PSAT356 Propranolol Improves Bulbar Dysfunction Seen in Hyperthyroidism
Authors: Weinstein Robert , Albashaireh Arwa , Shah Aashka , Syed Sabah , Naqvi Syeda 
Published: November 2022

Abstract

Background
Many symptoms of hyperthyroidism are mediated by the augmented activity of the adrenergic central nervous system. Rarely, symptoms of bulbar dysfunction are seen with thyrotoxicosis such as dysphagia and dysarthria. Beta blockers can abort or reduce these symptoms before anti-thyroid drugs are used.

Case
A 59-year-old woman with hypertension and gout, presented to the emergency department with poor oral intake and difficulties swallowing. Symptoms initially started as hoarseness of voice for 3 weeks then progressed to Globus sensation, difficulties swallowing and aspiration of solids and liquids. She also reported generalized muscle weakness, palpitations, increased sweating, tremors and 20 pounds weight loss in the preceding 2 months.
Physical exam showed an ill-appearing, catechetic woman. Luedde exophthalmometry showed an absence of proptosis measuring 15 mm bilaterally without lid lag or stare and extraocular muscles were intact. The skin was silky without edema. The strength in the lower extremities was decreased and she was unable to squat or raise from a seated position.
Labs showed creatinine of 2.7 mg/dL (0.4–1 mg/dL), BUN 49 (6–20 mg/dL), potassium of 3.1 (3.5–5.1 mmol/L), TSH &lt; 0.02 (0.34–5.60 uIU/mL), FT4: 3.72.
CT of the neck was obtained and multiple sub-centimetric hypodense thyroid nodules with calcifications were noted in the left thyroid lobe.
Intravenous potassium chloride was given without improvement of dysphagia. 10 milligrams (mg) of propranolol were ordered to be given every 8 hours. After the first dose and over the next 24 hours she reported rapid improvement in dysphagia and muscle weakness.
She was discharged on 15 mg of methimazole twice daily and propranolol 10 mg thrice daily.
TSI and TRAB were elevated at 1.03 (normal &lt; 0.54 IU/L) and 2.20 (normal&lt;1.75 IU/L) respectively and the diagnosis of Graves’ disease was made.
At her 3 weeks follow up, TSH was &lt;0.02 (0.34–5.60 uIU/mL) with normal FT4. She reported complete resolution of dysphagia and improvement in lower extremities weakness.

Discussion
Hyperthyroidism may exert powerful effects on the neuro-muscular system. The pathogenesis of myopathy in hyperthyroidism is not fully understood. In hyperthyroid periodic paralysis, hypokalemia is present, and paresis is corrected with potassium supplementation. Our patient's symptoms did not improve with potassium supplement but dramatically improved after propranolol use and before the thyroid function was normalized. This implies a role of adrenergic overactivity in myopathy of hyperthyroidism. A study1 was conducted to quantify muscular weakness in hyperthyroidism and assess the response to therapy concluded that propranolol improves muscular weakness.

Conclusion
Prior to normalization of thyroid function, the use of beta blockers can alleviate symptoms of bulbar dysfunction.
(1)Olson BR, Klein I, Benner R, Burdett R, Trzepacz P, Levey GS. Hyperthyroid myopathy and the response to treatment. Thyroid. 1991;1(2): 137-41. doi: 10.1089/thy.1991.1.137. PMID: 1688015.
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