title: Propylthiouracil-induced hypothyroidism reduces xenograft tumor growth in athymic nude mice.
abstract: BACKGROUND
  Thyroid hormones are endocrine modulators of several vital processes that are crucial to tumor growth and differentiation. Several anecdotal reports in the literature suggest that some histologic types of carcinoma may remain in a dormant state for prolonged periods of time in patients with hypothyroidism, with eventual progression of the disease once the decreased thyroid function is identified and corrected.
  
  
  METHODS
  Oral propylthiouracil (PTU) was used to induce hypothyroidism in athymic nude mice that were subsequently inoculated with lung adenocarcinoma and prostate adenocarcinoma cells. Mice were also treated with a combination of PTU and thyroxine, which resulted in hyperthyroid levels of T(4).
  
  
  RESULTS
  Subcutaneous lung and prostate xenografts grew significantly more slowly in hypothyroid mice treated with PTU than in euthyroid or hyperthyroid mice, regardless of treatment with PTU. Tumors grew well in groups of mice that were changed from a hypothyroid state to a euthyroid state by withdrawal of oral PTU. Administration of PTU 3 weeks after tumor inoculation also caused the tumor growth to slow significantly compared with tumors in mice that did not receive PTU. Mice that received PTU and thyroxine had tumors that grew as well as the tumors in euthyroid control animals.
  
  
  CONCLUSIONS
  Our study indicates that human lung and prostate tumors do not grow well in hypothyroid nude mice, and that rendering these animals euthyroid has a significant impact on the growth rate of these tumors. Furthermore, in vitro and in vivo data indicated that this was not a result of an interaction of the tumor cells with PTU, but rather a result of the hypothyroid state.
authors.affiliation: Department of Medicine, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, USA.
authors.forename: C
authors.initials: C
authors.lastname: Theodossiou
authors.forename: N
authors.initials: N
authors.lastname: Skrepnik
authors.forename: E G
authors.initials: EG
authors.lastname: Robert
authors.forename: C
authors.initials: C
authors.lastname: Prasad
authors.forename: T W
authors.initials: TW
authors.lastname: Axelrad
authors.forename: D V
authors.initials: DV
authors.lastname: Schapira
authors.forename: J D
authors.initials: JD
authors.lastname: Hunt
mesh_terms: D000818:Animals; D013956:Antithyroid Agents / Q000494:pharmacology*; D002455:Cell Division; D006801:Humans; D007037:Hypothyroidism / Q000139:chemically induced / Q000503:physiopathology*; D008297:Male; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental / Q000097:blood / Q000473:pathology / Q000503:physiopathology*; D011441:Propylthiouracil / Q000494:pharmacology*; D013974:Thyroxine / Q000097:blood / Q000187:drug effects / Q000494:pharmacology; D013997:Time Factors; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured
chemical_list: D013956:Antithyroid Agents; D011441:Propylthiouracil; D013974:Thyroxine