Their article says:
Scientists who tested the blood of 4,000 US adults between 1996 and 2006 for the presence of the chemical perfluorooctanoic acid (PFOA) found the 25 per cent with the highest levels had twice the incidence of thyroid problems.
Animal studies have shown that the chemical can affect thyroid function, which is essential for maintaining heart rate, regulating body temperature and supporting other bodily functions. Researchers from the University of Exeter, who conducted the study … said they had demonstrated an association but had not proved causality. “Our results highlight the need for further research,” they said.
Updated: The study is now available online here. It concludes:
Higher concentrations of serum PFOA and PFOS are associated with current thyroid disease in the US general adult population. More work is needed to establish the mechanisms involved and to exclude confounding and pharmacokinetic explanations.