Scientists found tiny amounts of mercury in cells of the thyroid gland, but they didn't check if people with this mercury had thyroid problems — so we can't say mercury causes thyroid disease.

We analyzed the available evidence and found that tiny amounts of mercury have been detected in thyroid gland cells [1]. However, none of the studies examined whether people with this mercury exposure developed thyroid cancer or hypothyroidism. Because there was no link made between the presence of mercury and any thyroid condition, we cannot say mercury is connected to these health outcomes. The evidence we’ve reviewed so far shows mercury can be present in thyroid tissue, but it does not show whether that presence matters for thyroid function or disease risk. There are no studies that contradict this finding, but there are also no studies that go further to test for health effects. Without data on thyroid function, hormone levels, or cancer rates in people with mercury in their thyroid cells, we can’t say whether this finding is meaningful or not. Our current analysis shows a gap: we know mercury is there, but we don’t know what, if anything, it does. For now, the presence of mercury in thyroid cells remains an observation without a known health consequence. If you’re concerned about mercury exposure, focusing on known sources like certain fish or dental fillings may be more practical than worrying about its presence in thyroid tissue — since we still don’t understand what that means for your health.