Role of iodine in thyroid physiology

Exploring mammalian heme peroxidases: A comprehensive review on the structure and function of myeloperoxidase, lactoperoxidase, eosinophil peroxidase, thyroid peroxidase and peroxidasin

The peroxidase family of enzymes is a ubiquitous cluster of enzymes primarily responsible for the oxidation of organic and inorganic substrates. The mammalian heme peroxidase subfamily is characterized by a covalently linked heme prosthetic group which plays a key role in the oxidation of halides and psuedohalides into their respective hypohalous acid and hypothiocyanous acid under the influence of H2O2 as substrate. The members of the heme peroxidase family include Lactoperoxidase (LPO), Eosinophil peroxidase (EPO), Myeloperoxidase (MPO), Thyroid peroxidase (TPO) and Peroxidasin (PXDN). The biological activity of LPO, MPO and EPO pertains to antibacterial, antifungal and antiviral while TPO is involved in the biosynthesis of the thyroid hormone and PXDN helps maintain the ECM. While these enzymes play several immunomodulatory roles, aberrations in their activity have been implicated in diseases such as myocardial infarction, asthma and Alzheimer's amongst others. The sequence and structural similarities amongst the members of the family are strikingly high while the substrate specificities and subcellular locations vary. Hence, it becomes important to provide a consortium of information regarding the members to study their biochemical, pathological and clinical function.

The global burden, trends, and inequalities of individuals with developmental and intellectual disabilities attributable to iodine deficiency from 1990 to 2019 and its prediction up to 2030

Objective

The objective of this study was to assess the global burden of disease for developmental and intellectual disabilities caused by iodine deficiency from 1990 to 2019.

Methods

Using data from the global burden of disease (GBD) 2019, we conducted a cross-country inequity analysis to examine the worldwide burden of developmental and intellectual disabilities caused by the issue of iodine deficiency from 1990 to 2019. Absolute and relative inequality were assessed by the slope index of inequality and the concentration index, respectively. After summarising the latest evidence, we also projected the age-standardized prevalence and years lived with disability (YLD) rates up to 2030 using the BAPC and INLA packages in R statistical software.

Results

In 2019, the global age-standardized prevalence and YLD rates for developmental and intellectual disabilities due to iodine deficiency were 22.54 per 100,000 population (95% UI 14.47 to 29.23) and 4.12 per 100,000 population (95% UI 2.25 to 6.4), respectively. From 1990 to 2019, the age-standardized prevalence and YLD rates of developmental and intellectual disabilities due to iodine deficiency decreased significantly. Geographic distribution showed that areas with lower socio-demographic indices (SDI) were the most affected. The correlation between higher SDI and lower prevalence highlights the role of economic and social factors in the prevalence of the disease. Cross-national inequity analysis shows that disparities persist despite improvements in health inequalities. In addition, projections suggest that the disease burden may decline until 2030.

Conclusion

This research underscores the necessity for targeted interventions, such as enhancing iodine supplementation and nutritional education, especially in areas with lower SDI. We aim to provide a foundation for policymakers further to research effective preventative and potential alternative treatment strategies.

Risks of Iodine Excess

Iodine is a micronutrient that is required for thyroid hormone synthesis. The iodide cycle in thyroid hormone synthesis consists of a series of transport, oxidation, organification, and binding/coupling steps in thyroid follicular cells. Common sources of iodine include the consumption of an iodine-rich diet or iodine fortified foods, the administration of amiodarone, iodine-containing supplements, or iodinated contrast media, and other miscellaneous sources. Methods to assess population iodine status include the measurement of urinary iodine concentrations, blood thyroglobulin levels, prevalence of elevated neonatal TSH levels, and thyroid volume. Although excessive iodine intake or exposure is generally well tolerated, an acute iodine load may result in thyroid dysfunction (hypothyroidism or hyperthyroidism) in certain susceptible individuals due to the failure to escape from the Wolff-Chaikoff effect and to the Jod-Basedow phenomenon, respectively. In this review, we discuss the associations between excessive iodine intake or exposure, with particular focus on iodinated contrast media as a common source of excess iodine in healthcare settings, and risks of incident thyroid dysfunction. We also summarize the risks of iodine excess in vulnerable populations and review current guidelines regarding the screening and monitoring of iodinated contrast-induced thyroid dysfunction. Finally, we discuss the long-term potential nonthyroidal health risks associated with iodine excess and suggest the need for more data to define safe upper limits for iodine intake, particularly in high-risk populations.

A Fatal Consequence: Amiodarone-Induced Multiorgan Toxicity

Amiodarone is commonly used nowadays for the treatment of atrial fibrillation (AF). The wide use of this medication has led to the occurrence of adverse events, including pulmonary toxicity, hepatotoxicity, thyroid dysfunction, and many others. Higher doses of Amiodarone of ≥400 mg/day have been linked to increased complications. We present a case of a 70-year-old male with multivessel coronary artery disease (CAD) with ischemic cardiomyopathy and severe peripheral artery disease (PAD) who underwent an elective left femoral to posterior tibial bypass surgery followed by percutaneous coronary intervention (PCI) complicated by new-onset AF. The patient was loaded with 150 mg of intravenous (IV) Amiodarone followed by 360 mg infusion over six hours for chemical cardioversion. The patient was then maintained on oral Amiodarone 400 mg/day until the day of presentation when he complained of progressive dyspnea. Imaging was significant for diffuse ground glass opacities and interstitial thickening. The echocardiogram revealed an improved ejection fraction (EF) of 40% from 20%. The patient had worsening oxygenation despite adequate IV diuresis and developed severe acute respiratory distress syndrome (ARDS) requiring mechanical ventilation (MV). A bronchoscopy with bronchoalveolar lavage (BAL) showed diffuse alveolar hemorrhage (DAH) with a high lymphocyte count and negative infectious disease testing. Lab tests revealed elevated liver enzyme levels. There were also changes in thyroid function from baseline with elevated free T4 at 1.83 ng/dL (0.8-1.4 ng/dL), suppressed thyroid stimulating hormone (TSH) at 0.109 mIU/mL (0.4-4 mIU/mL), negative anti-thyroglobulin (TG) antibodies, and anti-thyroid peroxidase (TPO) antibodies indicating a type 2 Amiodarone-induced thyrotoxicosis. Unfortunately, the patient's condition deteriorated further despite appropriate treatment, and it was ultimately followed by his demise. Severe, fatal cases of Amiodarone toxicity are scarce, but more reports are being seen. We strongly believe clinicians should have a high index of suspicion for Amiodarone-related adverse events in elderly males with cardiopulmonary comorbidities. It is imperative to have an increased understanding, greater vigilance, and closer monitoring of pulmonary function tests (PFTs), laboratory tests, and imaging studies.

Drug-induced hypothyroidism in tuberculosis

INTRODUCTION

Adverse reactions to tuberculosis treatment can impact patient adherence and prognosis. Hypothyroidism is a frequent adverse reaction caused using ethionamide, prothionamide, and para-aminosalicylic acid and is often underdiagnosed.

AREAS COVERED

We searched Scielo, Scopus, and EMBASE databases, including 67 articles. Antitubercular drug-induced hypothyroidism has a prevalence of 17%. It occurs after 2 to 3 months of treatment and resolves within 4 to 6 weeks after discontinuation. It is postulated to result from the inhibition of thyroperoxidase function, blocking thyroid hormone synthesis. Symptoms are nonspecific, necessitating individualized thyroid-stimulating hormone measurement for detection. Specific guidelines for management are lacking, but initiation of treatment with levothyroxine, as is customary for primary hypothyroidism, is recommended. Discontinuation of antitubercular drugs is discouraged, as it may lead to unfavorable consequences.

EXPERT OPINION

Antitubercular drug-induced hypothyroidism is more common than previously thought, affecting one in six MDR-TB patients. Despite diagnostic and treatment recommendations, implementation is hindered in low-income countries due to the lack of certified laboratories. New drugs for tuberculosis treatment may affect thyroid function, requiring vigilant monitoring for complications, including hypothyroidism.

Association between Consumption of Iodine-Rich Foods and Thyroid Cancer Prevalence: Findings from a Large Population-Based Study

The influence of iodine-rich foods on thyroid cancer (TC) risk remains inadequately understood. Therefore, we aimed to comprehensively investigate the relationship between three iodine-rich food groups and TC prevalence using extensive data from a large Korean population. We assessed the dietary intake of 169,057 participants in the Korean Genome and Epidemiology Study (2004-2013) using a food frequency questionnaire. The top-three iodine-rich food groups (including egg, seaweed, and dairy) were selected based on Korean dietary reference intakes and categorized by weekly consumption frequency. We conducted multiple logistic regression models to examine the relationship between food consumption and TC prevalence. After adjusting for confounding factors, higher seaweed consumption (>5 times/week) was significantly associated with lower TC prevalence (odds ratio [OR], 95% confidence interval [CI] = 0.42, 0.32-0.56, p-value < 0.001). In contrast, compared with moderate dairy consumption (3-4 times/week), lower dairy product intake (<1 time/week) was associated with higher TC prevalence (OR, 95% CI = 1.32, 1.05-1.67, p-value = 0.017). Our findings suggest that sufficient seaweed consumption may offer protection against TC, and incorporating dairy products into the diet may lower TC incidence in the Korean population. The most significant limitations of our study are the absence of 24 h urine samples for iodine status assessment and the lack of clinical data on the diagnosis of thyroid cancer.

Transcriptomic profiling of the response to excess iodide in Keap1 hypomorphic mice reveals new gene-environment interactions in thyroid homeostasis

Iodide plays a pivotal role in thyroid homeostasis due to its crucial involvement in thyroid hormone biosynthesis. Exposure to pharmacological doses of iodide elicits in the thyroid an autoregulatory response to preserve thyroid function, as well as an antioxidant response that is mediated by the Keap1/Nrf2 signaling pathway. The objective of the present study was to investigate the transcriptional response of the thyroid to excess iodide in a background of enhanced Nrf2 signaling. Keap1 knockdown (Keap1KD) mice that have activated Nrf2 signaling were exposed or not to excess iodide in their drinking water for seven days and compared to respective wild-type mice. RNA-sequencing of individual mouse thyroids identified distinct transcriptomic patterns in response to iodide, with Keap1KD mice showing an attenuated inflammatory response, altered thyroidal autoregulation, and enhanced cell growth/proliferative signaling, as confirmed also by Western blotting for key proteins involved in antioxidant, autoregulatory and proliferative responses. These findings underscore novel gene-environment interactions between the activation status of the Keap1/Nrf2 antioxidant response system and the dietary iodide intake, which may have implications not only for the goiter phenotype of Keap1KD mice but also for humans harboring genetic variations in KEAP1 or NFE2L2 or treated with Nrf2-modulating drugs.

Transcriptome profiling reveals SLC5A5 regulates chicken ovarian follicle granulosa cell proliferation, apoptosis, and steroid hormone synthesis

The egg-laying performance of hens holds significant economic importance within the poultry industry. Broody inheritance of the parent stock of chickens can result in poor options for the improvement of egg production, and is a phenomenon influenced by multiple genetic factors. However, few studies have been conducted to delineate the molecular mechanism of ovarian regression in brooding chickens. Here, we explored the pivotal genes responsible for the regulation of ovarian follicles in laying hens, using RNA-sequencing analysis on the small ovarian follicles from broody and laying chickens. Sequencing data analysis revealed the differential expression of 200 genes, with a predominant enrichment in biological processes related to cell activation and metabolism. Among these genes, we focused on solute carrier family 5 member 5 (SLC5A5), which exhibited markedly higher RNA expression levels in follicles from laying compared with broody chickens. Subsequent cellular function studies with knockdown of SLC5A5 in chicken ovarian follicle granulosa cells (GCs) led to the down-regulation of genes associated with cell proliferation and steroid hormone synthesis, and concurrent promotion of gene expression linked to apoptosis. These findings indicated that SLC5A5 deficiency led to the inhibition of proliferation, steroid hormone synthesis and secretion, and promotion of apoptosis in chicken GCs. Our study demonstrated a pivotal role for SLC5A5 in the development and function of chicken GCs, shedding light on its potential significance in the broader context of chicken ovarian follicle development, and providing a prospective target to improve the egg-laying performance of chickens via molecular marker-assisted breeding technology.

Study on the Relationship Between Serum Iodine and Thyroid Dysfunctions: a Cross-Sectional Study

The relationship between serum iodine (SIC) and thyroid dysfunctions in adults is poorly understood, and this study aimed to explore their relationship. A total of 1320 participants were included in the final analysis. We collected basic demographic information, blood, and spot urine samples to determine serological indices and iodine nutritional status. The median (IQR) of urinary iodine (UIC)/urinary creatinine (UCr), UIC, SIC were 138.1 (91.1, 207.6) μg/g, 155.8 (94.5, 211.1) μg/L, and 70.6 (59.8, 83.9) μg/L, respectively. The 90% reference ranges for UIC/UCr and SIC were 66.5-349.8 mg/g and 49.3-97.1 μg/L. SIC was positively correlated with UIC and UIC/UCr. The prevalence of overt hypothyroidism and subclinical hypothyroidism in female was significantly higher than that in male (P = 0.02, P = 0.002). In male, subjects above the upper reference value of SIC (97.1 μg/L) had a higher risk of subclinical hyperthyroidism (OR = 4.46, 95% CI: 1.29, 12.8) and overt hypothyroidism (OR = 5.59, 95% CI: 1.88, 6.42). In female, subjects below the lower reference value of SIC (49.3 μg/L) had a higher risk of overt hypothyroidism (OR = 2.18, 95% CI: 1.10, 4.06), TgAb positive (OR = 1.97, 95% CI: 1.15, 3.32) and TPOAb positive (OR = 2.48, 95% CI: 1.41, 4.26). In conclusion, serum iodine can be used as an indicator to evaluate iodine nutritional status and thyroid dysfunctions. Higher serum iodine concentration was associated with an increased risk of subclinical hyperthyroidism and overt hypothyroidism in men; lower serum iodine concentration was associated with an increased risk of overt hypothyroidism and positive TgAb and TPOAb in women.

Long-term percutaneous triclosan exposure induces thyroid damage in mice: Interpretation of toxicity mechanism from metabolic and proteomic perspectives

Triclosan (TCS) is an antiseptic incorporated in consumer goods and personal care products that can be absorbed via the skin, raising public health concerns for its continuous detection in human biofluids and tissues. Epidemiology has associated TCS exposure with thyroid function disturbances and decreasing serum thyroid hormone (TH) levels, but the underlying mechanism remains unclear. In this study, we revealed hypothyroidism and histological alternation in the thyroid of mice with chronic percutaneous exposure to TCS, indicating a TCS-caused thyroid impairment. Subsequently, multi-omics approaches were performed to investigate the molecular mechanism of the thyroid in response to long-term dermal TCS exposure. We discovered that TCS interfered with the TH synthesis as indicated by the changes in the levels of the synthetic materials for TH (iodide, Tg, and H2O2) and affected TH release by the downregulation of lysosomal enzymes. The upregulation of glycolysis, tricarboxylic acid cycle, fatty acid, amino acid metabolism, and adenine salvage in the thyroid was also observed after TCS exposure. All these changes led to the elevation of ATP, serving as a rescue for the decreasing thyroid functions. Together, our study demonstrated TCS-induced thyroid damage and identified the interrupted pathways, providing meaningful insight into the molecular mechanisms underpinning the potential health influence of TCS in humans.

Excess iodine exposure acutely increases salivary iodide and antimicrobial hypoiodous acid concentrations in humans

The lactoperoxidase (LPO)-hydrogen peroxide-halides reaction (LPO system) converts iodide and thiocyanate (SCN-) into hypoiodous acid (HOI) and hypothiocyanite (OSCN-), respectively. Since this system has been implicated in defense of the airways and oropharynx from microbial invasion, in this proof-of-concept study we measured the concentrations of these analytes in human saliva from a convenience clinical sample of 40 qualifying subjects before and after acute iodine administration via the iodinated contrast medium used in coronary angiography to test the hypothesis that an iodide load increases salivary iodide and HOI concentrations. Saliva was collected and salivary iodide, SCN-, HOI and OSCN- were measured using standard methodology. The large iodine load delivered by the angiographic dye, several 100-fold in excess of the U.S. Recommended Daily Allowance for iodine (150 µg/day), significantly increased salivary iodide and HOI levels compared with baseline levels, whereas there was no significant change in salivary SCN- and OSCN- levels. Iodine load and changes of salivary iodide and HOI levels were positively correlated, suggesting that higher iodide in the circulation increases iodide output and salivary HOI production. This first of its kind study suggests that a sufficient but safe iodide supplementation less than the Tolerable Upper Limit for iodine set by the U.S. Institute of Medicine (1,100 µg/day) may augment the generation of antimicrobial HOI by the salivary LPO system in concentrations sufficient to at least in theory protect the host against susceptible airborne microbial pathogens, including enveloped viruses such as coronaviruses and influenza viruses.

Thyroidal and Extrathyroidal Requirements for Iodine and Selenium: A Combined Evolutionary and (Patho)Physiological Approach

Iodide is an antioxidant, oxidant and thyroid hormone constituent. Selenoproteins are needed for triiodothyronine synthesis, its deactivation and iodine release. They also protect thyroidal and extrathyroidal tissues from hydrogen peroxide used in the 'peroxidase partner system'. This system produces thyroid hormone and reactive iodine in exocrine glands to kill microbes. Exocrine glands recycle iodine and with high urinary clearance require constant dietary supply, unlike the thyroid. Disbalanced iodine-selenium explains relations between thyroid autoimmune disease (TAD) and cancer of thyroid and exocrine organs, notably stomach, breast, and prostate. Seafood is iodine unconstrained, but selenium constrained. Terrestrial food contains little iodine while selenium ranges from highly deficient to highly toxic. Iodine vs. TAD is U-shaped, but only low selenium relates to TAD. Oxidative stress from low selenium, and infection from disbalanced iodine-selenium, may generate cancer of thyroid and exocrine glands. Traditional Japanese diet resembles our ancient seashore-based diet and relates to aforementioned diseases. Adequate iodine might be in the milligram range but is toxic at low selenium. Optimal selenoprotein-P at 105 µg selenium/day agrees with Japanese intakes. Selenium upper limit may remain at 300-400 µg/day. Seafood combines iodine, selenium and other critical nutrients. It brings us back to the seashore diet that made us what we currently still are.

ESPEN micronutrient guideline

BACKGROUND

Trace elements and vitamins, named together micronutrients (MNs), are essential for human metabolism. Recent research has shown the importance of MNs in common pathologies, with significant deficiencies impacting the outcome.

OBJECTIVE

This guideline aims to provide information for daily clinical nutrition practice regarding assessment of MN status, monitoring, and prescription. It proposes a consensus terminology, since many words are used imprecisely, resulting in confusion. This is particularly true for the words "deficiency", "repletion", "complement", and "supplement".

METHODS

The expert group attempted to apply the 2015 standard operating procedures (SOP) for ESPEN which focuses on disease. However, this approach could not be applied due to the multiple diseases requiring clinical nutrition resulting in one text for each MN, rather than for diseases. An extensive search of the literature was conducted in the databases Medline, PubMed, Cochrane, Google Scholar, and CINAHL. The search focused on physiological data, historical evidence (published before PubMed release in 1996), and observational and/or randomized trials. For each MN, the main functions, optimal analytical methods, impact of inflammation, potential toxicity, and provision during enteral or parenteral nutrition were addressed. The SOP wording was applied for strength of recommendations.

RESULTS

There was a limited number of interventional trials, preventing meta-analysis and leading to a low level of evidence. The recommendations underwent a consensus process, which resulted in a percentage of agreement (%): strong consensus required of >90% of votes. Altogether the guideline proposes sets of recommendations for 26 MNs, resulting in 170 single recommendations. Critical MNs were identified with deficiencies being present in numerous acute and chronic diseases. Monitoring and management strategies are proposed.

CONCLUSION

This guideline should enable addressing suboptimal and deficient status of a bundle of MNs in at-risk diseases. In particular, it offers practical advice on MN provision and monitoring during nutritional support.

Is the urinary iodine/creatinine ratio applicable to assess short term individual iodine status in Chinese adults? Comparison of iodine estimates from 24-h urine and timed-spot urine samples in different periods of the day

Background

Urinary iodine concentration (UIC) is routinely used to evaluate the population iodine status while the uniform method for the individual level assessment is uncertain.

Objectives

To explore the 24-h urinary iodine excretion (UIE) in five different periods of the day and the corresponding prediction equations respect by the use of creatinine-corrected UIC.

Methods

We collected 24-h, spot and fasting urine in five periods of the day to estimate 24-h UIE by the six different prediction equations. We compared the estimated creatinine-corrected UIC to the collected 24-h UIE and identified the most suitable equations in each period of the day.

Results

Among the six different prediction equations, the equation of Kawasaki T was the best to estimate the 24-h UIE by fasting urine among Chinese adults. Among the five periods of time, the equation of Knudsen N was the best to estimate the 24-h UIE in the non-morning period.

Conclusion

Urinary iodine status at the individual level could be estimated by different creatinine-based equations at different periods of the day.

Radioiodine Imaging and Treatment in Thyroid Disorders

Thyroid hormones T3 and T4 are crucial for development and differentiation of various cells in the body. They are also essential for regulating metabolism in nearly all tissues. Iodine is an integral element in the synthesis of thyroid hormone and is actively transported into the thyroid by a Na⁺/I^- symporter. The thyroid can take up radioactive iodine just like it would take iodine and hence can be used to evaluate and treat several thyroid diseases. Radioactive iodine is one of the first radioisotopes to be used in medicine.

Magnitude and associated factors of menstrual irregularity among undergraduate students of Debre Berhan University, Ethiopia

Background

Menstrual irregularity is a common problem among women aged from 21 to 25years. Previously published work on menstrual irregularity used inconsistent definition which results in a difference in prevalence. Therefore the study aimed to assess the magnitude and associated factors of menstrual irregularity among undergraduate students of Debre Berhan University, Ethiopia.

Methods

A cross-sectional study design was carried out among 660 undergraduate female students at Debre Berhan University. To get representative study participants, a stratified sampling technique was used. To collect the data self-administered questionnaire was used. Physical examination and anthropometric measurement were also done. Data were analyzed by using SPSS version 21. Logistic regression analysiswas done. A significant association was declared at a p-value less than 0.05.

Result

A total of 620 students participated in the present study with a response rate of 93.9%. Out of the total study participants, 32.6% (95% CI 2936.5) participants had irregular menstrual cycle. Significant association was found between anemia (AOR=2.1; 95%CI 1.3373.441), alcohol intake (AOR=2.4; 95%CI 1.254.666),<5 sleep hours (AOR=5.4; 95%CI 2.9759.888), 67 sleep hours (AOR=1.9; 95%CI 1.2912.907), Perceived stress (AOR=3.3; 95%CI 1.83225.940), iodine deficiency disorder (IDD) (AOR=3.9; 95%CI 1.32511.636) and underweight (AOR=1.8; 95%CI 1.1092.847) with menstrual irregularity.

Conclusion

The finding of this study reported a low magnitude of menstrual irregularity as compared to previous studies. Students should adopt healthier lifestyle practices (weight control, stress control, anemia control, and avoid alcohol intake) to control menstrual irregularity.

Menstrual irregularity is a common problem among university students. It affects their daily activities. But it lacks attention, especially in developing countries. Additionally, menstrual irregularity is defined differently by different researchers which results in a difference in prevalence. So it is difficult to compare. Therefore this study aims to assess the magnitude and associated factors of menstrual irregularity among undergraduate students of Debre Berhan University, Ethiopia. To avoid the inconsistent definition of menstrual irregularity which is used by different researchers, we used the standard of menstrual irregularity definition which was prepared by the international federation of obstetrics and gynecologist in 2018.

This study uses across sectional study design among 660 undergraduate students of Debre Berhan University, Ethiopia. A self-administered questioner which includes socio-demographic data, menstrual-related questions, lifestyle and behavioral questions, and medical history questions were used to collect data. Besides, physical examination and anthropometric measurement were done.

Of a total 620 students who participated in the study: 202 (32.6%) had menstrual irregularity. Factors that had significant association with menstrual irregularity were, anemia (AOR=2.1; 95%CI 1.3373.441), alcohol intake (AOR=2.4; 95%CI 1.254.666),<5 sleep hours (AOR=5.4; 95%CI 2.9759.888), 67 sleep hours (AOR=1.9; 95%CI 1.2912.907), Perceived stress (AOR=3.3; 95%CI 1.83225.940), iodine deficiency disorder (IDD) (AOR=3.9; 95%CI 1.32511.636) and underweight (AOR=1.8; 95%CI 1.1092.847). In conclusion, the finding of this study reported a low magnitude of menstrual irregularity as compared to previous studies.

The Keap1/Nrf2 Signaling Pathway in the Thyroid-2020 Update

The thyroid gland has a special relationship with oxidative stress. On the one hand, like all other tissues, it must defend itself against reactive oxygen species (ROS). On the other hand, unlike most other tissues, it must also produce reactive oxygen species in order to synthesize its hormones that contribute to the homeostasis of other tissues. The thyroid must therefore also rely on antioxidant defense systems to maintain its own homeostasis in the face of continuous self-exposure to ROS. One of the main endogenous antioxidant systems is the pathway centered on the transcription factor Nuclear factor erythroid 2-related factor 2 (Nrf2) and its cytoplasmic inhibitor Kelch-like ECH-associated protein 1 (Keap1). Over the last few years, multiple links have emerged between the Keap1/Nrf2 pathway and thyroid physiology, as well as various thyroid pathologies, including autoimmunity, goiter, hypothyroidism, hyperthyroidism, and cancer. In the present mini-review, we summarize recent studies shedding new light into the roles of Keap1/Nrf2 signaling in the thyroid.

High prevalence of TPO-Abs and subclinical hypothyroidism in iodine-sufficient pregnant women in Northern Algeria

BACKGROUND

Iodine is a trace element whose adequate intakes are essential during gestation to promote the correct growth and development of the fetus. Historically, endemic goiter and cretinism affected northern regions of Algeria, and iodized salt was introduced in 1990. However, there has been no national study of iodine nutrition in Algeria since 1994. The aim of this study was to assess the iodine status and thyroid function of women of reproductive age (WRA) and pregnant women (PW) in northern Algeria.

METHODS

Healthy WRA and PW were recruited from an urban area (Algiers) and healthy WRA from a rural area (Tizi-Ouzou). Spot urine and venous blood samples were collected to assess iodine status (urinary iodine concentration, UIC) and serum thyroid hormones (TSH, FT4), thyroglobulin (Tg), and anti-thyroid peroxidase antibodies (TPO-Ab) concentrations.

RESULTS

The median UIC in WRA was 256 μg/L (IQR: 166-354 μg/L; n = 151) in Algiers and 253 μg/L (167-341 μg/L; n = 150) in Tizi-Ouzou. The median UIC for the PW in Algiers was 233 μg/L (IQR: 157-326 μg/L; n = 173).Thirty-five percent of WRA and 30% of PW had an UIC > 300 μg/L. Median TSH, FT4 and Tg concentrations were within reference ranges in all groups of women. Among PW, 72.7%, 75.4% and 75.5% in the first, second and third trimester were TPO-Ab+. Among TPO-Ab + PW in the first, second and third trimesters, 18.7%, 13% and 10.3% had subclinical hypothyroidism.

CONCLUSION

In northern Algeria, median UICs in PW indicate iodine sufficiency, and in WRA indicate more than adequate intakes. About 75% of PW are TPO-Ab + and the prevalence of subclinical hypothyroidism is high. Monitoring and surveillance of iodine fortification programs is vital to avoid both iodine deficiency and excess. There is an urgent need for a comprehensive national iodine status survey including school-age children and other vulnerable population groups in Algeria.

Selenium and iodine in diabetes mellitus with a focus on the interplay and speciation of the elements

Diabetes mellitus is a chronic metabolic disease caused by insulin deficiency (type I) or dysfunction (type II). Diabetes is a threatening public health concern. It is considered as one of the priority non-communicable diseases, due to its high and increasing incidence, the associated healthcare costs, and threatening medical complications. Two trace elements selenium (Se) and iodine (I) were intensively discussed in the context of diabetic pathology and, possibly, etiology. It seems there is a multilayer involvement of these essential nutrients in glucose tolerance, energy metabolism, insulin signaling and resistance, which are mainly related to the antioxidant selenoenzymes and the thyroid hormones. Other factors might be related to (auto)immunity, protection against endoplasmic reticulum stress, and leptin signaling. The aim of the current review is to evaluate the current understanding of the role of selenium and iodine in diabetes with a focus on the biochemical interplay between the elements, their possible role as biomarkers, and their chemical speciation. Possible impacts from novel analytical techniques related to trace element speciation and isotopic analysis are outlined.

Investigation into the Biological Impact of Block Size on Cathepsin S-Degradable HPMA Copolymers

N-(2-Hydroxypropyl)methacrylamide (HPMA) copolymers have been studied as an efficient carrier for drug delivery and tumor imaging. However, as with many macromolecular platforms, the substantial accumulation of HPMA copolymer by the mononuclear phagocyte system (MPS)-associated tissues, such as the blood, liver, and spleen, has inhibited its clinical translation. Our laboratory is pursuing approaches to improve the diagnostic and radiotherapeutic effectiveness of HPMA copolymers by reducing the nontarget accumulation. Specifically, we have been investigating the use of a cathepsin S (Cat S)-cleavable peptidic linkers to degrade multiblock HPMA copolymers to increase MPS-associated tissue clearance. In this study, we further our investigation into this area by exploring the impact of copolymer block size on the biological performance of Cat S-degradable HPMA copolymers. Using a variety of in vitro and in vivo techniques, including dual labeling of the copolymer and peptide components, we investigated the constructs using HPAC pancreatic ductal adenocarcinoma models. The smaller copolymer block size (S-CMP) demonstrated significantly faster Cat S cleavage kinetics relative to the larger system (L-CMP). Confocal microscopy demonstrated that both constructs could be much more efficiently internalized by human monocyte-differentiated macrophage (hMDM) compared to HPAC cells. In the biodistribution studies, the multiblock copolymers with a smaller block size exhibited faster clearance and lower nontarget retention while still achieving good tumor targeting and retention. Based on the radioisotopic ratios, fragmentation and clearance of the copolymer constructs were higher in the liver compared to the spleen and tumor. Overall, these results indicate that block size plays an important role in the biological performance of Cat S-degradable polymeric constructs.