Autoimmune hypothyroidism protects against breast cancer development in the elderly
Bibliographic record
Abstract
588 Background: An association between breast cancer and autoimmune hypothyroidism has been suggested. While a biological role for thyroid hormone in breast tumorigenesis has been demonstrated in vitro, epidemiological evidence is lacking. Methods: A retrospective, population-based cohort study was conducted to examine the risk of postmenopausal breast cancer (BRCA) in women with or without autoimmune hypothyroidism, identified on the basis of prescriptions for levothyroxine (LT4). Administrative health records were used to capture information on all women aged 66 and older living in Ontario, Canada at baseline (April 1, 1993 to March 31, 1996) and during a 10-year follow up. Propensity scores were used to create a matched cohort of LT4 and non-LT4 users. Cox proportional hazards modeling was used to evaluate the impact of LT4 use on the 5-year incidence of BRCA and benign breast disease, and on all-cause mortality rates among women diagnosed with breast cancer during follow-up. Results: LT4 users (N=89,093) and non-LT4 users (N=89,093) were well-matched with respect to baseline sociodemographics, estrogen use, comorbidity, and health care utilization, including the likelihood of receiving mammography or a breast biopsy. The 5-year incidence of BRCA was 0.86% in LT4 users compared to 0.97% in non-LT4 users (p=0.002). Adjustment for baseline characteristics did not alter these results (hazard ratio [HR] 0.86; 95% confidence interval [CI] 0.77–0.95; p= 0.004). Among women who developed BRCA, all cause mortality was significantly lower in LT4 users than in non-users (43.9% vs. 56.1%; adjusted HR 0.82; 95% CI 0.70–0.96; p= 0.01). The incidence of benign breast disease did not vary between groups. Conclusions: Elderly women with autoimmune hypothyroidism appeared to have a protective advantage in the incidence of BRCA and in mortality following a breast cancer diagnosis. These results suggest a biological role for thyroid hormone in the development of breast cancer, with a modulating effect of treated autoimmune hypothyroidism in promoting a less aggressive disease course. Further studies exploring the effect of thyroid hormone in breast cancer development are needed and may uncover novel therapeutic targets in the management of breast cancer in the future. No significant financial relationships to disclose.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".