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

(Group 2B)

For definition of Groups, see Preamble Evaluation.

Supplement 7: (1987) (p. 329)

CAS No.: 51-52-5

A. Evidence for carcinogenicity to humans (inadequate)

In one survey of 331 hyperthyroid patients treated with antithyroid drugs, including propylthiouracil, and later with thyroidectomy, four thyroid cancers (an excess of unspecified proportion) were diagnosed more than one year after the beginning of drug therapy [ref: 1]. There has been one case report of acute myeloblastic leukaemia following propylthiouracil treatment [ref: 2].

B. Evidence for carcinogenicity to animals (sufficient)

Propylthiouracil produced thyroid tumours in mice, rats, hamsters and guinea-pigs and pituitary adenomas in mice after its oral administration [ref: 3]. When administered orally to rats with N-methyl-N-nitrosourea given intravenously [ref: 4] or N-nitrosobis(2-hydroxypropyl)amine intraperitoneally [ref: 5], it induced malignant thyroid tumours.

C. Other relevant data

No adequate data were available to the Working Group.

Overall evaluation

Propylthiouracil is possibly carcinogenic to humans (Group 2B).

For definition of the italicized terms, see Preamble Evaluation.

Subsequent evaluation: Vol. 79 (2001)

Also see previous evaluation: Vol. 7 (1974)


1. Dobyns, B.M., Sheline, G.E., Workman, J.B., Tompkins, E.A., McConahey, W.M. & Becker, D.V. (1974) Malignant and benign neoplasms of the thyroid in patients treated for hyperthyroidism: a report of the cooperative thyrotoxicosis therapy follow-up study. J. clin. Endocrinol. Metab., 38, 976-998

2. Aksoy, M., Erdem, S., Tezel, H. & Tezel, T. (1974) Acute myeloblastic leukaemia after propylthiouracil. Lancet, i, 928-929

3. IARC Monographs, 7, 67-76, 1974

4. Milmore, J.E., Chandrasekaran, V. & Weisburger, J.H. (1982) Effects of hypothyroidism on development of nitrosomethylurea-induced tumors of the mammary gland, thyroid gland, and other tissues. Proc. Soc. exp. Biol. Med., 169, 487-493

5. Kitahori, Y., Hiasa, Y., Konishi, N., Enoki, N., Shimoyama, T. & Miyashiro, A. (1984) Effect of propylthiouracil on the thyroid tumorigenesis induced by N-bis(2-hydroxypropyl)nitrosamine in rats. Carcinogenesis, 5, 657-660


Last updated: 3 March 1998

    See Also:
       Toxicological Abbreviations
       Propylthiouracil  (IARC Summary & Evaluation, Volume 7, 1974)
       Propylthiouracil  (IARC Summary & Evaluation, Volume 79, 2001)