Endocrine Abstracts

Introduction: Levothyroxine is the standard treatment for hypothyroidism- safe, inexpensive and effective. However, guidelines now suggest a trial of Liothyronine in some cases, to improve persistent symptoms. There is less safety data available for this. Here we report a case of sudden death in a patient using Liothyronine and present a thorough literature review on its safety profile.

Case Summary: A 42-year-old woman, previously fit and well, was found dead in her house, unexpectedly. She was reportedly using Liothyronine, bought off the internet, unprescribed. Post-mortem examination showed no cardiac abnormalities, but did show bilateral pulmonary oedema, focal hepatic necrosis without inflammation, and an atrophic thyroid gland. Serum toxicology was unremarkable. The medical examiner reported the cause of death as ‘Sudden Unexpected Death in the setting of (chronic) liothyronine use’.

Literature Review: To set the coroner’s conclusion in context, we assessed national statistics for mortality in Wales from 2013-2022, which showed that while deaths ‘due to unknown causes’ are rare (n = 681, 0.185% of all deaths), deaths attributed to thyroid disease (excluding cancer) or thyroid medications, are even rarer (n = 101, 0.029% of all deaths). Also, the number of adverse events (AEs) including deaths due to Liothyronine and Levothyroxine in reports published by MHRA showed 23 deaths associated with Levothyroxine with no reported deaths associated with Liothyronine. Disproportionality analysis of the FDA database also showed no signal for death associated with Liothyronine. Finally, a systematic literature review including cohort studies and case-reports also showed that most Liothyronine AEs are mild-moderate symptoms of thyroid excess, with occasional serious AEs occurring only on significantly excessive doses than recommended.

Conclusion: While this case report highlights the common misconception of Liothyronine being harmful, overall, the evidence in literature confirms that the safety profile of Liothyronine isn’t much different than any other drug, especially in a monitored environment.