The thyroid gland may be small, but it plays a monumental role in maintaining your body’s health. Located in the neck and shaped like a butterfly, this endocrine powerhouse regulates everything from metabolism to mood through the hormones it produces. Yet, thyroid hormone imbalances often go unnoticed—despite affecting millions. According to the American Thyroid Association, more than 12% of the U.S. population will develop a thyroid condition during their lifetime, and up to 60% of those affected may not even know it. These disorders are frequently misdiagnosed or overlooked, often dismissed as symptoms of stress, ageing, or other common conditions....
Iodine is an essential trace element required for thyroid hormone production, yet many people are unknowingly deficient. While iodised salt and seafood are well-known sources, dairy products, eggs, and seaweed also contribute significantly to daily intake. Changing dietary habits — including reduced milk consumption and the replacement of iodine with bromine in bread production — are quietly lowering iodine intake across the population. This article explains where dietary iodine comes from, why the body needs it, how it is absorbed and excreted, and how at-home urine testing can confirm whether your intake is adequate.
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.
Thyroid symptoms can persist even when thyroxine (T4) levels appear normal — because thyroid function is profoundly affected by anything that disrupts the conversion of T4 to the active hormone T3 at the cellular level. In Part 1 of this two-part series, Margaret Groves of ZRT Laboratory explains the three deiodinase enzymes (D1, D2 and D3) that act as gatekeepers to intracellular thyroid hormone bioavailability, what affects circulating levels of T3 and reverse T3, and why selenium, iodine and inflammatory conditions all play a critical role.
Iodine is an essential component of thyroid hormones T3 and T4, and plays a broader role in antioxidant defence and breast health. Yet many people are unknowingly deficient. This guide covers the recommended daily allowances for different life stages, the best dietary sources of iodine — from kelp to cod — and when testing your iodine and thyroid levels may be warranted.
