Liothyronine use in a 17 year observational population-based study - the tears study

Area of Science:

• Endocrinology
• Pharmacology

Background:

• Thyroid hormone replacement therapy is crucial for managing hypothyroidism.
• Liothyronine (T3) and l-thyroxine (T4) are commonly used, but their comparative safety profiles, particularly regarding adverse outcomes, require further investigation.
• Large-scale studies on liothyronine's adverse event profile are limited.

Purpose of the Study:

• To compare adverse outcomes in patients treated with liothyronine versus those treated solely with l-thyroxine.
• To assess risks of cardiovascular disease, atrial fibrillation, fractures, and specific medication use associated with liothyronine.

Main Methods:

• An observational study utilizing data from Tayside, Scotland (1997-2014).
• Compared patients who used liothyronine (n=400) against those who only used l-thyroxine (n=33,955).
• Followed patients for mortality, disease admissions (cardiovascular, atrial fibrillation, fractures, cancer, mental diseases), and incident medication use (bisphosphonates, statins, antidepressants, antipsychotics).

Main Results:

• No increased risk of cardiovascular disease, atrial fibrillation, or fractures was observed for liothyronine users compared to l-thyroxine users.
• No difference in bisphosphonate or statin prescriptions was found.
• A significant increase in antipsychotic medication prescriptions was associated with liothyronine use (HR 2.26).
• A non-significant trend towards increased breast cancer and antidepressant use was noted.

Conclusions:

• Long-term liothyronine use does not appear to increase the risk of atrial fibrillation, cardiovascular disease, or fractures.
• An elevated incidence of antipsychotic medication use was observed in patients taking liothyronine.
• Further research may be warranted to explore the association between liothyronine and mental health medication use.