In people with thyroid disease, the levels of iodine, selenium, and zinc in thyroid tissue are typically within the range seen in earlier studies, even though the general population may have slightly low levels of iodine and selenium.

In patients with mild deficiencies of iodine and selenium, the levels of these elements in thyroid tissue change in ways that relate to the amount of thyroid-stimulating hormone present, suggesting that nutrient levels and thyroid activity are linked in diseased tissue.

In the thyroid gland, iodine levels differ greatly from one follicle to another, while selenium and zinc levels remain relatively consistent across follicles, suggesting iodine is actively regulated in a variable way, whereas selenium and zinc are distributed more evenly.

In people with thyroid diseases, higher levels of TSH in the blood are linked to lower amounts of iodine, selenium, and zinc in the thyroid tissue, indicating that thyroid function may be related to the balance of these trace elements.

We don't have strong enough proof to say whether mild or moderate iodine deficiency really affects thyroid function, because the studies done so far aren't very reliable or consistent.

Most cases of hypothyroidism occur because the immune system attacks the thyroid gland, and the thyroid naturally holds more selenium than most other tissues in the body.