Triiodothyronine (T3) levels in relation to mortality from breast cancer and all-causes: a population-based prospective cohort study.

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Abstract

OBJECTIVE: The potential association between thyroid hormones and breast cancer has been investigated in a large number of studies without conclusive results. This study investigated T3 levels in relation to breast cancer mortality in a population with no breast cancer patients at baseline. An additional aim was to study T3 levels in relation to mortality from other cancers and all-cause mortality. DESIGN AND METHODS: This was a population-based prospective cohort study including 2,185 women in whom T3 levels were measured as part of a preventive health project, i.e. before diagnosis in women who later developed breast cancer. Mean follow-up was 24.1 years and record-linkage to The Swedish Cause-of-Death registry identified 471 women who died; 26 out of breast cancer, and 182 from other cancers. Mortality was assessed using a Cox's analysis, yielding hazard ratios (HR), with 95% confidence intervals. Analyses of T3 as a continuous variable were repeated for pre- and peri/postmenopausal women separately. RESULTS: T3 levels were positively associated with the risk of breast cancer specific death in the age-adjusted analysis: HR for T3 as a continuous variable was 2.80 (1.26-6.25). However, the crude analysis did not reach statistical significance. Breast cancer mortality was even higher in postmenopausal women: 3.73 (1.69-8.22), but stratified analyses included few events. There were no statistically significant associations between T3 levels and deaths from other cancers, age-adjusted HR: 1.09 (0.72-1.65) or all-cause mortality (1.25:0.97-1.60). CONCLUSIONS: This study, the first of its kind on prospectively measured T3 levels, indicates that T3 levels are positively associated with breast cancer specific mortality, and that this is not related to a general effect on all-cause mortality.

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Subject classification (UKÄ) – MANDATORY

  • Endocrinology and Diabetes
Original languageEnglish
Pages (from-to)483-490
JournalEuropean Journal of Endocrinology
Volume168
Issue number4
Publication statusPublished - 2013
Publication categoryResearch
Peer-reviewedYes

Bibliographic note

The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Emergency medicine/Medicine/Surgery (013240200), Surgery Research Unit (013242220), Pathology (Malmö) (013031000)

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