Genetic and non-iodine-related factors in the aetiology of nodular goitre

Dietary Approach of Patients with Hormone-Related Cancer Based on the Glycemic Index and Glycemic Load Estimates

Hormone-related cancers, namely breast, endometrial, cervical, prostate, testicular, and thyroid, constitute a specific group of cancers dependent on hormone levels that play an essential role in cancer growth. In addition to the traditional risk factors, diet seems to be an important environmental factor that partially explains the steadily increased prevalence of this group of cancer. The composition of food, the dietary patterns, the endocrine-disrupting chemicals, and the way of food processing and preparation related to dietary advanced glycation end-product formation are all related to cancer. However, it remains unclear which specific dietary components mediate this relationship. Carbohydrates seem to be a risk factor for cancer in general and hormone-related cancers, in particular, with a difference between simple and complex carbohydrates. Glycemic index and glycemic load estimates reflect the effect of dietary carbohydrates on postprandial glucose concentrations. Several studies have investigated the relationship between the dietary glycemic index and glycemic load estimates with the natural course of cancer and, more specifically, hormone-related cancers. High glycemic index and glycemic load diets are associated with cancer development and worse prognosis, partially explained by the adverse effects on insulin metabolism, causing hyperinsulinemia and insulin resistance, and also by inflammation and oxidative stress induction. Herein, we review the existing data on the effect of diets focusing on the glycemic index and glycemic load estimates on hormone-related cancers.

Clinically diagnosed iron and iodine deficiencies and disorders in the entire population of US military service members from 1997 to 2015

OBJECTIVE

Iron and/or iodine deficiencies can have multiple serious adverse health outcomes, but examination of incidence rates of these deficiencies has rarely been conducted in any large population. This study examined incidence rates, temporal trends and demographic factors associated with medically diagnosed iron and iodine deficiencies/disorders in US military service members (SM).

DESIGN

The Defense Medical Epidemiological Database (DMED) was queried for medical visits of active duty SM to obtain specific International Classification of Diseases, Version 9, codes involving clinically diagnosed iron and iodine deficiencies/disorders.

SETTING

Analysis of existing database (DMED).

PARTICIPANTS

Entire population of US military SM from 1997 to 2015 (average n per year = 1 382 266, 15 % women).

RESULTS

Overall incidence rates for iron and iodine were 104 and 36 cases/100 000 person-years, respectively. Over the 19-year period, rates for iron disorders increased steadily (108 % for men, 177 % for women). Rates for iodine disorders also increased steadily for men (91 %), but, for women, there was an initial rise followed by a later decline. Overall, women's rates were 12 and 10 times higher than men's for iron and iodine, respectively. Compared with whites, blacks and those of other races had higher rates of deficiencies of both minerals. Incidence rates for iodine deficiency increased substantially with age.

CONCLUSIONS

The overall incidence of clinically diagnosed iron and iodine deficiency among SM was low, but increased over the 19 years examined, and certain demographic groups were at significantly greater risk. Given the unexpected increases in incidence of these mineral disorders, increased surveillance may be appropriate.Clinical Trial Registration No. ISRCTN58987177 (http//:www.isrctn.com/ISRCTN58987177).

Five-year follow-up and clinical outcome in euthyroid patients with thyroid nodules

BACKGROUND

Thyroid nodule diagnosis has become increasingly frequent. Defining optimum surveillance intervals for patients with unsuspicious thyroid nodules remains a challenge. This was a single centre cohort study in which patients diagnosed with unsuspicious thyroid nodules in whom no treatment was indicated were invited for re-evaluation 5 years after the diagnosis. The primary end point of the study was to estimate the change in nodule size with thyroid ultrasound (US) and the secondary end point was to assess the need for clinical management 5 years after the diagnosis.

PATIENTS AND METHODS

Baseline patient parameters and ultrasound characteristics of the nodules were retrospectively collected. At follow-up, thyroid ultrasound was performed.

RESULTS

A hundred and eighteen (107 women / 11 men, aged 56.8 ± 13.4 years) patients were included in the study having 203 nodules at baseline, with mean largest nodule diameter 10.5 ± 7.4 mm. After 5 years, 58 (28.6%) nodules significantly increased in size, 27 (13.3%) decreased, and for 104 (51.2%) of nodules, no change in size was noted. Fourteen (6.9%) nodules disappeared. Additional 26 new nodules (mean largest diameter 7.7 ± 5.0 mm) in 16 patients were identified at follow-up. Regarding the clinical outcome, no new thyroid cancers were found. For 107 (90.7%) patients no further management was indicated. Five (4.2%) patients were referred to thyroidectomy because of the growth of the nodules. Two (1.7%) patients were treated for hyperthyroidism. Four (3.4%) patients did not complete the study.

CONCLUSIONS

We report a single centre experience of the natural history of unsuspicious thyroid nodules. Our results showed that 71.4% of such nodules remained stable in size, decreased or even disappeared and that the vast majority of the patients remained clinically stable with no need for treatment 5 years after the diagnosis.

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.

Metformin reduces risk of benign nodular goiter in patients with type 2 diabetes mellitus

Background Whether metformin might affect the risk of benign nodular goiter in patients with type 2 diabetes mellitus has not been investigated. Methods Patients with new-onset type 2 diabetes mellitus during 1999-2005 were enrolled from Taiwan's National Health Insurance database. Analyses were conducted in a propensity score matched-pairs of 20,048 ever users and 20,048 never users of metformin. The patients were followed until December 31, 2011, for the incidence of benign nodular goiter. Hazard ratios were estimated by Cox regression incorporated with the inverse probability of treatment weighting using the propensity score. Results Among the never users and ever users of metformin, 392 and 221 cases were diagnosed of benign nodular goiter during follow-up, with incidence of 457.88 and 242.45 per 100,000 person-years, respectively. The overall hazard ratio for ever versus never users was 0.527 (95% confidence interval: 0.447-0.621). When cumulative duration of metformin therapy was divided into tertiles, the hazard ratios for the first (<25.3 months), second (25.3-57.3 months) and third (>57.3 months) tertiles were 0.815 (0.643-1.034), 0.648 (0.517-0.812) and 0.255 (0.187-0.348), respectively. Sensitivity analyses estimating the overall hazard ratios for patients enrolled in each specific year from 1999 to 2005 consistently showed a lower risk of benign nodular goiter among users of metformin. Conclusion Metformin use is associated with a lower risk of benign nodular goiter in patients with type 2 diabetes mellitus.

Insulin resistance is associated with larger thyroid volume in adults with type 1 diabetes independently from presence of thyroid autoimmunity

To investigate the effect of insulin resistance (IR) on thyroid function, thyroid autoimmunity (AIT) and thyroid volume in type 1 diabetes (T1DM). 100 consecutive patients with T1DM aged 29 (±6) years with diabetes duration 13 (±6) years were included. Exclusion criteria were: history of thyroid disease, current treatment with L-thyroxin or anti-thyroid drugs. Evaluation of thyroid stimulating hormone (TSH), free thyroid hormones and anti-thyroid antibodies was performed. Thyroid volume was measured by ultrasonography. IR was assessed using the estimated glucose disposal rate (eGDR) formula. In the study group 22% of subjects had insulin resistance defined as eGDR lower or equal to 7.5 mg/kg/min. The prevalence of thyroid autoimmunity (positivity for ATPO or ATg or TRAb) in the study group was 37%. There were no significant differences in the concentration of TSH, FT3, FT4, the prevalence of AIT and hypothyroidism between IR and insulin sensitive (IS) group. Mean (±SD) thyroid volume was 15.6 (±6.2) mL in patients with IR and 11.7 (±4.7) mL in IS subjects (p = .002). Thyroid volume correlated inversely with eGDR (r = -0.35, p < .001). In a multivariate linear regression model the association between thyroid volume and eGDR was independent of sex, age, duration of diabetes, daily insulin dose, BMI, cigarette smoking, TSH value and presence of thyroid autoimmunity (beta: -0.29, p = .012). Insulin resisance is associated with larger thyroid volume in patients with type 1 diabetes independently of sex, body mass index, TSH value and presence of autoimmune thyroid disease.

Hormonal and reproductive risk factors of papillary thyroid cancer: A population-based case-control study in France

The three times higher incidence of thyroid cancer in women compared to men points to a role of female sex hormones in its etiology. However the effects of these factors are poorly understood. We analyzed the association between thyroid cancer and hormonal and reproductive factors among women enrolled in CATHY, a population-based case-control study conducted in France. The study included 430 cases of papillary thyroid cancer and 505 controls frequency-matched on age and area of residence. The odds ratios for thyroid cancer increased with age at menarche (p trend 0.05). Postmenopausal women were at increased risk, as compared to premenopausal women, particularly if menopause followed an ovariectomy, and for women with age at menopause <55years. In addition, use of oral contraceptives and menopausal hormone therapy reduced the association with thyroid cancer by about one third, and breastfeeding by 27%. Overall, these findings provide evidence that the risk of thyroid cancer increases with later age at menarche and after menopause, and decreases with use of oral contraceptives and menopausal hormone therapy. These findings confirm an implication of hormonal factors in papillary thyroid cancer risk, whose mechanisms need to be elucidated.

Influence of iodide ingestion on nitrate metabolism and blood pressure following short-term dietary nitrate supplementation in healthy normotensive adults

Uptake of inorganic nitrate (NO₃^-) into the salivary circulation is a rate-limiting step for dietary NO₃^- metabolism in mammals. It has been suggested that salivary NO₃^- uptake occurs in competition with inorganic iodide (I^-). Therefore, this study tested the hypothesis that I^- supplementation would interfere with NO₃^- metabolism and blunt blood pressure reductions after dietary NO₃^- supplementation. Nine healthy adults (4 male, mean ± SD, age 20 ± 1 yr) reported to the laboratory for initial baseline assessment (control) and following six day supplementation periods with 140 mL·day^-1 NO₃^--rich beetroot juice (8.4 mmol NO₃^-·day^-1) and 198 mg potassium gluconate·day^-1 (nitrate), and 140 mL·day^-1 NO₃^--rich beetroot juice and 450 μg potassium iodide·day^-1 (nitrate + iodide) in a randomized, cross-over experiment. Salivary [I^-] was higher in the nitrate + iodide compared to the control and NIT trials (P < 0.05). Salivary and plasma [NO₃^-] and [NO₂^-] were higher in the nitrate and nitrate + iodide trials compared to the control trial (P < 0.05). Plasma [NO₃^-] was higher (474 ± 127 vs. 438 ± 117 μM) and the salivary-plasma [NO₃^-] ratio was lower (14 ± 6 vs. 20 ± 6 μM), indicative of a lower salivary NO₃^- uptake, in the nitrate + iodide trial compared to the nitrate trial (P < 0.05). Plasma and salivary [NO₂^-] were not different between the nitrate and nitrate + iodide trials (P > 0.05). Systolic blood pressure was lower than control (112 ± 13 mmHg) in the nitrate (106 ± 13 mmHg) and nitrate + iodide (106 ± 11 mmHg) trials (P < 0.05), with no differences between the nitrate and nitrate + iodide trials (P > 0.05). In conclusion, co-ingesting NO₃^- and I^- perturbed salivary NO₃^- uptake, but the increase in salivary and plasma [NO₂^-] and the lowering of blood pressure were similar compared to NO₃^- ingestion alone. Therefore, increased dietary I^- intake, which is recommended in several countries worldwide as an initiative to offset hypothyroidism, does not appear to compromise the blood pressure reduction afforded by increased dietary NO₃^- intake.

Human Exposures to Bisphenol A, Bisphenol F and Chlorinated Bisphenol A Derivatives and Thyroid Function

Although the increasing prevalence of thyroid nodular disease (TND) has been partially attributed to the more frequent usage of improved diagnostics, environmental factors, such as exposures to thyroid-disrupting chemicals may contribute to TND and altered thyroid function. We investigated the association between exposures to bisphenol A (BPA), its chlorinated derivatives (ClxBPA), and bisphenol F (BPF) with TND and thyroid measures in adult women. A case-control study in Cyprus and Romania (n = 212) was conducted, where cases were those with thyroid nodules (diameter >3mm), and controls without nodules. Serum TSH and free thyroxine and urinary levels of BPA, BPF and ClxBPA were measured using immunoassays and tandem mass spectrometry, respectively. The association between exposures to BPA compounds and TND, adjusting for age, BMI, thyroid hormones and urinary iodine was assessed using logistic regression. Linear regression was used to explore associations between urinary BPA, BPF and ClxBPA and serum thyroid hormones. With the exception of a chlorinated BPA compound (30%), the rest of bisphenols were quantified in 100% of urine samples. A positive and significant (p<0.05) association was observed between urinary BPA and serum TSH that remained after adjusting for urinary creatinine, age, BMI, study site and disease status; there was no significant association between BPF or ClxBPA with TSH. None of the BPA compounds were associated with higher odds of TND. Our study found associations of urinary BPA with TSH but not with BPF or ClxBPA. A larger study would be justified.

Benign thyroid nodules with RAS mutation grow faster

CONTEXT

The management of a benign thyroid nodule includes follow-up until its size requires a surgical or alternative treatment. To date, it is difficult or impossible to predict the size changes of a benign nodule in a given patient because no specific growth parameters exist. RAS mutations have been described in thyroid adenomas and hyperplastic benign nodules.

OBJECTIVE

The aim of this study was to establish whether the volume changes of benign nodules are associated with the presence of RAS mutation.

PATIENTS AND METHODS

Genomic DNA obtained by fine-needle aspiration of 78 thyroid nodules with benign cytology was analysed by pyrosequencing for the presence of NRAS(61) and KRAS(13) mutations. Ultrasonographic features were obtained. The volume of nodules at baseline and their changes after a mean follow-up of 25 months were evaluated according to the presence of RAS mutation.

RESULTS

A RAS mutation was found in 24 thyroid aspirates (30·8%, 8 NRAS(61) and 16 KRAS(13) ). RAS mutation was not associated with ultrasonographic features, but was significantly associated with a larger size at baseline (P = 0·017). After a 25-month mean follow-up, RAS mutation-positive nodules displayed faster growth (RAS mutation-positive vs RAS mutation-negative % annual growth 27·6% ±32·2% vs 1·0% ±17·0%, P < 0·001).

CONCLUSIONS

Benign thyroid nodules bearing RAS mutation grow more rapidly than those with wild-type RAS. Searching for RAS mutations in thyroid nodules with benign cytology might be useful to the clinician in choosing a more appropriate and timely surgical management.

Selenium and the thyroid

PURPOSE OF REVIEW

This article provides an update on the role of the essential trace element selenium and its interaction with the other trace elements iodine and iron that together contribute to adequate thyroid hormone status. Synthesis, secretion, metabolism and action of thyroid hormone in target tissues depend on a balanced nutritional availability or supplementation of these elements. Selenium status is altered in benign and malignant thyroid diseases and various selenium compounds have been used to prevent or treat widespread diseases such as goiter, autoimmune thyroid disease or thyroid cancer.

RECENT FINDINGS

Several studies, most with still too low numbers of cases, indicate that selenium administration in both autoimmune thyroiditis (Hashimoto thyroiditis) and mild Graves' disease improves clinical scores and well-being of patients and reduces thyroperoxidase antibody titers. However, published results are still conflicting depending on basal selenium status, dose, time and form of selenium used for intervention. Evidence for sex-specific selenium action, lack of beneficial effects in pregnancy and contribution of genetic polymorphisms (selenoprotein S) has been presented.

SUMMARY

Adequate nutritional supply of selenium that saturates expression of circulating selenoprotein P, together with optimal iodine and iron intake, is required for a healthy and functional thyroid during development, adolescence, adulthood and aging.