, working under the auspices of the Environmental
Protection Agency’s (EPA) Risk Assessment Forum, have examined the hypothesis that
TSH plays a significant role in thyroid carcinogenesis and that chemicals that produce
thyroid tumours in experimental animals would not show genotoxic potential in any
predictable way. Following detailed examination of three classes of compounds:
thionamides, aromatic amines and halogenated hydrocarbons, they conclude that ‘within
the limits of the present review, there does not seem to be a consistent relationship across
chemical classes that produce thyroid tumours and their ability to produce genotoxic
effects’. In man, no relationship between hypothyroidism and thyroid cancer has been
described and there is considerably less
support for a role of TSH in human thyroid carcinogenesis, compared with that for
rodents.