title: Menstrual and reproductive history and use of exogenous sex hormones and risk of thyroid cancer among women: a meta-analysis of prospective studies.
abstract: OBJECTIVE
  Thyroid cancer has a higher incidence in women than in men, and it has been hypothesized that hormonal factors may explain such disparity. We performed a meta-analysis of observational prospective studies to investigate the association between menstrual and reproductive variables and exogenous hormone use and the risk of thyroid cancer among women.
  
  
  METHODS
  We calculated summary relative risks and 95% confidence intervals (95% CI) using random effect models.
  
  
  RESULTS
  Overall, 5,434 thyroid cancer cases from twenty-four papers were included. Increasing age at first pregnancy/birth (SRR 1.56, 95% CI 1.01-2.42) and hysterectomy (SRR 1.43, 95% CI 1.15-1.78) were associated with thyroid cancer risk. Women that were in menopause at enrolment had a reduced thyroid cancer risk (SRR 0.79, 95% CI 0.62-1.01). No other menstrual, reproductive, and hormonal variable was associated with thyroid cancer risk.
  
  
  CONCLUSIONS
  Menstrual and reproductive factors may play a role in the etiology of thyroid cancer, possibly through the mediation of estrogen receptors.
authors.affiliation: Unit of Molecular and Nutritional Epidemiology, Institute for Cancer Research and Prevention (ISPO), Via delle Oblate 2, 50139, Florence, Italy, saverio.caini@gmail.com.
authors.forename: Saverio
authors.initials: S
authors.lastname: Caini
authors.forename: Bianca
authors.initials: B
authors.lastname: Gibelli
authors.forename: Domenico
authors.initials: D
authors.lastname: Palli
authors.forename: Calogero
authors.initials: C
authors.lastname: Saieva
authors.forename: Massimilano
authors.initials: M
authors.lastname: Ruscica
authors.forename: Sara
authors.initials: S
authors.lastname: Gandini
mesh_terms: D005260:Female; D012739:Gonadal Steroid Hormones / Q000008:administration & dosage; D006801:Humans; D015994:Incidence; D008593:Menopause / Q000502:physiology*; D008598:Menstruation / Q000502:physiology*; D011247:Pregnancy; D012098:Reproduction / Q000502:physiology; D017584:Reproductive History; D012307:Risk Factors; D013964:Thyroid Neoplasms / Q000453:epidemiology*
chemical_list: D012739:Gonadal Steroid Hormones