In people with subclinical hypothyroidism, higher levels of anti-thyroid peroxidase antibodies are linked to more frequent levothyroxine prescription and more irregular appearance of the thyroid gland on ultrasound.

Among people with mild thyroid dysfunction, higher levels of certain autoimmune markers are linked to fewer thyroid nodules and less fluid-filled (cystic) nodules.

A woman with Hashimoto’s thyroiditis, who had been stable on thyroid hormone replacement for ten years, developed hyperthyroidism alongside a change in her autoimmune antibodies from those targeting the thyroid peroxidase to those targeting the thyroid-stimulating hormone receptor.

In some people with Hashimoto thyroiditis, antibody levels may drop to undetectable levels without surgery, and this change may occur alongside improvement in ongoing hypothyroid symptoms even after taking levothyroxine.

People with autoimmune thyroid disease tend to have lower levels of selenium in their blood, whether their thyroid is underactive or overactive. This suggests the low selenium levels are linked to the autoimmune condition itself, not to whether the thyroid is producing too much or too little hormone.

Among people with mild thyroid dysfunction, higher levels of certain autoimmune markers correlate with higher levels of ferritin, a protein that stores iron in the body.