Known triggers for autoimmune thyroid disease include cigarette smoke, stress, low selenium levels, seasonal
and food allergies, sex steroids particularly estrogens, excess dietary
iodine,
and trauma.
"Adequate selenium nutrition supports efficient thyroid hormone synthesis and metabolism and protects the thyroid gland from damage by excessive iodide exposure."
Dietary wise, brazil nuts contain the most selenium. Depending on the soil, anywhere from 50 - 90 mcg of selenium per nut.