A thyroid hormone byproduct called rT3 might block the active thyroid hormone from working properly in your brain cells. This blockage could lower the hormone's effectiveness, which might play a role in causing certain mental health and brain development issues.

A substance called rT3 blocks your body's active thyroid hormones from working properly by taking their place on cellular receptors. This prevents your cells from getting the energy signals they need, which ultimately slows down your metabolism.

When your body is under long-term stress, trauma, or constant inflammation, it produces more of an enzyme that converts your main thyroid hormone into an inactive form. This leaves your cells starved of active thyroid hormone even though standard blood tests look normal, which can lead to brain fog, low mood, and cognitive problems.

This claim suggests that checking a specific thyroid hormone called rT3 in the blood could help doctors better understand mood and thinking problems. Adding this test to regular thyroid checks might lead to more accurate diagnoses and treatments tailored to how a patient's body processes hormones.

For people with mental health conditions, having higher levels of a specific thyroid hormone byproduct and a lower ratio of active thyroid hormones seems to go hand-in-hand with worse symptoms and less response to usual psychiatric medications. This suggests that how the body processes thyroid hormones might play a direct role in how severe the condition is and how well treatments work.

Reverse T3 is a naturally occurring thyroid hormone byproduct that makes up a significant portion of thyroid hormones in your blood. It's created when your body converts another hormone called T4, and its levels stay steady enough that doctors can easily measure them with current lab tests.