The study is being criticized by the mainstream press, but the authors stand behind their findings and claim the result have been replicated many times (in animals studies).
http://www.newsweek.com/water-fluoridat ... ?piano_d=1
http://jech.bmj.com/content/early/2015/ ... 1.abstract
"...A large study that looked at data from nearly every general medical practice in England suggests that water fluoridation may increase the risk of developing hypothyroidism, or underactive thyroid. This condition, in which the thyroid gland doesn’t produce enough hormones, is associated with symptoms such as fatigue, obesity and depression. The study found that locations with fluoridated water supplies were more than 30 percent more likely to have high levels of hypothyroidism, compared to areas with low levels of the chemical in the water. Overall, there were 9 percent more cases of underactive thyroid in fluoridated places."
http://www.newsweek.com/water-fluoridat ... ?piano_d=1
http://jech.bmj.com/content/early/2015/ ... 1.abstract
"...A large study that looked at data from nearly every general medical practice in England suggests that water fluoridation may increase the risk of developing hypothyroidism, or underactive thyroid. This condition, in which the thyroid gland doesn’t produce enough hormones, is associated with symptoms such as fatigue, obesity and depression. The study found that locations with fluoridated water supplies were more than 30 percent more likely to have high levels of hypothyroidism, compared to areas with low levels of the chemical in the water. Overall, there were 9 percent more cases of underactive thyroid in fluoridated places."