title: Circulating thyroxine, thyroid-stimulating hormone, and hypothyroid status and the risk of prostate cancer.
abstract: BACKGROUND
  Thyroid hormones may influence risk of cancer through their role in cell differentiation, growth, and metabolism. One study of circulating thyroid hormones supports this hypothesis with respect to prostate cancer. We undertook a prospective analysis of thyroid hormones and prostate cancer risk in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study.
  
  
  METHODS
  Within the ATBC Study, a randomized controlled trial of α-tocopherol and β-carotene supplements and cancer incidence in male smokers, 402 prostate cancer cases were sampled. Controls were matched 2:1 to cases on age and date of blood collection. Odds ratios (OR) and 95% confidence intervals (CI) of prostate cancer were estimated for quintiles of serum total and free thyroxine (T4), thyroid-stimulating hormone (TSH), thyroid-binding globulin (TBG), and by categories of thyroid status.
  
  
  RESULTS
  Men with serum higher TSH had a decreased risk of prostate cancer compared to men with lower TSH (Q5 vs. Q1-4: OR = 0.70, 95% CI: 0.51-0.97, p = 0.03). When the T4 and TSH measurements were combined to define men as hypothyroid, euthyroid or hyperthyroid, hypothyroid men had a lower risk of prostate cancer compared to euthyroid men (OR = 0.48, 95% CI = 0.28-0.81, p = 0.006). We observed no association between hyperthyroid status and risk, although the number of hyperthyroid men with prostate cancer was small (n = 9).
  
  
  CONCLUSIONS
  In this prospective study of smokers, men with elevated TSH and those classified as being in a hypothyroid state were at decreased risk of prostate cancer. Future studies should examine the association in other populations, particularly non-smokers and other racial/ethnic groups.
authors.affiliation: Nutritional Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland, United States of America. mondulam@mail.nih.gov
authors.forename: Alison M
authors.initials: AM
authors.lastname: Mondul
authors.forename: Stephanie J
authors.initials: SJ
authors.lastname: Weinstein
authors.forename: Tracey
authors.initials: T
authors.lastname: Bosworth
authors.forename: Alan T
authors.initials: AT
authors.lastname: Remaley
authors.forename: Jarmo
authors.initials: J
authors.lastname: Virtamo
authors.forename: Demetrius
authors.initials: D
authors.lastname: Albanes
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D056726:Genetic Association Studies; D006801:Humans; D007037:Hypothyroidism; D008297:Male; D008875:Middle Aged; D011471:Prostatic Neoplasms / Q000097:blood / Q000235:genetics / Q000473:pathology; D012307:Risk Factors; D013960:Thyroid Function Tests; D013972:Thyrotropin / Q000097:blood / Q000235:genetics; D013974:Thyroxine / Q000097:blood / Q000235:genetics; D024502:alpha-Tocopherol / Q000097:blood; D019207:beta Carotene / Q000097:blood
chemical_list: D019207:beta Carotene; D013972:Thyrotropin; D024502:alpha-Tocopherol; D013974:Thyroxine