Do thyroid hormones change the sensitivity of heart receptors in rats?

This does not mean thyroid hormones have no effect on the heart. It only means that, based on what we’ve seen so far, the receptors themselves don’t become more or less responsive to those chemicals. The heart may still react differently due to other changes—like more receptors being present—but the way each receptor reacts to a signal appears unchanged.

We don’t yet know if this applies to all types of heart receptors or all chemicals involved. The evidence we’ve reviewed focuses on a specific set of responses under elevated thyroid conditions, and we haven’t seen data on normal hormone levels or other species.

What we’ve found so far points toward unchanged receptor sensitivity in rats with high thyroid hormone, but we can’t say this is true for every situation or every type of heart receptor. More research would be needed to understand the full picture.

In everyday terms: if a rat’s thyroid is overactive, its heart still listens to signals the same way—it just might hear them more often because there are more receptors, not because each one is more sensitive.