The Claim
In adults receiving thyroid hormone replacement therapy, sustained TSH levels below 0.1 mIU/L are associated with a 6% increased risk of incident heart failure, and sustained free thyroxine levels above 1.9 ng/dL are associated with a 23% increased risk of incident heart failure.
What the research says
Supports is higher
Support is ahead, but a single strong opposing study can change this.
These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.
In adults taking thyroid hormone medication, consistently having too much hormone in the blood—measured by very low TSH or high free thyroxine—is linked to a higher chance of developing heart failure.
See the scientific wording
In adults on thyroid hormone replacement, sustained over-replacement defined as TSH below 0.1 mIU/L is associated with a 6% increased risk of incident heart failure, and elevated free thyroxine (FT4) above 1.9 ng/dL is associated with a 23% increased risk, indicating that excessive thyroid hormone dosing also contributes to cardiovascular risk.
What the research says
1 studyStudy: Association between Over- and Under-Replacement with Thyroid Hormone and Incident Heart Failure
This study found that adults taking too much thyroid hormone medicine have a slightly higher chance of developing heart failure, especially if their thyroid hormone levels are too high. So yes, taking too much can be bad for your heart.
Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting studies
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.