Symptomatic Junctional Bradycardia Due to Untreated Hypothyroidism After Beta-Blocker Discontinuation: A Case Report.

Hypothyroidism is known to cause bradycardia, but there are no direct comparisons of the level of thyroid-stimulating hormone (TSH) to heart rate (HR) to assist in therapeutic hormonal management. This case presents a patient who developed symptomatic junctional bradycardia and underwent serial TSH testing to attempt to improve her HR while minimizing systemic toxicity from levothyroxine. The patient had a history of paroxysmal atrial fibrillation on beta-blocker therapy and hypothyroidism and developed symptomatic junctional bradycardia following a lapse in her thyroid supplementation. Upon initiation of hormonal replacement therapy, serial TSH levels were assessed as she continued to have episodic bradycardia with severe hypertension. Given the lack of evidence correlating TSH levels to HR, this case report calls for further studies to be conducted to create reliable guidelines in therapeutic management to prevent bradycardia events while minimizing systemic levothyroxine toxicity.