Reverse Triiodothyronine

Reverse T3 is an inactive thyroid hormone that can slow down your metabolism; testing it helps assess how well your thyroid is working, especially during stress or illness.

📋 About This Biomarker

Reverse T3 is a type of thyroid hormone that acts like a brake on your body's metabolism. While the active hormone T3 revs up your body's engine, reverse T3 slows it down. Your body makes reverse T3 from T4, another thyroid hormone, especially during times of stress or illness. It's like your body's way of conserving energy when it's under pressure. By measuring reverse T3 levels, we can see if your body is effectively using thyroid hormones or if it's producing more of this "slowing down" hormone. High levels might explain why you feel tired or sluggish even if other thyroid tests are normal.

🎯 Why We Test This

Testing reverse T3 gives a fuller picture of your thyroid health. If you're feeling symptoms of low thyroid function - like tiredness or weight gain - but standard tests are normal, measuring reverse T3 can reveal if your body isn't using thyroid hormones properly. It helps identify issues that might be missed otherwise, guiding better treatment choices.

⚠️ What Affects It

Several factors can influence reverse T3 levels. Stress - whether physical like illness or injury, or emotional stress - can cause levels to rise. A poor diet, especially very low-calorie diets, can increase reverse T3 as your body tries to conserve energy. Certain medications and chronic health conditions, such as liver or kidney problems, can also affect how your body processes thyroid hormones, impacting reverse T3 levels.

📈 How to Improve

If your reverse T3 levels are high or nearing high, reducing stress is crucial. This might include lifestyle changes like getting enough sleep, practising relaxation techniques, and eating a balanced diet. Addressing any underlying health issues and reviewing medications with your doctor can also help lower reverse T3 levels. If levels are low or close to low, usually no action is needed unless you have symptoms of an overactive thyroid; in that case, you should consult your healthcare provider.

📊 Understanding Your Results (pmol/L)

Low (< 141 pmol/L)
Low reverse T3 levels are rare and generally not worrisome. It might indicate that your body is converting more T4 into active T3. Unless you have symptoms like anxiety or a rapid heartbeat, which could suggest an overactive thyroid, low reverse T3 levels typically don't require action.
Optimal (141 - 370 pmol/L)
Normal reverse T3 levels indicate that your body is managing thyroid hormones well. Your metabolism is likely functioning properly, and your body is effectively converting T4 into the active T3 hormone needed for energy and various bodily functions. When reverse T3 levels are near the top of the normal range, it might be a warning sign that your body is starting to shift into energy-saving mode. This could be due to stress, a poor diet, or the beginning stages of an illness. It's a signal to pay attention to your health and possibly make lifestyle changes to prevent levels from rising further. If your reverse T3 levels are near the lower end of normal, it's usually not a concern. It suggests that less T4 is being converted into reverse T3, which might mean more is becoming active T3, supporting a healthy metabolism.
High (> 370 pmol/L)
If your reverse T3 levels are higher than normal, it suggests that your body is converting more T4 into reverse T3 instead of the active T3 hormone. This can slow down your metabolism, leading to symptoms like fatigue, weight gain, and feeling cold. It often happens when the body is under significant stress or during illness, and it means your thyroid hormones aren't being used effectively.
Also known as: rt3