title: Hormonal and reproductive factors and risk of postmenopausal thyroid cancer in the NIH-AARP Diet and Health Study.
abstract: Worldwide, thyroid cancer incidence rates are higher among women than men. While this suggests a possible etiologic role of female sex hormones, clear associations between hormonal and reproductive factors and thyroid cancer have not been observed. However, few large prospective studies have been conducted.
  
  
  
  Hazard ratios (HRs) and 95% confidence intervals (CIs) for hormonal and reproductive factors and incident thyroid cancer were estimated using Cox regression methods in the prospective US NIH-AARP Diet and Health Study. Between 1995 and 2006, 312 first primary incident thyroid cancers were diagnosed among 187,865 postmenopausal women ages 50-71 at baseline.
  
  
  
  Thyroid cancer was not associated with ages at menarche or menopause, menopause type, or parity. Oral contraceptive use for ≥10 years (vs. never use) was inversely associated with thyroid cancer risk (HR, 0.48; 95%CI, 0.28-0.84; P(trend)=0.01). Women who reported current menopausal hormone therapy at baseline had an increased thyroid cancer risk vs. never users (HR 1.38; 95% CI: 1.07-1.79) but there was no trend with increasing duration of use. Women with benign breast disease (BBD) had a significantly higher thyroid cancer risk vs. women without BBD (HR, 1.47; 95% CI, 1.09-1.99).
  
  
  
  Our results do not support a strong role for female hormonal and reproductive factors including ages at menarche and menopause, type of menopause or parity, in thyroid cancer etiology among postmenopausal women. Compared with previous studies, no clear patterns emerge for exogenous hormone use but further analysis in large, prospective populations may be informative. The HR for BBD is consistent with the one previous prospective analysis that examined this association.
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, 6120 Executive Blvd, Bethesda, MD 20892, USA. schonfes@mail.nih.gov
authors.forename: S J
authors.initials: SJ
authors.lastname: Schonfeld
authors.forename: E
authors.initials: E
authors.lastname: Ron
authors.forename: C M
authors.initials: CM
authors.lastname: Kitahara
authors.forename: A
authors.initials: A
authors.lastname: Brenner
authors.forename: Y
authors.initials: Y
authors.lastname: Park
authors.forename: A J
authors.initials: AJ
authors.lastname: Sigurdson
authors.forename: A
authors.initials: A
authors.lastname: Schatzkin
authors.forename: A
authors.initials: A
authors.lastname: Berrington de González
mesh_terms: D000368:Aged; D003278:Contraceptives, Oral, Hormonal / Q000627:therapeutic use; D015914:Estrogen Replacement Therapy; D005260:Female; D006801:Humans; D008572:Menarche; D008593:Menopause; D008875:Middle Aged; D010298:Parity; D017698:Postmenopause; D016016:Proportional Hazards Models; D017584:Reproductive History; D012307:Risk Factors; D013964:Thyroid Neoplasms / Q000453:epidemiology*
chemical_list: D003278:Contraceptives, Oral, Hormonal