Nutrition and thyroid disease

PURPOSE OF REVIEW

The aim of this review was to determine, based on the most recent findings, the involvement of trace elements and vitamins critical for thyroid function and combating thyroid disease.

RECENT FINDINGS

Nutritional guidance is pivotal to reducing the risk of thyroid disease and to managing it when it arises, this meaning the prescription of diets rich in such micronutrients as iodine, selenium, iron, zinc, and vitamins B12, D3, and A. Most of the above micronutrients are good antioxidants, building up an anti-inflammatory profile, reducing thyroid autoantibodies and body fat, and improving thyroid function. Diets are increasingly being prescribed, especially for those suffering from Hashimoto's thyroiditis. Notable among prescribed diets is the Mediterranean diet. Rich in critical elements, it benefits patients at the immune endocrine and biomolecular levels.

SUMMARY

Importantly, it is likely that widespread adherence to the Mediterranean diet, together with a reduction of meat consumption and potential elimination of gluten and lactose may improve inflammation and have an impact on public health while possibly diminishing thyroiditis symptoms. It is hoped that this review can direct policymakers towards undertaking cost-effective interventions to minimize deficiency of essential minerals and vitamins and thus protect both general and thyroid health.

Metabolic, Oxidative and Psychological Stress as Mediators of the Effect of COVID-19 on Male Infertility: A Literature Review

Over 300 million patients with coronavirus disease 2019 (COVID-19) have been reported worldwide since the outbreak of the pandemic in Wuhan, Hubei Province, China. COVID-19 is induced by the acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The effect of SARS-CoV-2 infection on the male reproductive system is unclear. The aim of this review is to assess the effect of SARS-CoV-2 infection on male fertility and the impact of possible mediators, such as metabolic, oxidative and psychological stress. SARS-CoV-2 infection aggravates metabolic stress and directly or indirectly affects male fertility by reducing seminal health. In addition, SARS-CoV-2 infection leads to excessive production of reactive oxygen species (ROS) and increased psychological distress. These data suggest that SARS-CoV-2 infection reduces male fertility, possibly by means of metabolic, oxidative and psychological stress. Therefore, among other consequences, the possibility of COVID-19-induced male infertility should not be neglected.

The role of selenium in type-2 diabetes mellitus and its metabolic comorbidities

This review addresses the role of the essential trace element, selenium, in type-2 diabetes mellitus (T2DM) and its metabolic co-morbidities, i.e., metabolic syndrome, obesity and non-alcoholic fatty liver disease. We refer to the dietary requirements of selenium and the key physiological roles of selenoproteins. We explore the dysregulated fuel metabolism in T2DM and its co-morbidities, emphasizing the relevance of inflammation and oxidative stress. We describe the epidemiology of observational and experimental studies of selenium in diabetes and related conditions, explaining that the interaction between selenium status and glucose control is not limited to hyperglycemia but extends to hypoglycemia. We propose that the association between high plasma/serum selenium and T2DM/fasting plasma glucose observed in many cross-sectional studies may rely on the upregulation of hepatic selenoprotein-P biosynthesis in conditions of hyperglycemia and insulin resistance. While animal studies have revealed potential molecular mechanisms underlying adverse effects of severe selenium/selenoprotein excess and deficiency in the pathogenesis of insulin resistance and β-cell dysfunction, their translational significance is rather limited. Importantly, dietary selenium supplementation does not appear to be a major causal factor for the development of T2DM in humans though we cannot currently exclude a small contribution of selenium on top of other risk factors, in particular if it is ingested at high (supranutritional) doses. Elevated selenium biomarkers that are often measured in T2DM patients are more likely to be a consequence, rather than a cause, of diabetes.

COVID-19 and Thyroid Diseases: A Bidirectional Impact

CONTEXT

COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which has become the most lethal and rapidly moving pandemic since the Spanish influenza of 1918-1920, is associated with thyroid diseases.

METHODS

References were identified through searches of PubMed and MEDLINE for articles published from Jan 1, 2019 to February 19, 2021 by use of the MeSH terms "hypothyroidism", "hyperthyroidism", "thyroiditis", "thyroid cancer", "thyroid disease", in combination with the terms "coronavirus" and "COVID-19". Articles resulting from these searches and references cited in those articles were reviewed.

RESULTS

Though preexisting autoimmune thyroid disease appears unlikely to render patients more vulnerable to COVID-19, some reports have documented relapse of Graves' disease (GD) or newly diagnosed GD about 1 month following SARS-CoV-2 infection. Investigations are ongoing to investigate molecular pathways permitting the virus to trigger GD or cause subacute thyroiditis (SAT). While COVID-19 is associated with non-thyroidal illness, it is not clear whether it also increases the risk of developing autoimmune hypothyroidism. The possibility that thyroid dysfunction may also increase susceptibility for COVID-19 infection deserves further investigation. Recent data illustrate the importance of thyroid hormone in protecting the lungs from injury, including that associated with COVID-19.

CONCLUSION

The interaction between the thyroid gland and COVID-19 is complex and bidirectional. COVID-19 infection is associated with triggering of GD and SAT, and possibly hypothyroidism. Until more is understood regarding the impact of coronavirus on the thyroid gland, it seems advisable to monitor patients with COVID-19 for new thyroid disease or progression of preexisting thyroid disease.

Aging and the hypothalamic-pituitary-thyroid axis

The world's population is increasingly aging, this noted particularly in the Western world where there are ever greater numbers of centenarians and those over 85 years. Given the immense importance of the thyroid gland for optimal health and the fact that morphological and functional changes in the hypothalamic-pituitary-thyroid (HPT) axis take place as a natural adaptation to the aging process, a clear distinction must be made in older individuals between these and the onset of disease. However, this is problematic since, frequently, subtle differences exist between them, making diagnosis a challenging task, especially as concerns subclinical disease. The newly emerging interdisciplinary field of geroscience offers the prospect of being used as a platform to investigate the effect of disrupted HPT function on functional capacity and cognitive ability among the aged, as well as the risk or onset of age-associated diseases, thus enhancing healthspan and lifespan. Because optimal functioning of the thyroid gland is a prerequisite for longevity as well as for mental and physical wellbeing, this review summarizes the recent scientific data regarding HPT and aging while discussing alternative and personalized treatment approaches to maintaining a healthy thyroid as a means to ensuring a long, active, and healthy life.

Selenium and at-risk pregnancy: challenges and controversies

Selenium (Se), an essential trace element, is inserted as selenocysteine into an array of functional proteins and forms the core of various enzymes that play a cardinal role in antioxidant defense mechanisms, in redox regulation, and in thyroid hormone metabolism. Variations in plasma Se are due to nutritional habits, geographic and ethnic differences, and probably to genetic polymorphisms, the latter still to be conclusively established. Se concentrations were reported to be low in women of reproductive age in the UK, decreasing further during pregnancy, this resulting in low plasma and placental antioxidant enzyme activities. Since low serum Se levels have been found in women with preeclampsia, it has been hypothesized that low maternal Se status during early gestation may be an indicator of preterm birth. Moreover, it is documented that Se administration during pregnancy tendentially reduced the markers of thyroid autoimmunity and the incidence of maternal hypothyroidism in the postpartum period. Importantly, low Se levels in pregnant women affect fetal growth and augment the risk of delivering a small-for-gestational age infant by reducing placental antioxidant defense, while low Se in the third trimester is thought to indicate increased demands by the placenta, an issue which requires further confirmation. There is evidently a need for double-blind, placebo-controlled studies to better determine the efficacy and safety of Se supplementation in pregnancy at high risk for complications, and for measurement of Se levels or of selenoprotein P, the most reliable parameter of Se status, particularly in selenopenic regions.

Evidence for a manifold role of selenium in infertility

This review aimed to assess the evidence from observational and interventional studies in humans and animals regarding the role of selenium (Se) in male and female infertility. As oxidative stress can seriously impair male, and possibly also female, reproductive functions, it can be speculated that the antioxidant properties of Se could constitute one of the pathways by which this element is involved in fertility. Specifically, there are strong indications that Se influences the growth, maturation, and replication of oocytes, though the precise mechanisms have not as yet been fully elucidated. Given that it is not clear at present which tissue sample (blood, serum, seminal plasma, sperm, or follicular fluid) renders the most accurate picture of Se concentration in terms of its role in reproduction, the data are still insufficient to recommend routine assessment of Se status in men and women seeking fertility. Nevertheless, the existing evidence, despite being of limited quantity and somewhat low quality, suggests that Se supplementation (< 200 μg/d) is possibly beneficial in men through its improvement of sperm motility. Well-designed, randomized control studies are needed to reveal the seemingly diverse protective/positive role of Se supplementation in men and women seeking fertility treatment.

50 years of the ETA: "the selenium connection"

The recent celebration of the 50 years of the ETA closely coincided with that of the 200 years since the discovery and description of selenium, an essential trace element for normal thyroid gland function and thus an adjuvant in the treatment of thyroid diseases. The aim of this commentary is to briefly outline the half centennial of the ETA while also signaling important moments in the history of selenium, developments in its availability round the world, details of its connection with thyroid function and, finally, its current and projected modes of application.

Correction to: Thyroid hormone therapy: past, present, and future

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

MANAGEMENT OF ENDOCRINE DISEASE: The role of rhTSH in the management of differentiated thyroid cancer: pros and cons

The use of recombinant human thyrotropin (rhTSH) testing in the diagnosis and therapy of differentiated thyroid cancer (DTC) has been adopted over the last two decades as an alternative to the classical thyroid hormone withdrawal avoiding the threat of hypothyroidism. Serum thyroglobulin (Tg) measurement is crucial for monitoring DTC patients over time. Until about a decade ago, optimal sensitivity of Tg assays for the detection of smaller disease foci required Tg measurement after thyrotropin (TSH) stimulation, carried out following thyroid hormone withdrawal or rhTSH administration. In very recent years, significant improvements in assay technology have resulted in highly sensitive Tg (hsTg) assays, sufficiently sensitive to obviate the need for rhTSH stimulation in most DTC patients. The aim of this paper is to review and discuss, via a 'pros and cons' approach, the current clinical role of rhTSH to stimulate radioiodine (RAI) uptake for treatment and/or imaging purposes and to increase the clinical sensitivity of Tg measurement for monitoring DTC patients when high-sensitive Tg assays are available.

Diagnosis and treatment of hypothyroidism in the elderly

The global population is aging with millions of people today living into their 90 s. Thyroid disease, particularly hypothyroidism, is widespread among all age groups, and it is expected to steadily increase as the population gets older. Clinical diagnosis of hypothyroidism is challenging, as the TSH reference range needs to be evaluated according to age, while evaluation of TSH levels must also take into account body weight and other variants such as polypharmacy, comorbidities, and general health condition. Since thyroid hormone has a potent regulatory effect on cholesterol metabolism, the possibility of thyroid dysfunction should be considered in cases of unexplained dyslipidemia. Once hypothyroidism has been confirmed, treatment requires caution, frequent cardiovascular monitoring, and individualized (precision) medicine. Treatment of subclinical hypothyroidism (SCH) in the elderly should be undertaken with care, guided by age and the degree of SCH: a TSH higher than 10 mU/l seems a reasonable threshold, though it should be regularly re-evaluated, while the LT4 dose needs to be tailored, taking into account the patient's health condition and the potential presence of dyslipidemia as well as other metabolic derangements.

Levothyroxine Dose Adjustment to Optimise Therapy Throughout a Patient's Lifetime

Levothyroxine is the standard therapy for patients with hypothyroidism, a condition that affects up to 5% of people worldwide. While levothyroxine therapy has substantially improved the lives of millions of hypothyroid patients since its introduction in 1949, the complexity of maintaining biochemical and clinical euthyroidism in patients undergoing treatment with levothyroxine cannot be underestimated. Initial dosing of levothyroxine can vary greatly and may be based on the amount of residual thyroid function retained by the patient, the body weight or lean body mass of the patient, and thyroid-stimulating hormone levels. As levothyroxine is usually administered over a patient’s lifetime, physiological changes throughout life will affect the dose of levothyroxine required to maintain euthyroidism. Furthermore, dose adjustments may need to be made in patients with concomitant medical conditions, in patients taking certain medications, as well as in elderly patients. Patients who have undergone any weight or hormonal changes may require dose adjustments, and the majority of pregnant women require increased doses of levothyroxine. Optimal treatment of hypothyroidism requires a partnership between patient and physician. The physician is tasked with vigilant appraisal of the patient’s status based on a thorough clinical and laboratory assessment and appropriate adjustment of their levothyroxine therapy. The patient in turn is tasked with medication adherence and reporting of symptomatology and any changes in their medical situation. The goal is consistent maintenance of euthyroidism, without the patient experiencing the adverse events and negative health consequences of under- or overtreatment.

Funding Merck.

Plain Language Summary Plain language summary available for this article.

European Perspective on 2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer: Proceedings of an Interactive International Symposium

BACKGROUND

The American Thyroid Association (ATA) management guidelines for patients with thyroid nodules and differentiated thyroid cancer (DTC) are highly influential practice recommendations. The latest revision appeared in 2015 ("ATA 2015"). These guidelines were developed predominantly by North American experts. European experts frequently have different perspectives, given epidemiological, technological/methodological, practice organization, and medicolegal differences between the respective regions.

SUMMARY

Divergent viewpoints were the focus of an invited symposium organized by the European Association of Nuclear Medicine involving 17 European thyroidologists, four ATA Guidelines Taskforce members, and an audience of 200 international experts. The group discussed the preoperative assessment of thyroid nodules, surgery and the role of pathology, radioiodine (RAI) therapy (RAIT), the assessment of initial therapy and dynamic risk stratification, and the treatment of persistent disease, recurrences, and advanced thyroid cancer. The dialogue resulted in this position paper contrasting European and ATA 2015 perspectives on key issues. One difference pertains to the permissiveness of ATA 2015 regarding lobectomy for primary tumors ≤4 cm. European panelists cited preclusion of RAIT, potential need for completion thyroidectomy, frequent inability to avoid chronic thyroid hormone replacement, and limitations of supportive evidence as arguments against widely applying lobectomy. Significant divergence involved ATA 2015's guidance regarding RAIT. European panelists favored wider use of postoperative RAIT than does ATA 2015. Rationales included the modality's association with favorable patient outcomes and generally limited toxicity, and lack of high-quality evidence supporting withholding RAIT. Additionally, European panelists favored recombinant human thyrotropin (rhTSH) in more settings than does ATA 2015, citing avoidance of hypothyroid morbidity and quality-of-life impairment, without apparent sacrifice in oncologic outcomes. Based on clinical evidence plus theoretical advantages, European experts advocated dosimetric versus fixed-activity RAIT approaches for advanced DTC. European panelists noted that the ATA 2015 risk-stratification system requires information sometimes unavailable in everyday practice. ATA 2015 recommendations regarding RAI-refractory DTC should consider potential palliative benefits of RAIT in patients who also have RAI-susceptible lesions.

CONCLUSIONS

European panelists suggested modifications to approximately one-third of ATA 2015 recommendations. Varying European and ATA 2015 perspectives can stimulate analysis and discussion of the literature and performance of primary research to resolve discrepant recommendations and potentially improve patient outcomes.

The catalytic role of iodine excess in loss of homeostasis in autoimmune thyroiditis

PURPOSE OF REVIEW

To review the latest developments concerning the role of iodine in the pathophysiology of autoimmune thyroiditis.

RECENT FINDINGS

Recent studies have provided evidence that in areas with excess iodine intake, increased incidence of autoimmune thyroiditis marked by high titers of thyroid peroxidase and thyroglobulin antibodies has occurred. Investigations in the NOD.H2h4 mouse, a strain prone to AIT, showed that they are better adapted to the Wolff-Chaikoff effect.

SUMMARY

To provide an overview of the studies conducted during the last few years implicating iodine in the development and manifestation of autoimmune thyroiditis.

A Renewed Focus on the Association Between Thyroid Hormones and Lipid Metabolism

Thyroid dysfunction, manifesting as either overt or subclinical hypothyroidism, negatively affects lipid metabolism: this leads to hypercholesterolemia which progressively increases the risk for cardiovascular disease and, potentially, mortality. Hypercholesterolemia in hypothyroidism is mainly due to a reduction in low-density lipoprotein (LDL) receptor activity, this accompanied by concomitant diminishing control by triiodothyronine (T3) of sterol regulatory element-binding protein 2 (SREBP-2), which modulates cholesterol biosynthesis by regulating rate-limit degrading enzyme 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA) activity. Recently, 3,5-diiodothyronine (T2), a natural thyroid hormone derivative, was found to repress the transcription factor carbohydrate-response element-binding protein (ChREBP) and also to be involved in lipid catabolism and lipogenesis, though via a different pathway than that of T3. While thyroid hormone could therapeutically reverse the dyslipidemic profile commonly occurring in hypothyroidism, it should be borne in mind that the potency of the effects may be age-and sex-dependent. Thyroid hormone administration possibly also sustains and enhances the efficacy of hypolipidemic drugs, such as statins, ezetimibe and proprotein convertase subtilisin/kexin type 9 (PCSK9), in patients with dyslipidemia and hypothyroidism.

Thyroid Function in Aging: A Discerning Approach

Thyroid disease, increasingly common among the general population, is also rising among the elderly, which, given that the global population is aging, constitutes a serious public health issue that needs to be urgently addressed. The most common thyroid disease in younger and older individuals alike is hypothyroidism, including subclinical (SCH) and overt disease. Since TSH tends to increase with age due to intrinsic changes of thyroid metabolism and the gradual resetting of the hypothalamic-pituitary-thyroid axis, the diagnosis of "true" hypothyroidism is challenging, another difficulty being distinguishing disease-specific from aging-associated clinical symptoms. Hypothyroidism in the elderly may cause or exacerbate macrocytic anemia, hypercholesterolemia and kidney dysfunction, therefore careful clinical and biochemical control is necessary. Meanwhile, as an increase of TSH in the old and very old has been associated with longevity, a resetting of the TSH normal range according to age is strongly required before any diagnosis is made and treatment is implemented. Levothyroxine, which remains the treatment of choice, should be initiated in the old at TSH>10 mIU/l, starting with 25 μg/daily followed by cautious upward titration. Recent data (the TRUST study) revealed that treatment of SCH in the elderly does not improve hypothyroid symptoms and the tiredness score when compared with a placebo group. Hyperthyroidism is associated with increased mortality in the aged, this dependent upon type and adequacy of treatment. Treatment should be seriously considered in older patients who have endogenous subclinical hyperthyroidism with a TSH between 0.1 and 0.4 mIU/L, with regular monitoring being strongly advised.

Impaired Metabolism of Selenomethionine in Graves' Disease: A Biokinetics Study of Soft Gel Capsule Formulation

Patients with Graves' disease are known to have low selenium (Se) status, Se supplementation resulting in clinical and biochemical improvement. Selenomethionine (SeMet) in a new soft gel capsule formulation was used in a pilot study in 6 patients with acute Graves' disease and low selenium levels (61.3±12.9 μg/l) before and in 4/6 patients 3 months after combined treatment with methimazole and SeMet 200 μg/day (113.3±46.3 μg/l), as well as in 6 euthyroid controls (82±11.8 μg/l). The biokinetics were studied following ingestion of 200 μg SeMet (single dose) soft gel capsule, Se serum concentrations being measured at various time points within 24 h. Se levels rose variably in all patients and controls. While levels peaked in all subjects following 8 h of intake, the increase was somewhat slower in acute hyperthyroidism as compared to 3 months later when these patients had been rendered euthyroid, this possibly due to derangement of Se storage capacity by SEPP or increased requirements in the acute phase of the disease, leading to depletion of the trace element. The compound was shown to be bioavailable and safe and patients treated for 3 months exhibited higher Se levels at the different time points. These findings are of major importance for sufferers of GD since they indicate that early Se supplementation, with its beneficial antioxidant impact on inflammatory activity, could slow, or possibly even forestall, the clinical progression of the disease.

Multifocality in Sporadic Medullary Thyroid Carcinoma: An International Multicenter Study

BACKGROUND

Current surgical standard of care in sporadic medullary thyroid carcinoma (sMTC) consists of a minimum of total thyroidectomy with central neck dissection. Some have suggested thyroid lobectomy with isthmusectomy and central neck dissection for patients with sMTC, given their lower frequency of bilateral disease, although this topic has not been thoroughly studied. This study assessed the prevalence of multifocality in sMTC via a large international multi-institutional retrospective review to quantify this prevalence, including the impact of geography, to assess more accurately the risks associated with alternative surgical approaches.

METHODS

A retrospective chart review of sMTC patients from 11 institutions over 29 years (1983-2011) was undertaken. Data regarding focality, extent of disease, RET germline analysis plus family and clinical history for multiple endocrine neoplasia type 2 (MEN2), and demographic data were collected and analyzed.

RESULTS

Patients from four continents and seven countries were included in the sample. Data for 313 patients with documented sMTC were collected. Of these, 81.2% were confirmed with negative RET germline testing, while the remaining 18.8% demonstrated a negative family history and no manifestations of MEN2 syndromes other than MTC. Bilateral disease was identified in 17/306 (5.6%) patients, while multifocal disease was noted in 50/312 (16.0%) sMTC patients. When only accounting for germline negative patients, these rates were not significantly different (5.6% and 17%, respectively). Among them, when disease was unifocal in the ipsilateral lobe and isthmus, bilateral disease was present in 6/212 (2.8%) cases. When disease was multifocal in the ipsilateral lobe or isthmus, then bilateral disease was present in 8/37 (21.6%) cases (p < 0.001). No geographic differences in focality were identified.

CONCLUSIONS

The 5.6% prevalence of bilateral foci in sMTC suggests that total thyroidectomy should remain the standard of care for initial surgery, as less complete thyroid surgery may fail to address fully the primary site of disease. Whether ipsilateral tumor focality should be an independent factor determining the need for completion thyroidectomy when sMTC is diagnosed after hemithyroidectomy remains to be determined.

Thyroid hormones: a potential ally to LDL-cholesterol-lowering agents

L-thyroxine (LT4) treatment of hypothyroidism, particularly in patients with thyroid- stimulating hormone (TSH) >10mU/L, results in improved lipid profile, as LT4 stimulates low-density lipoprotein cholesterol (LDL-C) degradation and the conversion of cholesterol in bile acids by inducing LDL-receptor and 7 alpha hydroxylase expression, respectively. Statins decrease total cholesterol (TC) and LDL-C mainly by suppressing 3-hydroxy-3-methylglutaryl coenzyme A activity. Therefore, the addition of statins to LT4 treatment, following the reversal of hypothyroidism, acts synergistically and forms a powerful treatment modality in patients with this condition whose serum lipids have not achieved the target. Statin add-on therapies, such as ezetimibe (EZE) and the recently approved proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors, in conjunction with LT4 therapy, produce an even more favorable profile. Ezetimibe blocks the intestinal absorption of cholesterol, while in patients with heterozygous familiar hyperlipidemia, PCSK9 inhibitors suppress PCSK9, thereby promoting LDL-C degradation. The synergy of these drugs results in a far better lipidemic profile than when each drug is administered alone, with LT4 treatment clearly enhancing, in many respects, the efficacy of therapy.

NEW INSIGHTS INTO THE HYPOTHALAMIC-PITUITARY-THYROID AXIS

The discovery of thyrotropin releasing hormone (TRH) in 1969 was the definitive step in decoding the hypothalamic-pituitary thyroid (HPT) axis, thereby opening up the era of neuroendocrinology, while it also revolutionized the diagnostic and therapeutic approach to patients with thyroid diseases. TRH, produced in the hypothalamus, is the central regulator of the HPT. It functions via neurons originating in the paraventricular nucleus (PVN), which integrates multiple neuronal and humoral signals and resets the HPT axis according to variations of external and internal environmental conditions. The TRH activates TSH in the pituitary that stimulates the secretion of thyroxine from thyroid which, in turn, exerts a negative feedback on TSH and TRH secretion. However, various factors are involved in the regulation of the HPT axis. Leptin has both indirect and direct effects on TRH regulation, the former by regulating agouti-related peptide (AGRP) in the arcuate nucleus (ARN) that antagonizes the α-MSH stimulatory activity on pro-TRH gene expression in the PVN, and the latter by stimulating hypothalamic TRH expression, TRH transcription via stimulation of pro-convertase 1 and 2 expression, which lead to enhanced processing of pro-TRH into TRH. The interplay of TRH with leptin and the recently reported influence of ghrelin on the HPT axis can alter the setpoint of the axis. The polyphenol resveratrol, as recently observed, exerts an anxiolytic and antidepressant activity in subclinical hypothyroid (SCH) rats. Resveratrol, by decreasing both TSH and TRH mRNA expression, regulates the HPT axis, while in parallel it regulates the Wnt/β-catenin pathway in the hippocampus. These findings open up possibilities for the therapeutic use of resveratrol as coadjuvant, especially in overt and SCH states marked by anxiety and depression. The clinician should be aware of clinical changes that can invalidate the normal regulation of the HPT axis, the most commonly observed being medications and comorbidities.

Toxic chemicals and thyroid function: hard facts and lateral thinking

Increasing quantities of evidence-based data incriminate a large number of environmental pollutants for toxic effects on the thyroid. Among the many chemical contaminants, halogenated organochlorines and pesticides variably affect the hypothalamic-pituitary-thyroid axis and disrupt thyroid function. PCBs and their metabolites and PBDEs bind to thyroid transport proteins, such as transthyretin, displace thyroxine, and disrupt thyroid function. Meanwhile, at the molecular level, PCB congeners may activate phosphorylation of Akt, p-Akt, and forkhead box O3a (FoxO3a) protein resulting in inhibition of the natrium/iodide symporter. Given therefore the growing concern developing around these multiple toxic chemicals today invading numerous environments and their long-term deleterious effects not only on the thyroid but also on general health, we strongly advocate their strict regulation and, moreover, their gradual reduction. A good degree of "lateral thinking", we feel, will lead to a use of chemicals that will enhance life while concurrently carefully protecting the environment.

The Role of Iodine and Selenium in Autoimmune Thyroiditis

Iodine and selenium (Se) are both essential elements to thyroid hormone economy, while they represent key players in the development of autoimmune thyroiditis.Chronic high iodine intake has been associated in various studies with increased frequency of autoimmune thyroiditis. In susceptible individuals, iodine excess increases intra-thyroid infiltrating Th17 cells and inhibits T regulatory (TREG) cells development, while it triggers an abnormal expression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in thyrocytes, thus inducing apoptosis and parenchymal destruction. As was shown in a mouse model, high iodine supply leads to changes in the immunogenicity of the thyroglobulin molecule, upregulation of vascular intercellular adhesion molecule-1 (ICAM-1), and reactive oxygen species (ROS) generation in the thyrocytes. Serum Se levels were found decreased in Hashimoto thyroiditis and especially in Graves' disease as well as in thyroid-associated ophthalmopathy patients, the levels being related to the pathogenesis and outcome. Selenium is strongly involved, via the variable selenoproteins, in antioxidant, redox, and anti-inflammatory processes. Selenium enhances CD4+/CD25 FOXP3 and T regulatory cells activity while suppressing cytokine secretion, thus preventing apoptosis of the follicular cells and providing protection from thyroiditis. Selenium supplementation may be useful in autoimmune thyroid diseases, though, while usually well-tolerated, it should not be universally recommended, and it is also likely to be helpful for those with low Se status and autoimmunity. Broadly speaking, the achievement and maintenance of "selenostasis" as well as adequate urinary iodine excretion are mandatory to control disease, while, putatively, they may additionally be critical to preventing disease.

Selenium: an element for life

This review aims to illustrate the importance of selenium (Se) for maintenance of overall health, especially for the thyroid, immunity, and homeostasis. Furthermore, it outlines the role of Se in reproduction and in virology and discusses the effects of Se supplementation in critical illness. The multifaceted aspects of this essential nutrient have attracted worldwide clinical and research interest in the last few decades. Se exerts its activity in the form of the aminoacid selenocysteine incorporated in selenoproteins. The impact of Se administration should be considered in relation to its apparent U shaped effects, i.e., exhibiting major advantages in Se-deficient individuals but specific health risks in those with Se excess. Addition of selenium to the administration of levothyroxine may be useful in patients with low Se intake and with mild-form or early-stage Hashimoto's thyroiditis (HT). Serum Se concentration (possibly also at tissue level) decreases in inflammatory conditions and may vary with the severity and duration of the inflammatory process. In such cases, the effect of Se supplementation seems to be useful and rational. Meanwhile, Se's ability to improve the activity of T cells and the cytotoxicity of natural killer cells could render it effective in viral disease. However, the evidence, and this should be stressed, is at present conflicting as to whether Se supplementation is of benefit in patients with HT, though there are indications that it is advantageous in cases of mild/moderate Graves' Orbitopathy. The role of Se in type 2 diabetes mellitus (T2DM) is ambiguous, driven by both Se intake and serum levels. The evidence that insulin and glycaemia influence the transport and activity of Se, via regulatory activity on selenoproteins, and that high serum Se may have a diabetogenic effect suggests a 'Janus-effect' of Se in T2DM. Though the evidence is not as yet clear-cut, the organic form (selenomethionine), due to its pharmacokinetics, is likely to be more advantageous in long-term prevention, and supplementation efforts, while the inorganic form (sodium selenite) has proven effective in an acute, e.g., sepsis, clinical setting. Recent data indicate that functional selenoprotein single-nucleotide polymorphisms (SNPs) may interfere with Se utilization and effectiveness.

Chemical contamination and the thyroid

Industrial chemical contaminants have a variable impact on the hypothalamic-pituitary-thyroid axis, this depending both on their class and on confounding factors. Today, mounting evidence is pointing to the role of environmental factors, and specifically EDCs, in the current distressing upsurge in the incidence of thyroid disease. The unease is warranted. These substances, which are nowadays rife in our environments (including in foodstuffs), have been shown to interfere with thyroid hormone action, biosynthesis, and metabolism, resulting in disruption of tissue homeostasis and/or thyroid function. Importantly, based on the concept of the "nonmonotonic dose-response curve", the relationship between dose and effect has often been found to be nonlinear. Thus, small doses can induce unpredictable, adverse effects, one case being polychlorinated biphenyls (PCBs), of which congener(s) may centrally inhibit the hypothalamic-pituitary-thyroid axis, or dissociate thyroid receptor and selectively affect thyroid hormone signaling and action. This means that PCBs can act as agonists or antagonists at the receptor level, underlining the complexity of the interaction. This review highlights the multifold activity of chemicals demonstrated to cause thyroid disruption. It also represents a call to action among clinicians to undertake systematic monitoring of thyroid function and registering of the classes of EDs and additionally urges broader scientific collaborations to clarify these chemicals' molecular mechanisms of action, substances whose prevalence in our environments is disrupting not only the thyroid but all life on earth.

Selenium and Inflammation— Potential Use and Future Perspectives

The essential trace element selenium (Se) is constitutively incorporated as selenocysteine, in proteins, among others in antioxidative selenoproteins, such as glutathione peroxidase(s) and thioredoxin reductase. Since chronic inflammation is thought to deplete Se stores in the body, Se supplementation should be considered in prolonged inflammatory states, Se being the trace element the most affected in chronic or low-grade inflammation. Se administration might also be beneficial in bacterial and viral diseases as well as metabolic and autoimmune diseases. In order to maintain a Se steady state, or “selenostasis,” Se supplementation, via either diet or compounds, is required to preserve the activity of selenoproteins in antioxidative and redox processes. Importantly, Se could play a pivotal role in the maintenance of homeostasis in infected tissues by inhibiting the proinflammatory toll-like receptor nuclear factor kappa-light-chain-enhancer of activated B cells signaling pathway and counteracting proinflammatory cytokine action. Finally, while Se status shows considerable promise as a valid marker of inflammatory and autoimmune disease, new functional Se nanoparticles and highly bioavailable selenomethionine compounds will in all probability provide a more efficacious and reliable intervention tool in both preventive and therapeutic disease management.

Cardiovascular Risk in Patients with Subclinical Hypothyroidism

Subclinical hypothyroidism (SCH) has been associated with increased cardiovascular mortality due to adverse effects mainly on lipids and blood pressure (BP). There is evidence that SCH, especially in patients with thyroid-stimulating hormone (TSH) >10mU/l, may increase cardiovascular risk. Some uncertainty exists regarding the association of SCH with BP; however, that the coexistence of SCH with BP and hypercholesterolaemia has a negative cardiovascular impact is beyond doubt. Insulin resistance, by modulating various risk factors including coagulation, may potentially increase cardiovascular risk. Periodic health examinations including screening has been advised in patients >35 years of age, while treatment with thyroxine should be tailored to each patient.

Hypothyroidism and depression: salient aspects of pathogenesis and management

Hypothyroidism has been linked to depression as there is irrefutable evidence that it triggers affective disease and psychic disorders. Depressive patients have a higher frequency of hypothyroidism and patients with hypothyroidism have a higher occurrence of depressive syndrome. Hypothyroidism exhibits considerable alterations in blood flow and glucose metabolism in the brain. Furthermore, patients with major depression may have structural abnormalities of the hippocampus that can affect memory performance. Thyroid peroxidase antibodies have, moreover, been positively associated with trait markers of depression. Depressive symptomatology is variable and is influenced by susceptibility and the degree, though not always, of thyroid failure. In addition, glucose homeostasis and rapid weight loss have been associated to thyroid hormones and increased depressive symptoms. Thyroxine treatment in patients older than 65 years does not improve cognition. In contrast, T3 administration is the therapy of choice in patients with resistance to antidepressive drugs, and especially to SSIR. Genetic variants of thyroid hormone transporters or of deiodinases I and II may predispose to depression and, therefore, a personalized approach should be implemented.

2013 ETA Guideline: Management of Subclinical Hypothyroidism

Subclinical hypothyroidism (SCH) should be considered in two categories according to the elevation in serum thyroid-stimulating hormone (TSH) level: mildly increased TSH levels (4.0-10.0 mU/l) and more severely increased TSH value (>10 mU/l). An initially raised serum TSH, with FT4 within reference range, should be investigated with a repeat measurement of both serum TSH and FT4, along with thyroid peroxidase antibodies, preferably after a 2- to 3-month interval. Even in the absence of symptoms, replacement therapy with L-thyroxine is recommended for younger patients (<65-70 years) with serum TSH >10 mU/l. In younger SCH patients (serum TSH <10 mU/l) with symptoms suggestive of hypothyroidism, a trial of L-thyroxine replacement therapy should be considered. For such patients who have been started on L-thyroxine for symptoms attributed to SCH, response to treatment should be reviewed 3 or 4 months after a serum TSH within reference range is reached. If there is no improvement in symptoms, L-thyroxine therapy should generally be stopped. Age-specific local reference ranges for serum TSH should be considered in order to establish a diagnosis of SCH in older people. The oldest old subjects (>80-85 years) with elevated serum TSH ≤10 mU/l should be carefully followed with a wait-and-see strategy, generally avoiding hormonal treatment. If the decision is to treat SCH, then oral L-thyroxine, administered daily, is the treatment of choice. The serum TSH should be re-checked 2 months after starting L-thyroxine therapy, and dosage adjustments made accordingly. The aim for most adults should be to reach a stable serum TSH in the lower half of the reference range (0.4-2.5 mU/l). Once patients with SCH are commenced on L-thyroxine treatment, then serum TSH should be monitored at least annually thereafter.

The interconnections between obesity, thyroid function, and autoimmunity: the multifold role of leptin

BACKGROUND

There is increasing evidence that changes in thyroid function are associated with obesity, a condition associated with a chronic low-grade state of inflammation. Meanwhile, recent data have disclosed a relation between obesity and thyroid autoimmunity, with the adipocyte hormone leptin appearing to be the key factor linking these two conditions.

SUMMARY

Leptin has variably been implicated in thyroid function, while recent findings suggest that leptin resistance may mitigate leptin deficiency and enhance autoimmunity in obese subjects via mechanisms operating independently of thyroid function. The development of resistance to the weight-lowering effects of leptin in obesity might well be initiated by activation of inflammatory signaling, which substantially contributes to the derangement of immune response and propagation of autoimmunity in susceptible individuals.

CONCLUSIONS

Regulation of inflammasome-derived cytokines in obesity is an important step in controlling the trigger of thyroid autoimmunity. The clarification of the pathways may offer innovative therapeutic targets in obesity and thyroid autoimmunity.

Hormones as doping in sports

Though we may still sing today, as did Pindar in his eighth Olympian Victory Ode, "… of no contest greater than Olympia, Mother of Games, gold-wreathed Olympia…", we must sadly admit that today, besides blatant over-commercialization, there is no more ominous threat to the Olympic games than doping. Drug-use methods are steadily becoming more sophisticated and ever harder to detect, increasingly demanding the use of complex analytical procedures of biotechnology and molecular medicine. Special emphasis is thus given to anabolic androgenic steroids, recombinant growth hormone and erythropoietin as well as to gene doping, the newly developed mode of hormones abuse which, for its detection, necessitates high-tech methodology but also multidisciplinary individual measures incorporating educational and psychological methods. In this Olympic year, the present review offers an update on the current technologically advanced endocrine methods of doping while outlining the latest procedures applied-including both the successes and pitfalls of proteomics and metabolomics-to detect doping while contributing to combating this scourge.

Clinical comments related to medullary thyroid cancer diagnosis and management

Background

The American Thyroid Association (ATA) and more recently the European Thyroid Association (ETA) Guidelines on diagnosis and treatment of medullary thyroid carcinoma (MTC) have provided an excellent tool which was formerly lacking in the field of management of MTC. However, some relevant clinical questions, as the use of somatostatin analogues in the treatment of MTC and the management of pregnant patients with MTC, which were recommended in the guidelines, have been lately extensively revised. Moreover the current issue whether GLP-1 (a glucagon-like peptide-1) analogue is associated with MTC has only superficially been analyzed.

Methods

Publications have been retrieved in MEDLINE at Pubmed (there is no fix date retrospectively) up to October 2012 using the terms “medullary thyroid carcinoma”, “somatostatin”, “pregnancy” and “incretins”. The recommendations made by ATA and ETA were considered.

Conclusions

There are no data supporting the application of somatostatin analogues in the treatment of MTC, while thyroid cancer during or after pregnancy has no impact on the prognosis of disease or on the outcome of pregnancy. However, women with MEN 2 should be carefully controlled before any planned or during any unplanned pregnancy. In contrast to animal studies, there are no consistent human data supporting a stimulatory effect of GLP-1 receptor activation by liraglutide, an incretin mimetic, on calcitonin levels, though establishment of a registry and further studies are required to exclude any association between GLP-1 analogue and MTC.

The effect of thyroid disorders on lipid levels and metabolism

Thyroid hormones regulate cholesterol and lipoprotein metabolism, whereas thyroid disorders, including overt and subclinical hypothyroidism, considerably alter lipid profile and promote cardiovascular disease. Good evidence shows that high thyroid-stimulating hormone (TSH) is associated with a nonfavorable lipid profile, although TSH has no cutoff threshold for its association with lipids. Thyromimetics represent a new class of hypolipidemic drugs: their imminent application in patients with severe dyslipidemias, combined or not with statins, will improve the lipid profile, potentially accelerate energy expenditure and, as a consequence, vitally lessen the risk of cardiovascular disease.

Resveratrol and its impact on aging and thyroid function

Resveratrol, the naturally occurring polyphenolic compound characterized by anti-oxidative, anti-inflammatory and apoptotic properties, appears to contribute substantially to cardioprotection and cancer-prevention. In addition, resveratrol is believed to regulate several biological processes, mainly metabolism and aging, by modulating the mammalian silent information regulator 1 (SIRT1) of the sirtuin family. Resveratrol may arrest, among various tumors, cell growth in both papillary and follicular thyroid cancer by activation of the mitogen-activated protein kinase (MAPK) signal transduction pathway as well as increase of p53 and its phosphorylation. Finally, resveratrol also influences thyroid function by enhancing iodide trapping and, by increasing TSH secretion via activation of sirtuins and the phosphatidylinositol- 4-phosphate 5 kinase γ (PIP5Kγ) pathway, positively affects metabolism.