Comment: While this ecological study is, as detailed in the appraisal, deeply flawed and certainly cannot be used to draw any causal conclusions, it raised a provocative, hypothesis-generating question. Further studies have substantiated that there are links between levothyroxine use and cancer. The proposed mechanism—oxidative stress—is biologically plausible. We know that thyroid hormones are powerful […]

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Comment: While this is an observational study and cannot prove causation, the findings are nonetheless concerning, especially as it’s not the only study showing an association of levothyroxine use and cancer. A nation-wide study identifying a 24% increase in the odds of breast cancer associated with levothyroxine use (AOR 1.24) warrants serious attention from the […]

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Comment: This is an important, large-scale population study, even with the weaknesses of the study design. An adjusted odds ratio of 1.50 for any cancer is a significant signal that cannot be easily dismissed, particularly given the strong associations noted for brain (AOR 1.90) and breast (AOR 1.24) cancers. While the authors rightly point out […]

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