Environmental pollutants are in the food we eat, the air we breathe and the water we drink and bathe in. In excess, they can have profound negative effects on the basic mechanisms of body chemistry and affect the synthesis and actions of hormones essential for maintaining our health. The thyroid, which is primarily responsible for regulating metabolism, is profoundly affected by both natural and environmental pollutants.
Iodine and Selenium: Essential Nutrients for Thyroid Function
Iodine and selenium are supplied in the food, water and nutrients we consume. Low levels in these sources can directly impact thyroid hormone synthesis and action. This may impact physical development, weight maintenance, heat production and the ability of tissues and glands to produce other hormones — resulting in the myriad of symptoms associated with low thyroid production and thyroid imbalance.
Surprisingly, iodine and selenium deficiencies persist in many parts of the world — including developed nations. Iodine deficiency began to rise when iodised salt was replaced with regular salt in most restaurants, and the iodine commonly used in baking breads was replaced with bromine. Dietary shifts away from iodine-rich foods and iodine-deplete vegan diets have also resulted in lower iodine consumption.
Our Thyroid & Iodine Test Kit measures TSH, Free T4, Free T3, TPO antibodies and urinary iodine in a single at-home collection — identifying both thyroid dysfunction and the iodine deficiency that may be driving it.
Environmental Antagonists That Exacerbate Thyroid Dysfunction
Mild deficiencies in iodine and selenium can be exacerbated when pollutants are present. Bromine, arsenic and mercury inhibit iodine incorporation into thyroid hormone and selenium incorporation into selenoproteins. Foods such as cruciferous vegetables and soy also contain goitrogens that can block iodine intake and synthesis of thyroid hormone.
The Five Key Elements to Test
Since the five elements — iodine, selenium, bromine, arsenic and mercury — are excreted mainly in urine, the degree of exposure to them can be determined by urine testing. Knowing your exposure to these elements will help provide insight into why you may not synthesise adequate amounts of thyroid hormones, or why your thyroid hormone levels in blood may appear normal but you still suffer from thyroid deficiency symptoms.
Our Thyroid, Heavy Metals & Essential Elements Test combines a full thyroid panel with ICP-MS analysis of toxic and essential elements — measuring bromine, arsenic, mercury, selenium and iodine alongside TSH, Free T4, Free T3 and TPO antibodies. It is the most comprehensive way to assess both thyroid function and the environmental element exposures that may be undermining it.
When Standard Thyroid Tests Are Not Enough
Standard thyroid blood tests measure TSH and sometimes Free T4 — but they do not reveal whether iodine or selenium deficiency, or toxic element exposure, is impairing thyroid hormone synthesis at the cellular level. This is why patients can have “normal” thyroid results yet still experience fatigue, weight gain, brain fog and other classic thyroid symptoms.
For a comprehensive thyroid assessment with specialist interpretation, our Thyroid Test Kit (with Specialist Doctor Report) measures TSH, Free T4, Free T3 and TPO antibodies from a simple at-home blood spot collection, with a full specialist doctor report included to guide next steps.
Originally ZRT Laboratory. Reproduced with permission. Last reviewed: May 2026.