International Agency for Research on Cancer (IARC) - Summaries & Evaluations


VOL.: 7 (1974) (p. 53)

CAS No.: 56-04-2

5. Summary of Data Reported and Evaluation

5.1 Animal carcinogenicity data

Methylthiouracil (MTU) administered to mice, rats and hamsters by the oral route produced thyroid tumours in all 3 species. It was similarly effective in rats following s.c. implantation. Kidney tumours were induced in female rats following oral administration. It enhanced the tumourigenic response of local application of 9,10-dimethyl-1,2-benzanthracene, producing cervicovaginal tumours in ovariectomized female rats. In rats and hamsters, combined treatment with 131I and MTU, but not treatment with 131I alone, increased the incidence of malignant thyroid tumours. There exists an inverse relationship between iodine content of the diet and MTU thyroid tumourigenicity.

5.2 Human carcinogenicity data

No case reports or epidemiological studies were available to the Working Group.

Subsequent evaluation: Suppl. 7 (1987) (p. 66: Group 2B); Vol. 79 (2001)

For definition of Groups, see Preamble Evaluation.

Synonyms for Methylthiouracil

Last updated: 20 March 1998

    See Also:
       Toxicological Abbreviations
       Methylthiouracil  (IARC Summary & Evaluation, Volume 79, 2001)