Tobacco and the thyroid
The thyroid gland sits in the neck and is responsible for metabolic control. It produces thyroid hormone which is involved in many of the body's metabolic processes. Among women with hypothyroidism, (insufficient thyroid hormone), smoking is reported to be responsible for both decreasing secretion of thyroid hormone and blocking its action, thus exacerbating the symptoms of hypothyroidism 1.
In addition, smoking is associated with Graves' opthalmopathy, a severe form of hyperthyroidism with eye involvement. Case-control studies have reported that smoking is over seven times more frequent among those with eye involvement and that smokers had more severe eye involvement.