Hormone Health Hub: Expert Insights on Testing, Balance & Better Living — Thyroid Function

Reverse T3 (rT3) is one of the most misunderstood markers in thyroid testing. Often called the “hibernation hormone,” it is frequently claimed — without scientific basis — to block thyroid receptors and slow metabolism. In Part 2 of this series, Margaret Groves of ZRT Laboratory examines what the peer-reviewed literature actually says about rT3, when elevated levels are clinically meaningful, and how to interpret the T3/rT3 ratio in the context of a comprehensive thyroid assessment.

Millions of people struggle with weight gain, fatigue and low mood despite being told their thyroid test results are “normal.” The problem is that a standard TSH test alone cannot identify the full range of factors that suppress thyroid function — from oestrogen dominance and elevated cortisol to iodine deficiency, selenium deficiency, heavy metal toxicity and xenoestrogen burden. This article explains what those hidden saboteurs are and how targeted testing can help identify them.