A number of previous research has suggested that there is an association between fluoride ingestion and the incidence of hypothyroidism. In a cross-sectional study the researchers found that higher levels of fluoride in drinking water are linked with the prevalence of hypothyroidism. The West Midlands (a wholly fluoridated area) were nearly twice as likely to report high hypothyroidism prevalence in comparison to Greater Manchester (non-fluoridated area).

The authors of the study said the findings of the study raise particular concerns about the validity of community fluoridation as a safe public health measure.

Source

S Peckham et al  2015 J Epidemiol Community Health doi:10.1136/jech-2014-204971. Are fluoride levels in drinking water associated with hypothyroidism prevalence in England? A large observational study of GP practice data and fluoride levels in drinking water