early morning, the patient found himself unable to bear his own weight. The patient otherwise denied recent fevers, shortness of breath, cough, congestion, nausea, vomiting, diarrhea, rash, headaches, or visual disturbances. Recent diet was not ascertained, however the patient reported eating his usual dinner the night prior to the onset of symptoms.
With regards to his past medical history, he was diagnosed with reactive airway disease at 8 months of age. He was well controlled on inhaler therapy with budesonide and albuterol and he had recently required rescue albuterol after experiencing chest tightness while playing football. Three months prior to this presentation he was evaluated for the complaints of fatigue, tremors, palpitations, heat intolerance, difficulty focusing in school, and weight loss without any history of muscle weakness. His physical examination was remarkable for a nontender goiter and proptosis. Subsequent bloodwork revealed a thyroid-stimulating hormone (TSH) level less than 0.01 mIU/L (normal 0.52-5.05 mIU/L) and an elevated T4 level of 30.4 mcg/dL (normal 4.84-10.13 mcg/dL), consistent with the diagnosis of Graves' disease. After a pediatric endocrinology consultation, he was prescribed methimazole (5 mg every morning, 10 mg every evening) and 25 mg atenolol daily. He was also instructed to avoid physical activity until his thyroid hormones had declined. He reported good medication compliance until approximately 2 weeks prior to current presentation at which point he ran out of medication at home and failed to refill the prescriptions. Family history was only significant for a maternal grandmother with hyperthyroidism.
On presentation to the emergency department the patient's vital signs were notable for tachycardia (109 bpm) and an elevated blood pressure (154/87 mmHg). Physical examination was remarkable for bilateral lower and upper extremity weakness with lower extremity areflexia and upper extremity hyporeflexia. Initial laboratory tests revealed a potassium level of 2.0 mmol/L (normal 3.4-4.7 mmol/L) and a TSH level less than 0.005 mIU/L. Electrocardiogram demonstrated normal sinus rhythm, no ST elevation, and positive U waves. Initial concern for intracranial hemorrhage or other central nervous system abnormalities were ruled out following normal imaging of the brain, including computed tomography scan and magnetic resonance imaging. The patient was given 40 meq potassium oral replacement therapy, 1 L of normal saline mixed with 20 meq of potassium, and 1 g of magnesium before being transferred to our hospital.
On arrival to the pediatric intensive care unit, the patient appeared comfortable and was answering questions appropriately. His muscle weakness had dramatically improved, however he continued to remain tachycardic (117 bpm) and hypertensive (128/70 mmHg). Muscle power in the proximal right lower extremity was appreciated to be 4/5, while full muscle power was appreciated in all the other extremities. Deep tendon reflexes in bilateral lower and upper extremities were 1+ and 2+ respectively. Cranial nerves II-XII were grossly intact and the rest of the neurologic examination was otherwise unremarkable. A thyroid function panel was obtained and demonstrated a TSH level of less than 0.005 mIU/L, T3 level greater than 651 ng/dL (normal 110.02-184.88 ng/dL), T4 level of 16.8 mcg/dL, and a free T4 level greater than 7 ng/dL (normal 1.03-1.77 ng/dL). Repeat basic metabolic panel revealed an improved potassium level of 4.7 mmol/L and magnesium level of 1.8 mg/dL. The pediatric endocrinology team advised re-initiation of 20 mg methimazole two-times daily and 20 mg propranolol three-times daily. His clinical status rapidly improved and he was discharged home on the second day of admission.
Upon follow-up the patient reported good medication compliance with no further episodes of weakness or worsening of pulmonary symptoms. Because he was asymptomatic, the propranolol was discontinued after 1 month and methimazole dosing was decreased to 10 mg daily after 3 months. Six months after discharge the patient remained clinically euthyroid. His thyroid hormonal profile revealed normalization of T4 (7.6 mcg/dL) however, he continued to have a low TSH (0.02 mIU/L) and an elevated thyroid stimulating immunoglobulin (400%; normal < 140%). He was instructed to continue methimazole 10 mg daily and to obtain repeat thyroid function tests prior to the next appointment in 3 months.