Relationship of thyroid hormone T3 to breast cancer

[Rich66]

Introduction: The potential association between hypo- and hyperthyroid disorders and breast cancer has been investigated in a large number of studies during the last decades without conclusive results. This prospective cohort study investigated prediagnostic levels of thyrotropin (TSH) and triiodothyronine (T3) in relation to breast cancer incidence in pre- and postmenopausal women.

Methods: In the Malmö Preventive Project, 2696 women had T3 and/or TSH levels measured at baseline. During a mean follow up of 19.3 years, 173 incident breast cancer cases were retrieved using record linkage with The Swedish Cancer Registry. Quartile cut-points for T3 and TSH were based on the distribution among all women in the study cohort. A Cox’s proportional hazards analysis was used to estimate relative risks (RR), with a confidence interval (CI) of 95%. Trends over quartiles of T3 and TSH were calculated considering a P-value < 0.05 as statistically significant. All analyses were repeated for pre- and peri/postmenopausal women separately.

Results: Overall there was a statistically significant association between T3 and breast cancer risk,
the adjusted RR in the fourth quartile, as compared to the first, was 1.87 (1.12 to 3.14). In postmenopausal women the RRs for the second, third and fourth quartiles, as compared to the first, were 3.26 (0.96 to 11.1), 5.53 (1.65 to 18.6) and 6.87 (2.09 to 22.6), (P-trend: <0.001). There were no such associations in pre-menopausal women, and no statistically significant interaction between
T3 and menopausal status. Also, no statistically significant association was seen between serum TSH and breast cancer.

Conclusions: This is the first prospective study on T3 levels in relation to breast cancer risk. T3 levels in postmenopausal women were positively associated with the risk of breast cancer in a dose response manner.

[Hopeful]

I think those reading this article will recognize a lot of bc tumor characteristics that are familiar: http://www.ncbi.nlm.nih.gov/pmc/arti...8/?tool=pubmed

Hopeful

[Hopeful]

I recently had my annual blood work from my onc, and asked him to include two additional tests, one for thyroid antibodies, and one for C Reactive Protein. The thyroid antibodies test came back well within normal parameters, and the CRP test (an indication of overall inflammation in the body) came back very low. So, I am relatively certain that my elevated TSH is not the result of auto immune antibodies. My TSH was between 6 & 7 (the cut off for the parameter is 5 at the lab) in 2004, prior to my bc dx. The latest test is also between 6 & 7. I went back through my test results, and found, to my surprise, that twice the TSH came back normal, albeit at the high end of the reference range, and both times occurred during the first year after dx, when I was on both Herceptin and AI tx, and following rads. I have no idea what to make of this, but I thought it was noteworthy.

Hopeful