Use of exogenous hormones hormones and risk of papillary thyroid cancer (Washington, United States)

TGF-β1 Disrupts redox balance in PCCL3 thyroid cell and is sexually dimorphic expressed in rat thyroid gland

Thyroid diseases are more prevalent in women, and this difference seems to be associated with the oxidative stress found in the thyroid of females. Thyroid NADPH Oxidase 4 (NOX4) was shown to respond to estrogen, which can also modulate TGF-β1, a potent stimulator of NOX4. This study aimed to investigate the effects of TGF-β1 on redox homeostasis parameters in the rat thyroid cell PCCL3 and the interrelationship between estrogen and TGF-β1. TGF-β1 treatment increased both intra- and extracellular ROS generation along with NOX4 expression and reduced GPX and catalase activities, extracellular H2O2 scavenging capacity, and reduced thiol content. TGF-β1 mRNA and protein expression are higher in female thyroid glands of rats in comparison to males. Moreover, 17β-estradiol treatment enhanced TGF-β1 mRNA in PCCL3 cells, decreased extracellular bioavailability but did not activate Smad pathway. Our data suggest that higher levels of TGF-β1 in females are potentially related to higher ROS availability which may be associated with the sex disparity in thyroid disorders.

Thyroid cancer incidence disparities among ethnic Asian American populations, 1990-2014

PURPOSE

Asian/Pacific Islanders (APIs) are at high risk of thyroid cancer, hence we examined thyroid cancer's incidence among disaggregated API subgroups in the United States (U.S.) to identify potential ethnic-specific disparities.

METHODS

Data from 1990 to 2014 in the Surveillance, Epidemiology, and End Results Program (SEER) were used to compare age-adjusted incidence rates (AAIRs) of thyroid cancer for seven API ethnic subgroups to non-Hispanic whites (NHWs) using incidence rate ratios (IRRs) and 95% confidence intervals (CIs). Sex, age, tumor histotype, and year of diagnosis were considered. Trends were evaluated using average annual percent change (AAPC) statistics.

RESULTS

The highest AAIRs (per 100,000 person-years) were among Filipinos (female AAIR=20.49, male AAIR=7.06) and the lowest among Japanese (female AAIR=8.36, male AAIR=3.20). However, Filipinos showed significantly lower incidence of medullary tumors when compared to NHWs (female IRR=0.60, 95% CI 0.40-0.87, male IRR=0.26, 95% CI 0.26-0.51). The largest increasing trends were among Asian Indian/Pakistanis for females (AAPC=5.19, 95% CI 3.81 to 6.58) and Koreans for males (AAPC=4.57, 95% CI 3.14 to 6.03).

CONCLUSIONS

There are clear differences in thyroid cancer incidence and trends when U.S. API ethnic subgroups are examined separately. Disaggregating APIs in research can provide critical information for understanding thyroid cancer risk.

Cigarette Smoking and Estrogen-Related Cancer

Cigarette smoking is a known cause of many cancers, yet epidemiologic studies have found protective associations with the risk of four "estrogen-related" malignancies: endometrial cancer, endometrioid and clear cell ovarian cancers, and thyroid cancer. This review considers epidemiologic and biological aspects of these associations, focusing particularly on estrogen signaling, and contrasts them with those for breast cancer, another estrogen-related malignancy. The observational findings regarding the inverse associations are consistent and remain after adjustment for possible confounding factors. In general, women who smoke do not have lower circulating estrogen levels than nonsmokers, eliminating one possible explanation for reduced risks of these malignancies. For endometrial and endometrioid ovarian cancer, the negative associations could plausibly be explained by interference with signaling through the estrogen receptor α. However, this is unlikely to explain the lower risks of thyroid and clear cell ovarian cancers. For thyroid cancer, an anti-inflammatory effect of nicotine and reduced TSH levels from smoking have been proposed explanations for the inverse association, but both lack convincing evidence. While the overall impact of cigarette smoking is overwhelmingly negative, protective associations such as those discussed here can provide potential clues to disease etiology, treatment, and prevention.

Papillary Thyroid Cancer-Promoting Activities of Combined Oral Contraceptive Components

Background:

Thyroid cancer is more common in women at reproductive age, suggesting the relationship between its high-incidence and therapeutic use of hormonal medications, such as oral contraceptives (OCPs). The aim of this study was to identify the effect of low-dose combined OCP (LD-COC) on proliferation, apoptosis, and migration of human papillary thyroid cancer (PTC) BCPAP cell line.

Materials and Methods:

BCPAP cells were cultured and treated with the combination of 90nM levonorgestrel (LNG) and 20nM ethinylestradiol (EE) for 48 hours. Afterward, using 3-(4, 5-dimethylthiazol-2-yl) -2, 5-diphenyltetrazolium bromide (MTT) assay, the proliferation of the cells was measured. Apoptosis was determined by using a Caspase-3 ELISA kit. Migratory properties of combined LNG and EE were studied through wound scratch assay. The expression levels of pro-apoptotic factor BAX, anti-apoptotic factor Bcl2, and proliferation marker Ki67 were analyzed by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and western blotting.

Results:

Upon treatment with the combination of LNG and EE, proliferation and migration of BCPAP cells were significantly enhanced. However, LNG and EE remarkably inhibited apoptosis of these cells. Furthermore, treating PTC cells with combined LNG and EE caused a marked increase in the expression of Bcl2 and Ki67 and a considerable decrease in BAX levels (P˂0.05).

Conclusion:

Our data linked the use of COCs and the progression and aggressiveness of PTC, suggesting the role of these hormonal compounds as promoting factors for PTC tumors. Despite these observations, further investigations will be required to fully establish the pathogenic impact of these medications on PTC.

Reproductive factors and thyroid cancer risk: Meta-analysis

BACKGROUND

Assessed pooled risk on reproductive factors and oral contraceptives (OC) on thyroid cancer (TC) using published studies (1996-2017).

METHODS

Summary odds ratio (OR) for case-control studies (n = 10) and risk ratio (RR) for cohort studies (n = 9) was done.

RESULTS

OR was 1.43 (95% CI: 1.16-1.77) for age at menarche >14 years, 1.49 (95% CI: 1.19-1.86) for parity >2, 1.38 (95% CI: 1.18-1.61) for miscarriage/abortion, and 2.05 (95% CI: 1.39-3.01) for artificial menopause. A protective effect (ORs: 0.85; 95% CI: 0.72-0.99) on TC was observed for prolonged use of OCs. RR was 1.17 (95% CI: 0.90-1.57) for age at menarche >14 years, 1.10 (95% CI: 0.94-1.27) for parity >2, 1.20 (95% CI: 1.03-1.40) for miscarriage/abortion, and 2.16 (95% CI: 1.41-3.31) for artificial menopause and protective effect (RR: 0.78; 95% CI: 0.65-0.92) for prolonged use of OCs.

CONCLUSIONS

This meta-analysis supports an association due to changes in female hormones during menstrual cycle and pregnancy with the risk of TC and explains female preponderance.

Menstrual and reproductive factors in the risk of thyroid cancer in Japanese women: the Japan Public Health Center-Based Prospective Study

The aim of this study was to evaluate the associations between menstrual and reproductive factors and thyroid cancer risk among Japanese women. A total 54 776 women aged 40-69 years completed a self-administered questionnaire, which included menstrual and reproductive history. During 1990-2012, 187 newly diagnosed cases of thyroid cancer were identified. Hazard ratios (HRs) and 95% confidence intervals (CIs) for menstrual and reproductive factors and incidence of thyroid cancer were estimated using Cox proportional hazards regression. Postmenopausal women who had natural menopause were at reduced risk of thyroid cancer than premenopausal women in the age-area-adjusted model (HR: 0.62 per 1 year increase, 95% CI: 0.39-0.99), but this association was slightly attenuated and no longer statistically significant in the multivariable-adjusted model. On analysis by menopausal status, an inverse association between age at menarche and risk of thyroid cancer was observed for premenopausal women (HR: 0.83 per 1 year increase, 95% CI: 0.70-0.98, P trend=0.03), but not for postmenopausal women. The risk of thyroid cancer increased with surgical menopause compared with natural menopause (HR: 2.34, 95% CI: 1.43-3.84). Although increasing age at menopause and duration of fertility were associated with an increased risk of thyroid cancer, this association was not observed among postmenopausal women. This study confirmed that early age at menarche for premenopausal women and surgical menopause and late age at natural menopause for postmenopausal women were associated with the development of thyroid cancer. Our results support the hypothesis that exposure to estrogens increases the risk of thyroid cancer.

Reproductive Factors but Not Hormonal Factors Associated with Thyroid Cancer Risk: A Systematic Review and Meta-Analysis

Many studies have investigated the association between hormonal and reproductive factors and thyroid cancer risk but provided contradictory and inconclusive findings. This review was aimed at precisely estimating this association by pooling all available epidemiological studies. 25 independent studies were retrieved after a comprehensive literature search in databases of PubMed and Embase. Overall, common hormonal factors including oral contraceptive and hormone replacement therapy did not alter the risk of thyroid cancer. Older age at menopause was associated with weakly increased risk of thyroid cancer in overall analysis (RR = 1.24, 95% CI 1.00–1.53, P = 0.049); however, longer duration of breast feeding was related to moderately reduced risk of thyroid cancer, suggested by pooled analysis in all cohort studies (RR = 0.7, 95% CI 0.51–0.95, P = 0.021). The pooled RR in hospital-based case-control studies implicated that parous women were more susceptible to thyroid cancer than nulliparous women (RR = 2.30, 95% CI 1.31–4.04, P = 0.004). The present meta-analysis suggests that older age at menopause and parity are risk factors for thyroid cancer, while longer duration of breast feeding plays a protective role against this cancer. Nevertheless, more relevant epidemiological studies are warranted to investigate roles of hormonal and reproductive factors in thyroid carcinogenesis.

Linear reduction in thyroid cancer risk by oral contraceptive use: a dose-response meta-analysis of prospective cohort studies

STUDY QUESTION

Is there an association between oral contraceptive (OC) use and thyroid cancer risk in females?

SUMMARY ANSWER

OC use is inversely associated with the risk of thyroid cancer in females.

WHAT IS KNOWN ALREADY

OC use may be relevant to the risk of thyroid cancer as suggested by some epidemiological studies. However, the findings are inconsistent regarding the effect direction and size.

STUDY DESIGN, SIZE, DURATION

This systematic review and meta-analysis included a total of 1906 patients from about 1.3 million individuals who had participated in 9 prospective cohort studies. The follow-up length ranged 7.5-15.9 years.

PARTICIPANTS/MATERIALS, SETTING, METHODS

PubMed (MEDLINE) was searched through to January 2015 for eligible studies. References of relevant review articles were also manually screened. Prospective cohort studies that evaluated the association between OC use and thyroid cancer risk were included. Study characteristics including patients' characteristics, length of the follow-up and risk estimates were extracted. The quality of the studies was also assessed.

MAIN RESULTS AND THE ROLE OF CHANCE

The included studies were of high methodological quality according to the Newcastle-Ottawa Quality Assessment Scale. After pooling risk estimates from all the studies, there was a significant inverse association between the longest versus shortest duration of OC use and the risk of thyroid cancer [relative risk (RR) = 0.84, 95% confidence interval (CI) 0.73-0.97], with no considerable heterogeneity (I(2) = 26.1%). There was no significant publication bias. The significant association persisted in the subgroup of high-quality studies (RR = 0.84, 95% CI 0.72-0.97). By dose-response analysis, there was a linear relationship (P = 0.0001) between the duration of OC use and thyroid cancer risk. The summary RR for an increment of 1 year of OC use was 0.96 (95% CI 0.94-0.98), with no significant heterogeneity.

LIMITATIONS, REASONS FOR CAUTION

Individual patient data were unavailable for a more accurate estimation.

WIDER IMPLICATIONS OF THE FINDINGS

These results indicate that OC use may decrease the risk of thyroid cancer in females. This may have implications for women's decisions regarding the use of OC.

STUDY FUNDING/COMPETING INTERESTS

No funding was involved for this study. No conflicts of interest are declared.

Menstrual and reproductive factors, exogenous hormone use, and risk of thyroid carcinoma in postmenopausal women

PURPOSE

To investigate the association of reproductive factors and hormone therapy, including type of hormone therapy, with risk of thyroid cancer in postmenopausal women.

METHODS

We assessed these associations with risk of incident thyroid cancer in a cohort of 145,007 postmenopausal women enrolled in the Women's Health Initiative. Over 12.7 years of follow-up, 296 cases of thyroid cancer were identified, including 243 with papillary thyroid cancer. Cox proportional hazards models were used to estimate hazard ratios and 95 % confidence intervals for exposures of interest.

RESULTS

In both age-adjusted and multivariable-adjusted analyses, menstrual and reproductive factors including age at menarche, age at menopause, age at first birth, age at last live birth, parity, duration of breastfeeding, miscarriages, stillbirths, hysterectomy, bilateral oophorectomy, and use of oral contraceptives were not associated with risk of all thyroid cancer or papillary thyroid cancer. In addition, ever use of menopausal hormone therapy, current or former use, duration of use, and type were not associated with risk.

CONCLUSION

We found little support for associations of reproductive or hormonal factors with risk of developing thyroid cancer. Importantly, our study showed no association of type of hormone therapy used with thyroid cancer risk.

The impact of age and gender on papillary thyroid cancer survival

CONTEXT

Thyroid cancer predominately affects women, carries a worse prognosis in older age, and may have higher mortality in men. Superimposed on these observations is the fact that most women have attained menopause by age 55 yr.

OBJECTIVE

The objective of the study was to determine whether men contribute disproportionately to papillary thyroid cancer (PTC) mortality or whether menopause affects PTC prognosis.

DESIGN

Gender-specific mortality was normalized using age-matched subjects from the U.S. population. Multivariate Cox proportional hazard regression models incorporating gender, age, and National Thyroid Cancer Treatment Cooperative Study Group stage were used to model disease-specific survival (DSS).

PARTICIPANTS AND SETTING

Patients were followed in a prospective registry.

MAIN OUTCOME MEASURE

The relationships between gender, age, and PTC outcomes were analyzed.

RESULTS

The unadjusted hazard ratio (HR) for DSS for women was 0.40 [confidence interval (CI) 0.24-0.65]. This female advantage diminished when DSS was adjusted for age at diagnosis and stage with a HR encompassing unity (HR 0.72, CI 0.44-1.19). Additional multivariate models of DSS considering gender, disease stage, and various age groupings showed that the DSS for women diagnosed at under 55 yr was improved over men (HR 0.33, CI 0.13-0.81). However, the HR for DSS increased to become similar to men for women diagnosed at 55-69 yr (HR 1.01, CI 0.42-2.37) and at 70 yr or greater (HR 1.17, CI 0.48-2.85).

CONCLUSIONS

Although the overall outcome of women with PTC is similar to men, subgroup analysis showed that this composite outcome is composed of two periods with different outcomes. The first period is a period with better outcomes for women than men when the diagnosis occurs at younger than 55 yr; the second is a period with similar outcomes for both women and men diagnosed at ages greater than 55 yr. These data raise the question of whether an older age cutoff would improve current staging systems. We hypothesize that older age modifies the effect of gender on outcomes due to menopause-associated hormonal alterations.

Factors connected with the female sex seem to play an important role in differentiated thyroid cancer

AIM

The aim of the study was to analyze whether female sex hormones and other factors connected with the female sex could increase the risk of differentiated thyroid cancer (DTC).

MATERIAL AND METHODS

Ninety-nine patients with a mean age±SD of 40.5±5.9 years with DTC and 51 healthy women with a mean age of 36.52±8.3 years were examined. Gynecological and obstetric histories were taken and serum estradiol and progesterone levels were analyzed in all women.

RESULTS

Patients with DTC had more frequent menstrual cycle disturbances, used hormone-containing medicines more frequently, were mulitiparous more frequently, had spontaneous miscarriages more frequently, and their duration of lactation was significantly shorter than in controls. The mean serum estradiol level±SD in women with DTC was significantly higher than in the controls, in the follicular phase 193.74±66.31 vs. 157.63±42.88 pmol/l and in the luteal phase 519±176.9 vs. 369±71.49 pmol/l. The mean serum progesterone level±SD was higher in the controls than in patients with DTC, in the follicular phase: 2.11±0.70 vs. 1.38±0.56 nmol/l and in the luteal phase 20.95±17.46 vs. 17.31±12.28 nmol/l.

CONCLUSIONS

The results of these studies imply that estrogens may at least modify the proliferation of thyroid cancer cells. The sex hormones probably intensify the actions of other carcinogens as well.

Factors connected with the female sex seem to play an important role in differentiated thyroid cancer

AIM

The aim of the study was to analyze whether female sex hormones and other factors connected with the female sex could increase the risk of differentiated thyroid cancer (DTC).

MATERIAL AND METHODS

Ninety-nine patients with a mean age ± SD of 40.5 ± 5.9 years with DTC and 51 healthy women with a mean age of 36.52 ± 8.3 years were examined. Gynecological and obstetric histories were taken and serum estradiol and progesterone levels were analyzed in all women.

RESULTS

Patients with DTC had more frequent menstrual cycle disturbances, used hormone-containing medicines more frequently, were mulitiparous more frequently, had spontaneous miscarriages more frequently, and their duration of lactation was significantly shorter than in controls. The mean serum estradiol level ± SD in women with DTC was significantly higher than that in the controls, in the follicular phase 193.74 ± 66.31 vs. 157.63 ± 42.88 pmol/L and in the luteal phase 519 ± 176.9 vs. 369 ± 71.49 pmol/L. The mean serum progesterone level ± SD was higher in the controls than in DTC patients in the follicular phase: 2.11 ± 0.70 vs. 1.38 ± 0.56 nmol/L; in the luteal phase: 20.95 ± 17.46 vs. 17.31 ± 12.28 nmol/L.

CONCLUSIONS

The results of these studies imply that estrogens may at least modify the proliferation of thyroid cancer cells. The sex hormones probably intensify the actions of other carcinogens as well.

Estradiol modulates TGF-β1 expression and its signaling pathway in thyroid stromal cells

The higher prevalence of thyroid disease in women suggests that estrogen (E2) might be involved in the pathophysiology of thyroid dysfunction. To approach the question of the effect of stromal cells in the modulation of thyroid epithelial cells activity, we established and characterized a homogeneous stromal cell population (TS7 cells) of rat thyroid gland. These fibroblastic cells synthesize the cytoskeleton proteins α-smooth muscle actin and vimentin, produce basement membrane components and express the cytokine transforming growth factor beta 1 (TGF-β1). Here, we hypothesized that the effects of E2 on follicular thyroid cells are mediated by TGF-β1 synthesis and secretion by stromal cells (paracrine action). Thus we investigated the effect of E2 on TGF-β1 synthesis and its signaling pathway in TS7 cells. In addition, we analyzed the role of TGF-β1 signaling pathway as mediator of TS7-PC CL3 thyroid epithelial cells interactions. We report that TS7 stromal cells expressed α and β estrogen receptors (ERα and ERβ). Further, both isoforms of TGF-β1 receptors, TGFRI and TGFRII, were also identified in TS7 cells, suggesting that these cells might be a target for this cytokine in vitro. Treatment of TS7 cells with E2 induced both synthesis and secretion of TGF-β1. This event was followed by phosphorylation of the transcription factor Smad2, a hallmark of TGF-β1 pathway activation. Co-culture of PC CL3 cells onto TS7 cells monolayers yielded round aggregates of PC CL3 cells surrounded by TS7 cells. TS7 cells induced a decrease in iodide uptake by PC CL3 cells, probably by a mechanism involving TGF-β1. Moreover, E2 affected synthesis and organization of the extracellular matrix (ECM) components, tenascin C and chondroitin sulfate, in these co-culture cells. Our results point to the TGF-β1/Smad-2 signaling pathway as a putative target of estrogen actions on thyroid stromal cells and contribute to understanding the interplay between stromal and follicular cells in thyroid physiology.

Gender differences in thyroid cancer: a critical review

It has long been known that the incidence of thyroid cancer in women is significantly higher than that in men. The objective of this article is to review gender differences in thyroid cancer, as well as epidemiological, clinical and experimental research on the role of sex hormones, their receptors and other molecular factors in this well-established thyroid cancer gender discrepancy. Although more common in women, thyroid cancer typically presents at a more advanced stage and with a worse disease prognosis in men. Clinical evidence on the impact of estrogen and other sex hormones on thyroid cancer has remained inconclusive, although numerous experimental studies have suggested that these hormones and their receptors may play a role in tumorigenesis and tumor progression. Studies of thyroid cancer cell lines suggest that an imbalance between the two estrogen receptor (ER) isoforms, α and β, may be responsible for the cell proliferation seen with estrogen treatment. Expression studies on thyroid tumors indicate that they express ER and possibly progesterone receptors and androgen receptors, but there is conflicting evidence as to whether or not there is a difference in receptor status between thyroid cancers, benign thyroid lesions and normal thyroid tissue. There have been few studies evaluating the ERα/ERβ profiles in thyroid tumors and normal thyroid tissue. Our understanding of the underlying basis for sex differences in thyroid cancer has improved over the last few decades, but the relationship between gender and thyroid cancer risk has remained elusive. Areas for future research include ERα/ERβ profiling of normal and neoplastic thyroid tissue, association between ER status and tumor dedifferentiation, and evaluation of the signaling pathways by which estrogen and other sex steroids exert their effects on thyroid cancer cells. Sex steroid receptors, and then downstream signaling pathways, represent promising future therapeutic targets for thyroid cancer treatment, and further study is required.

Risk factors for thyroid cancer: an epidemiological review focused on nutritional factors

OBJECTIVES

The present review summarizes epidemiological evidence on risk factors for thyroid cancer (TC), in particular, nutritional factors.

METHODS

Searches of articles on the issue were conducted using MEDLINE.

RESULTS

Exposure to ionizing radiation, particularly during childhood, is the best-established risk factor for TC. There is also a strong association with history of benign nodules/adenoma or goiter. Iodine deficiency may induce an increasing incidence of benign thyroid conditions, but very high iodine intake also affects thyroid function and, possibly, TC risk. Among dietary factors, fish-the major natural source of iodine in human diet-is not consistently related to TC risk. High intake of cruciferous vegetables shows a weak inverse association with TC. Among other food groups, vegetables other than cruciferous are the only food group showing a favorable effect on TC, with an approximate 20% reduction in risk for subjects with the highest consumption. No effect on TC risk of alcohol, coffee, or other food-groups/nutrients emerged. Height and weight at diagnosis show a moderate positive association with TC risk.

CONCLUSION

At present, the only recognized measures for reducing TC risk is to avoid ionizing radiation and iodine deficiency, particularly in childhood and young women, and to increase vegetable consumption.

Postmenopause is associated with recurrence of differentiated papillary thyroid carcinoma

Differentiated papillary thyroid carcinoma (D-PTC) is the most common malignancy arising in the thyroid gland. There are gender differences in the incidence of PTC being mainly observed in females. Low-risk groups consisted of men younger than 40-year-old and women younger than 50-year-old, whereas the high-risk group are older patients. We believe that age is not enough to explain the clinical course of this neoplasm and hypothesize that aggressive behavior of D-PTC may be correlated with hormonal status. Studies that support this idea showed that the follicular neoplastic cells had higher estrogen receptor-alpha in premenopausal (28.1+/-4.5) than in postmenopausal women (14.2+/-2.9). According to author's prior observations, there are evidences correlating recurrence of D-PTC with postmenopause in women. Postmenopause status is characterized by estrogen decrease and FSH increases both associated with EGFR activation. Previous observations identified EGFR over-expression in D-PTC of postmenopause when compared with premenopausal ladies.

CONCLUSIONS

Postmenopause is an adverse factor for tumor evolution in women with D-PTC and is associated with EGFR expression. It's introduction in thyroid tumor stratification could be a fine tuning in predicting papillary thyroid carcinoma behavior.

Hormone replacement therapy in cancer survivors

OBJECTIVE

Thousands of women are treated each year for cancer; many of these are already in menopause, while other younger patients will go into early menopause due to surgery, or chemotherapy, or the need for radiotherapy to the pelvic region. In most cases the oncologist and the gynaecologist would advise these women against the use of HRT. The purpose of this paper is to review biological and clinical evidences in favour and against HRT use in the different tumours and to propose an algorithm that can help choosing the treatment for the single woman.

METHODS

We performed a systematic literature review through April 2002 concerning: (1) biological basis of hormonal modulation of tumour growth; (2) epidemiological data on the impact of HRT on different cancers risk in healthy women; (3) safety of HRT use in cancer survivors; (4) alternatives to HRT.

RESULTS

With the exception of meningioma, breast and endometrial cancer, there is no biological evidence that HRT may increase recurrence risk. In women with previous breast and endometrial cancer HRT is potentially hazardous on a biological basis, even if published data do not show any worsening of prognosis.

CONCLUSIONS

Even if a cautious approach to hormonal-dependent neoplasias is fully comprehensible and the available alternative treatment should be taken into greater consideration, the reticence to prescribe HRT in women previously treated for other non hormone-related tumours has neither a biological nor a clinical basis. An algorithm based on present knowledge is proposed.

Combined effects of glutathione S-transferase polymorphisms and thyroid cancer risk

Since exposure to ionizing radiation, a risk factor for thyroid cancer, may produce genotoxins potentially eliminated by glutathione-S-transferases, we conducted a case control study to evaluate the role of the GSTM1- and GSTT1-null genotypes and GSTP1 polymorphisms in thyroid cancer. The frequency of GSTP1 Ile/Ile, GSTM1-, and GSTT1-null genotypes was increased in cancer patients when compared with control population. Considering the genotypes over-represented in thyroid cancer patients as potential risk genotypes, we carried out an odds ratio (OR) analysis considering the presence of none, one, two, or three risk genotypes. The results obtained showed that the presence of three potentially risk alleles (GSTM1 null, GSTT1 null, and GSTP1 Ile/Ile) lead to a significant OR increase for all the cases, irrespective of the type of tumor (OR=2.91), for papillary (OR=3.64) but not for follicular tumors. The presence of GSTP1 Ile/Ile leads to a significant later age of tumor onset when compared with GSTP1 Ile/Val and Val/Val (P<0.05), suggesting a possible association between GSTP1 Ile/Ile and the age of disease manifestation. These results suggest that combined GST polymorphisms lead to a moderate increased risk for thyroid cancer, especially for the papillary type, and GSTP1 polymorphisms might modulate the age of onset of the disease.

Family history of benign thyroid disease and cancer and risk of thyroid cancer

In a population-based study of 313 case-control pairs in Kuwait, we evaluated whether a family history of benign thyroid disease (BTD) and thyroid or other cancers was associated with an increased risk of thyroid cancer, the second most common neoplasm among women in this and several other Arab countries in the Gulf region. Family history of BTD was reported by 78 (24.9%) cases and 40 (12.8%) controls in 132 and 57 relatives, respectively. There was an approximately 2-fold increased risk of thyroid cancer in individuals who had a mother (Odds Ratio (OR)=2.3; 95% Confidence Intervals (95% CI): 1.1-5.1), sister(s) (OR=2.6; 95% CI: 1.3-5.3) or aunt(s) (OR=2.1; 95% CI: 0.9-5.3) with BTD; there was also a significant trend in increasing risk with an increasing number of affected female relatives (P<0.0001). Stratification by age at diagnosis of the case showed that individuals aged </= 35 years, who had an affected first- or second/third-degree relative(s), had an approximately 3-fold increased risk of the cancer. Family history of thyroid cancer was reported by 9 (2.9%) cases in 13 relatives (11 females, 2 males) and by 3 controls in 3 relatives (all females) (OR=3.0; 95% CI: 0.8-11.1). The OR for all hormone-related cancers combined was 1.5 (95% CI: 0.8-2.6). There was no clear association with family history of breast or any other common cancer. Our data suggest that a family history of BTD is associated with an increased risk of thyroid cancer, and point to the role of familial susceptibility to BTD and thyroid cancer in the Kuwaiti population.

Case-control study of female thyroid cancer--menstrual, reproductive and hormonal factors

A case-control study including 204 histologically verified female thyroid cancer patients and an equal number of hospital controls individually matched with cases by sex, age (+/- 2 years), place of residence and time of hospitalization was performed during the period 1996-2000. In the analysis of data, univariate and multivariate conditional logistic regression, methods were applied. According to multivariate analysis, out of hormonal, menstrual and reproductive characteristics, risk factors for thyroid cancer were spontaneous abortions (odds ratio: OR = 1.89, 95% confidence interval (CI) = 1.03-3.50), oral contraceptives use (OR = 2.34, 95% CI = 1.31-4.18) and thyroid enlargement during pregnancy (OR = 16.44, 95% CI = 3.81-70.80). However, none of these three factors remained independently related to thyroid cancer after adjustment for other factors, which were significantly associated with thyroid cancer in the present study (history of residence in endemic goitre area, history of goitre or thyroid nodule, history of other endocrine diseases, radioactive iodine therapy, occupational exposure to various chemicals, family history of thyroid gland diseases and malignant tumours as well as intake of cruciferous vegetables and other vegetables, and consumption of smoked meat and cheese).

Epidemiology and primary prevention of thyroid cancer

The purpose of this review is to provide an account of our present knowledge about the epidemiology of nonmedullary thyroid carcinoma, to discuss the effects of environment, lifestyle and radiation on the risk of developing thyroid cancer, and to discuss aspects on primary prevention of the disease. In areas not associated with nuclear fallout, the annual incidence of thyroid cancer ranges between 2.0-3.8 cases per 100,000 in women and 1.2-2.6 per 100,000 in men, women of childbearing age being at highest risk. Low figures are found in some European countries (Denmark, Holland, Slovakia) and high figures are found in Iceland and Hawaii. Differences in iodine intake may be one factor explaining the geographic variation, high iodine intake being associated with a slightly increased risk of developing thyroid cancer. In general, lifestyle factors have only a small effect on the risk of thyroid cancer, a possible protective effect of tobacco smoking has been recently reported. Because of the (small) increase in risk of thyroid cancer associated with iodination programs, these should be supervised, so that the population does not receive excess iodine. The thyroid gland is highly sensitive to radiation-induced oncogenesis. This is verified by numerous reports from survivors after Hiroshima and Nagasaki, the Nevada, Novaja Semlja and Marshal Island atmospheric tests, and the Chernobyl plant accident, as well as by investigations of earlier medical use of radiation for benign diseases in childhood. These reports are summarized in the review. There appears to be a dose-response relation for the risk of developing cancer after exposure to radioactive radioiodine. The thyroid gland of children is especially vulnerable to the carcinogenic action of ionizing radiation. Thus, the incidence of thyroid cancer in children in the Belarus area was less than 1 case per million per year before the Chernobyl accident, increasing to a peak exceeding 100 per million per year in certain areas after the accident. It is a social obligation of scientists to inform the public and politicians of these risks. All nuclear power plants should have a program in operation for stockpiling potassium iodide for distribution within 1-2 days after an accident.

Reporting participation in case-control studies

Although low participation in case-control studies may threaten their validity, it is difficult to evaluate the potential problem of nonresponse across studies because the level of participation among subjects is not reported in a consistent manner. This commentary presents a proposal for standard reporting of the process by which control subjects are recruited to a study and the outcomes of recruitment attempts. We encourage authors to provide a description of the sampling frame, the method of selecting units from the frame, and the number of units selected. For each unit selected, an outcome should be classified into four broad categories: ineligible sampling unit, unable to determine eligibility, respondent not eligible, and respondent screened and eligible. Details should be provided in each category; these details would differ according to the method used to contact potential respondents (by random-digit dialing, by telephone from a list, in person, or by mail). The proportion who participated can be reported as the investigator sees fit, as long as reporting of the components is complete. The sampling frame and outcomes should be reported separately for various parts of the study, such as controls from different sources or those who gave biological specimens. Standardized reporting will allow an evaluation of the success of various methods in recruiting potential participants, and will contribute important information for assessing the validity of individual studies.

Epidemiology of reproductive and hormonal factors in thyroid cancer: evidence from a case-control study in the Middle East

Thyroid cancer is the second most common neoplasm among women in Kuwait and several other countries in the Middle East. Most of these countries also have relatively high birth and total fertility rates. To examine potential relationships between reproductive and hormonal factors and thyroid cancer, we conducted a population-based case-control interview study among 238 women diagnosed with thyroid cancer and a similar number of individually matched controls in Kuwait. Among the demographic variables, women with 12+ years of education had a significantly reduced risk of thyroid cancer (OR = 0.4; 95% CI: 0.2-0.8; p-trend <0.05). The average age at diagnosis (+/-SD) of thyroid cancer was 34.7 +/- 11 years. Events such as age at menarche, pregnancy, menopausal status and age at menopause were not associated with thyroid cancer. There was an association with age at last pregnancy and parity. Women who had their last pregnancy at ages > or = 30 years were at a significantly increased risk (OR = 2.1; 95% CI: 1.2-3.8); there was also a significant trend in risk with increasing age at last pregnancy. There was a modest increase in risk among women who had borne > or = 5 children (OR = 1.5; 95% CI: 0.9-2.5). A joint analysis of these factors showed that childbearing during the latter half of reproductive life had a substantial effect on the incidence of thyroid cancer; for any given level of parity, there was about a 2-fold increased risk if the age at last pregnancy was > or = 30 years. A substantial recent-birth effect, in relation to subsequent diagnosis of thyroid cancer, was observed during the second and third year after a birth (OR = 2.0; 95% CI: 1.0-4.1). In contrast, spontaneous abortion seemed to have a protective effect. There was a significant decrease in risk among women who had a miscarriage as outcome of first pregnancy (OR = 0.1; 95% CI: 0.03-0.4) and those who had experienced > or = 3 miscarriages (OR = 0.3; 95% CI: 0.1-0.8; p-trend <0.05). Overall, any female hormone use was not associated with thyroid cancer risk. New association is suggested for a history of post-partum thyroiditis (OR = 10.2; 95% CI: 2.3-44.8). These data support the hypothesis that reproductive factors and patterns may influence, or contribute to, the risk of thyroid cancer among women.

Thyrocyte integration, and thyroid folliculogenesis and tissue regeneration: perspective for thyroid tissue engineering

The thyroid gland is composed of many ball-like structures called thyroid follicles, which are supported by the interfollicular extracellular matrix (ECM) and a capillary network. The component thyrocytes are highly integrated in their specific structural and functional polarization. In conventional monolayer and floating culture systems, thyrocytes cannot organize themselves into follicles with normal polarity. In contrast, in 3-D collagen gel culture, thyrocytes easily form stable follicles with physiological polarity. Integration of thyrocyte growth and differentiation results ultimately in thyroid folliculogenesis. This culture method and subacute thyroiditis are two promising models for addressing mechanisms of folliculogenesis, because thyroid-follicle formation actively occurs both in the culture system and at the regenerative phase of the disorder. The understanding of the mechanistic basis of folliculogenesis is prerequisite for generation of artificial thyroid tissue, which would enable a more physiological strategy to the treatment of hypothyroidism caused by various diseases and surgical processes than conventional hormone replacement therapy. We review here thyrocyte integration, and thyroid folliculogenesis and tissue regeneration. We also briefly discuss a perspective for thyroid tissue regeneration and engineering.

Risk of papillary thyroid cancer in women in relation to smoking and alcohol consumption

Both smoking and alcohol consumption may influence thyroid function, although the nature of these relations is not well understood. We examined the influence of tobacco and alcohol use on risk of papillary thyroid cancer in a population-based case-control study. Of 558 women with thyroid cancer diagnosed during 1988-1994 identified as eligible, 468 (83.9%) were interviewed; this analysis was restricted to women with papillary histology (N = 410). Controls (N = 574) were identified by random digit dialing, with a response proportion of 73.6%. We used logistic regression to calculate odds ratios (OR) and associated confidence intervals (CI) estimating the relative risk of papillary thyroid cancer associated with cigarette smoking and alcohol consumption. A history of ever having smoked more than 100 cigarettes was associated with a reduced risk of disease (OR = 0.7, 95% CI = 0.5-0.9). This reduction in risk was most evident in current smokers (OR = 0.5, 95% CI = 0.4-0.7). Women who reported that they had ever consumed 12 or more alcohol-containing drinks within a year were also at reduced risk (OR 0.7, 95% CI = 0.5-1.0). Similar to the association noted with smoking, the reduction in risk was primarily present among current alcohol consumers. The associations we observed, if not due to chance, may be related to actions of cigarette smoking and alcohol consumption that reduce thyroid cell proliferation through effects on thyroid stimulating hormone, estrogen, or other mechanisms.