Reproductive Factors and Risk of Thyroid Cancer in Women: An Analysis in the Nurses' Health Study II

Circulating endogenous sex steroids and risk of differentiated thyroid carcinoma in men and women

Thyroid cancer (TC) is substantially more common in women than in men, pointing to a possible role of sex steroid hormones. We investigated the association between circulating sex steroid hormones, sex hormone binding globulin (SHBG) and the risk of differentiated TC in men and women within the European Prospective Investigation into Cancer and nutrition (EPIC) cohort. During follow-up, we identified 333 first primary incident cases of differentiated TC (152 in pre/peri-menopausal women, 111 in post-menopausal women, and 70 in men) and 706 cancer-free controls. Women taking exogenous hormones at blood donation were excluded. Plasma concentrations of testosterone, androstenedione, dehydroepiandrosterone, estradiol, estrone and progesterone (in pre-menopausal women only) were performed using liquid chromatography/mass spectrometry method. SHBG concentrations were measured by immunoassay. Odds ratios (ORs) were estimated using conditional logistic regression models adjusted for possible confounders. No significant associations were observed in men and postmenopausal women, while a borderline significant increase in differentiated TC risk was observed with increasing testosterone (adjusted OR T3 vs T1: 1.68, 95% CI: 0.96-2.92, ptrend = .06) and androstenedione concentrations in pre/perimenopausal women (adjusted OR T3 vs T1: 1.78, 95% CI: 0.96-3.30, ptrend = .06, respectively). A borderline decrease in risk was observed for the highest progesterone/estradiol ratio (adjusted OR T3 vs T1: 0.54, 95% CI: 0.28-1.05, ptrend = .07). Overall, our results do not support a major role of circulating sex steroids in the etiology of differentiated TC in post-menopausal women and men but may suggest an involvement of altered sex steroid production in pre-menopausal women.

Rotating Night Shift Work, Sleep, and Thyroid Cancer Risk in the Nurses' Health Study 2

Night shift work has been associated with breast, prostate, and colorectal cancer, but evidence on other types of cancer is limited. We prospectively evaluated the association of rotating night shift work, sleep duration, and sleep difficulty with thyroid cancer risk in the Nurses' Health Study 2 (NHS2). We assessed rotating night shift work duration (years) at baseline and throughout follow-up (1989-2015) and sleep characteristics in 2001. Cox proportional hazard models, adjusted for potential confounders, were used to calculate hazard ratios (HR) and 95% confidence intervals (CI) for (a) shift work duration, (b) sleep duration, and (c) difficulty falling or staying asleep. We stratified the analyses of night shift work by sleep duration and sleep difficulty. Over 26 years of follow-up, 588 incident cases were identified among 114,534 women in the NHS2 cohort. We observed no association between night shift work and the risk of thyroid cancer. Difficulty falling or staying asleep was suggestively associated with a higher incidence of thyroid cancer when reported sometimes (HR 1.26, 95% CI 0.95, 1.66) and all or most of the time (HR 1.35, 95% CI 1.00, 1.81). Night shift workers (10+ years) with sleep difficulty all or most of the time (HR 1.47; 0.58-3.73) or with >7 h of sleep duration (HR 2.17; 95% CI, 1.21-3.92) had a higher risk of thyroid cancer. We found modest evidence for an increased risk of thyroid cancer in relation to sleep difficulty, which was more pronounced among night shift workers.

Metabolic Disease and Risk of Thyroid Disease: Evidence from the National Nurse Health Cohort in China

BACKGROUND

Previous studies have shown that metabolic diseases are risk factors for thyroid disease; most studies are cross-sectional design. We aimed to evaluate the causal relationship between thyroid and metabolic diseases in a cohort of Chinese nurses.

METHODS

We conducted an ambispective cohort study of the National Nurses' Health Study. Thyroid disease data based on ultrasonography from 2017 to 2021 were collected. We described thyroid disease incidence and the risk factors associated with a cluster of metabolic factors. We used the Mann‒Whitney U test, repeated-measures ANOVA and multivariable Cox proportional hazard regression to analyze the data.

RESULTS

A total of 1529 female nurses without thyroid disease were enrolled in 2017, of which, complete data were available for 1269 nurses. In 2018-2020, thyroid nodule incidence ranged from 32.8%-46.3%, thyroiditis incidence was 13.4%-14.3%, and goiter incidence was 4.1%-29.1%, thyroid adenoma and thyroid tumors incidence were 0.1%-0.5% and 1%-1.5%. We also found that NAFLAD was an independent risk factor for thyroid adenoma (p = .003). The age at diagnosis was an independent risk factor for goiter (p <. 001) and thyroid nodules (p < .001). Fasting blood glucose was an independent risk factor for thyroid tumors (p = .004). The age at diagnosis (p = .003), Body Mass Index (p = .006) and menopause (p = .031) were risk factors for thyroiditis.

CONCLUSION

Thyroid disease incidence among nurses is increasing. Age at diagnosis, BMI, fasting blood glucose, and nonalcoholic fatty liver disease are independent risk factors for different types of thyroid disease. This study provides evidence for future studies to further explore the pathogenesis and prevention of thyroid diseases.

Impact of modifiable reproductive factors on cancer incidence and mortality in Korea: a systematic review protocol

INTRODUCTION

Cancer is a leading cause of death worldwide. In Korea, it is also a major public health problem. Cancer burden may increase significantly due to ageing population and changes in lifestyle. The features of reproductive factors have changed, which include increased age at first childbirth and decreased breastfeeding duration. This study aims to systematically summarise the association between modifiable reproductive factors and cancer incidence and mortality to provide evidence for planning strategies aimed at reducing cancer incidence and mortality in women.

METHODS AND ANALYSIS

A literature search was performed using the EMBASE, MEDLINE, Cochrane Library and Korean databases such as the Korean Studies Information Service System, Research Information Sharing Service, KoreaMED, Korean Medical Database, National Assembly Library and Korea Institute from their inception to 24 August 2022. We will include cohort studies addressing the associations between at least one of the reproductive factors and the incidence and mortality of all or specific cancers among Korean women. Two reviewers will screen the references, extract the data, and assess the risk of bias independently and in duplicates. Discrepancies will be resolved through discussion or consultation with a third-party reviewer. We will use the Grading of Recommendations, Assessment, Development and Evaluation approach to evaluate the certainty of evidence. We will summarise the findings of the included systematic reviews through quantitative or narrative syntheses and present the summarised findings in tables.

ETHICS AND DISSEMINATION

Ethical approval is not required, since we will use only the published data. We will disseminate the study findings in peer-reviewed publications.

PROSPERO REGISTRATION NUMBER

CRD42022356085.

Hormonal Replacement Therapy and Risk of Thyroid Cancer in Women: A Meta-Epidemiological Analysis of Prospective Cohort Studies

Objectives

Many experimental studies have reported that female sex hormones involve thyroid cancer development because the incidence rate of thyroid cancer in women (TCW) is 3 times higher than in men. Three previous systematic reviews reporting no association between hormone replacement therapy (HRT) and TCW risk had the same search year of 2014. The aim was to reevaluate the association between HRT use and TCW risk using a meta-epidemiological study of prospective cohort studies.

Methods

The study preferentially used all studies selected by the existing systematic reviews and then secured an additional cohort from the list citing the studies. The selection criterion was defined as the prospective cohort study assessing the association between HRT and TCW risk by adjusted relative risk and its 95% confidence intervals (CI) from multivariate analysis. A random-effects model meta-analysis was applied to estimate summary relative risk (sRR) and its 95% CI. A publication bias was evaluated by Egger’s test; moreover, the statistical significance level was set at 5%.

Results

Nine cohort studies were finally selected. The random-effect model was applied because of heterogeneity (I² = 64.3%). The sRR and its 95% CI from a random-effects model meta-analysis had no statistical significance in the association between HRT and TCW risk (sRR = 1.11; 95% CI, 0.98–1.26). Additionally, Egger’s test revealed no statistical significance (P = 0.91).

Conclusions

HRT is not associated with TCW risk based on the random-effects model meta-analysis of prospective cohort studies published until now.

Thyroid cancer in women of reproductive age: Key issues for the clinical team

Women who are fertile experience a significant burden from thyroid cancer. In reality, delaying childbirth is the current trend in maternity. Women who have thyroid cancer may later want to get pregnant after it has been treated, which presents a multidisciplinary issue for their doctors. A variety of specialists are frequently involved in the treatment of thyroid cancer. This review aims to address the key elements of the strategy and places special emphasis on the significance of fertility in women with thyroid cancer diagnosis and remission. We will cover topics including the role of thyroid hormones in pregnancy and fertility.