Age-related variation in thyroid function - a narrative review highlighting important implications for research and clinical practice

IGFBP5 protein molecule and thyroid hormone in the diagnosis and effect of gestational diabetes

Gestational diabetes mellitus (GDM) is an abnormal state of glucose metabolism that first appears during pregnancy and poses a serious threat to maternal and infant health. In recent years, with the change of lifestyle and the update of diagnostic criteria, the incidence of GDM has increased year by year. Blood samples from pregnant women diagnosed with gestational diabetes were collected, concentrations of IGFBP5 protein molecules were measured by enzyme-linked immunosorbent assay (ELISA), and thyroid stimulating hormone (TSH) levels were measured by radioimmunoassay. Relevant clinical data were collected to exclude other variables that might affect the results. Correlation analysis showed that IGFBP5 protein concentration was negatively correlated with blood glucose level, but positively correlated with TSH level. Multiple regression analysis further revealed that IGFBP5 protein molecules and TSH levels are important factors affecting the development of gestational diabetes mellitus. This study confirms the diagnostic potential of the IGFBP5 protein molecule in gestational diabetes and reveals the complex effects of its interaction with thyroid stimulating hormone on glucose metabolism. The decrease of IGFBP5 protein concentration and thyroid stimulating hormone level may be the markers of the development of GDM. Therefore, the detection of IGFBP5 protein molecules and thyroid stimulating hormone levels is expected to provide new ideas and methods for the early diagnosis and treatment of GDM.

The association of thyroid hormone levels and incidence of chronic kidney disease: the Tehran thyroid study (TTS)

BACKGROUND

Evidence regarding the relationship between thyroid hormone levels within the normal range and the incidence of chronic kidney disease (CKD) in adults is scarce. This study aimed to identify the association between thyrotropin (TSH) and free thyroxine (FT4) levels with the incidence of CKD in a large cohort study over long-term follow-up.

METHODS

This prospective cohort study, with an 18-year follow-up, included 4118 adults without CKD from the Tehran thyroid Study (TTS). Participants were categorized by tertiles of normal TSH levels (low-normal, middle-normal, and high-normal) and abnormal TSH. The study outcome was incident CKD, defined as an estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m2. Multivariable Cox proportional hazard models were used to estimate hazard ratios (HRs) for CKD incidence based on thyroid hormone levels.

RESULTS

The HR for CKD development was 1.08 (95%CI: 1.01-1.15) per 1 SD increase in the TSH levels. Compared with participants with low-normal TSH levels, those with high-normal (HR:1.37; 95%CI: 1.03-1.84) and abnormal TSH (HR:1.24; 95%CI: 1.05-1.46) had a significantly higher risk of developing CKD. In subgroup analyses, the association between TSH level and CKD was significant in participants younger than 60 years, females, non-obese, non-smokers, and those without diabetes and hypertension. No association was observed between FT4 levels and incident CKD (HR: 0.92; 95%CI: 0.79-1.09). However, a significant association was observed between FT4 levels within the normal range and CKD development in those younger than 60 years old (HR: 0.77; 95% CI: 0.61-0.98).

CONCLUSION

Increased TSH levels, even within the normal range, linearly increased the risk of CKD even after adjustment for important risk factors. As a result, TSH may potentially be an independent risk factor for incident CKD.

Serum Klotho protein level in patients with thyroid dysfunction

OBJECTIVES

This study focused on determining the new marker Klotho and its correlation with other parameters in thyroid dysfunction.

METHODS

Seventy-seven thyroid dysfunction patients were recruited during the period (from Aug 2024 to Dec 2024) with an age range (33-56) years. The patient group was subdivided into two groups: group I (21) Patients with Hyperthyroidism and group II (56) Patients with Hypothyroidism, for comparison, 30 healthy individuals were included as a control. The protein level Klotho was estimated using ELISA. Biochemical parameters; blood urea, creatinine, and lipid profile were measured spectrophotometrically. T3, T4 and TSH were determined using ELFA kit.

RESULTS

Serum levels of Klotho protein were significantly lower (p-value < 0.001) in group I compared to the control group. There was a significant difference (p < 0.001) in the Klotho protein levels in group II compared with the control group. Klotho protein was negatively correlated to TSH, creatinine concentrations, and age. The AUC was excellent with high diagnostic accuracy in differentiating newly diagnosed thyroid dysfunction from the healthy subject group.

CONCLUSIONS

Serum Klotho levels in patients with thyroid dysfunction significantly decreased, particularly in hypothyroidism patients. These levels are inversely correlated with thyroid-stimulating hormone levels and age.

Women-specific reference ranges for serum TSH in Liguria: the impact of age and year of collection in a single-center cross-sectional study

BACKGROUND

TSH is the first-line test of thyroid function, and the normal TSH references provided by manufacturers are generally used in diagnoses. In the age of gender medicine, however, there is a need to refine normal TSH ranges.

AIM

The aim of this study was to construct a normal TSH range in women living in our district. The data were collected in a secondary-level centre located in Savona (Liguria, Italy).

METHODS

From 2003 to 2022, 6227 medical records from women undergoing their first endocrinological examination were anonymously evaluated. After the application of exclusion criteria, statistical analysis was anonymously performed on a sample of 2597 medical records.

RESULTS

The pooled median 2.5th and 97.5th percentiles of TSH provided by manufacturers were 0.20 mIU/l and 5.64 mIU/l, respectively. In the study population, median (2.5th - 97.5th percentiles) TSH was 1.70 mIU/l (0.37-6.95 mIU/l). TSH and patient age did not vary significantly over the years (2003-2022). A slight negative correlation was found between TSH and age (P = 0.05). On stratifying the sample into three age-groups (18-44 years, N = 1200; 45-64 years N = 934; ≥65 years, N = 463), TSH was 1.75 mIU/l (0.49-5.94 mIU/l), 1.70 mIU/l (0.30-6.89 mIU/l) and 1.64 mIU/l (0.30-7.69 mIU/l), respectively. When TSH was evaluated according to the age-related range instead of the pooled range reported by manufacturers, the number of women aged 18-44 years considered to have sub-clinical hyperthyroidism increased slightly (P = 0.02) and the number of women in the 45-64-year and ≥ 65-year age-groups considered to have sub-clinical hypothyroidism decreased significantly (P = 0.05 and P < 0.001).

CONCLUSIONS

This is the first study in Liguria aimed at establishing new age-specific reference values for TSH in women. Based on a large number of data, this new age-related range could be more extensively employed in order to improve diagnosis. The main result of implementing age-related normal TSH levels between the 2.5th and 97.5th percentiles seems to be both a slight increase in 18-44-year-old women and a significant reduction in > 45-year-old women in whom sub-clinical hyperthyroidism or hypothyroidism, respectively, should be promptly treated.

Healthy Aging Metabolomic and Proteomic Signatures Across Multiple Physiological Compartments

The study of biomarkers in biofluids and tissues expanded our understanding of the biological processes that drive physiological and functional manifestations of aging. However, most of these studies were limited to examining one biological compartment, an approach that fails to recognize that aging pervasively affects the whole body. The simultaneous modeling of hundreds of metabolites and proteins across multiple compartments may provide a more detailed picture of healthy aging and point to differences between chronological and biological aging. Herein, we report proteomic analyses of plasma and urine collected in healthy men and women, age 22-92 years. Using these data, we developed a series of metabolomic and proteomic predictors of chronological age for plasma, urine, and skeletal muscle. We then defined a biological aging score, which measures the departure between an individual's predicted age and the expected predicted age for that individual based on the full cohort. We show that these predictors are significantly and independently related to clinical phenotypes important for aging, such as inflammation, iron deficiency anemia, muscle mass, and renal and hepatic functions. Despite a different set of selected biomarkers in each compartment, the different scores reflect a similar degree of deviation from healthy aging in single individuals, thus allowing identification of subjects with significant accelerated or decelerated biological aging.

Molecular Mechanisms of Vascular Tone in Exercising Pediatric Populations: A Comprehensive Overview on Endothelial, Antioxidative, Metabolic and Lipoprotein Signaling Molecules

Vasoactive molecules are central regulators of vascular tone, angiogenesis and inflammation. Key molecular agents include nitric oxide (NO), endothelin-1 (ET-1), prostacyclin, free triiodothyronine (fT3), leptin, low-density lipoprotein (LDL), high-density lipoprotein (HDL), superoxide dismutase (SOD), and glutathione peroxidase (GPX). Dysregulation of these compounds can lead to endothelial dysfunction, an early predictor of atherosclerosis and cardiovascular diseases (CVD). Maintaining endothelial health is thus essential for vascular homeostasis and cardiovascular risk prevention. Regular exercise serves as a vital protective measure against CVD and the risk of cardiovascular conditions. However, young athletes often significantly exceed recommended levels of training load, engaging in highly intensive training that leads to substantial physiological adaptations. Despite this, research on the impact of exercise on vasoactive substances in children and adolescents, particularly young athletes, is limited and inconsistent. Most studies focus on those with pre-existing conditions, like obesity or diabetes mellitus. Existing findings suggest exercise may favorably affect vascular biomarkers in youth, but methodological variations hinder consistent conclusions. This literature review examines 68 studies on the effects of exercise on vascular molecules in children and adolescents, young athletes, and children and adolescents with pre-existing conditions, offering deeper insights into how exercise may influence vascular health at the molecular level.

Thyroid Dysfunction Prevalence and Risk Factors in the Southeastern Part of Bangladesh: A Cross-Sectional Study

Background and Aims

Globally thyroid disorders (TDs) are common health issues including in the Southeast Asian region. The purpose of this study was to ascertain the prevalence of thyroid disorders in the Bangladeshi population, with a particular focus on the frequency, etiology, and comorbidity of various thyroid diseases.

Methods

A cross-sectional research design was conducted in the southeastern part of Bangladesh. Information regarding prior diagnosis and current management of TDs was obtained through a questionnaire.

Results

Of the 300 respondents, 209 were female, and 91 were male. Females were found to be more predominant across all categories of TDs (χ 2 = 17.738, p < 0.05). Furthermore, the older age group (31-45 years) demonstrated a higher frequency of thyroid problems (OR: 1.320). Specifically, hyperthyroidism was identified as the most common thyroid disorder, followed by hypothyroidism, and euthyroidism. Hyperthyroidism was found to be less common in males (18.69%) compared to females (43.06%), while hypothyroidism was more prevalent in males (46.15%) compared to females (27.75%). Multiple logistic regression analysis demonstrates that participants with a family history of TDs have a significantly higher chance (OR: 2.991, CI: 1.480-6.044, p < 0.05) of having hyperthyroidism than those without such a history. Interestingly, the studied population also exhibited higher rates of comorbidities including gastritis, diabetes, and cardiovascular diseases.

Conclusion

According to the study's findings, it is advised to concentrate on educating Bangladeshis about thyroid problems, particularly female population. Moreover, healthcare professionals should check elderly patient's thyroid conditions and consider the possibility that thyroid dysfunction can coexist with other conditions.

Changes in thyroid function and autoimmunity in older individuals: longitudinal analysis of the Whickham cohort

BACKGROUND

Longitudinal studies of thyroid function have demonstrated differing results. It remains unclear whether changes in thyroid function affect the diagnosis of subclinical thyroid dysfunction with ageing.

METHODS

Survivors of the Whickham cohort study were evaluated on two occasions between the years 2008-2012 and 2016-2019. Serum thyrotropin (TSH), free thyroxine (FT4), free triiodothyronine (FT3) and thyroid peroxidase antibody (TPOAb) were measured on both occasions using the same assay under similar conditions. Individuals with known thyroid disease or on medications affecting thyroid function were excluded. Comorbidities were noted, functional mobility was assessed by the timed up-and-go test and muscle function was evaluated by the hand grip strength test.

RESULTS

In 204 individuals (mean age 77.0 [±6.6] years, 114 [56%] female), followed over a median (IQR) of 7.8 (7.3-8.2) years, serum TSH increased by 0.29 mU/L (12.4%), FT3 and TPOAb reduced by 0.1 pmol/L (-2.1%) and 0.6 U/L (-11.2%) and there were no significant changes in FT4 levels. The calculated upper limit of serum TSH increased over the follow-up period from 4.74 mU/L to 6.28 mU/L. The relationship between serum TSH and FT4 at both time points were not significantly different. Utilising standard laboratory reference ranges, the prevalence of subclinical hypothyroidism increased from 3.5% at baseline to 9.0% at follow-up. However, adopting a visit-specific TSH reference range reduced the prevalence of subclinical hypothyroidism at both time points to 2.0%.

DISCUSSION

Thyroid function demonstrates subtle but significant changes with age. Utilising standard reference ranges tends to increase the diagnosis of subclinical hypothyroidism in older euthyroid individuals. Our data suggest that adopting age-appropriate TSH reference ranges may reduce the risk of diagnosing and (potentially unnecessarily) treating subclinical hypothyroidism.

Thyroid scintigraphy: establishing a clinically useful normal range for 99mTc pertechnetate uptake

PURPOSE

This study aims to establish a normal range for the thyroid uptake derived from 99mTc pertechnetate scans. In particular, variations of uptake with TSH stimulation and other factors such as urinary iodine concentration are taken into account and compared with the calculation of a raw uptake value.

METHODS

Clinical multicentric (center A, B and C) prospective study on 125 consecutive healthy patients undergoing thyroid scans for thyroid nodules. Normal functional thyroid status was assured by normal TSH, normal thyroid size, no thyroid antibodies and no symptoms of thyroid functional disorders. Calculations of raw Tc-uptake (uptake) and modified uptake values regarding current TSH value (uptakeTSH1), urinary iodine concentration (uptakeTSH1&uic), gland volume, age, smoking status, weight and tissue thickness ventral to the thyroid were performed.

RESULTS

There is a positive correlation of thyroid uptake with TSH allowing for the calculation of a normalized uptake value (uptakeTSH1). The normal range for uptakeTSH1 compares favourable to that for raw uptake in that it yields a clear distinction from thyroid functional disorders. The additional normalization for urinary iodine concentration (uptakeTSH1&uic) may even improve the distinctive power whereas further normalizations such as for gland volume, age and others are not warranted by this study. The 95% CI of uptakeTSH1 for sites A, A&B, and A&B&C were 0.21%-2.06%, 0.22%-2.38% and 0.24%-2.40%.

CONCLUSION

A normal range for the thyroid uptake can be established with respect to the current TSH stimulation. This normalization (uptakeTSH1) overcomes the drawback of raw uptake by yielding a clinically useful parameter with obviously high distinctive power against functional thyroid disorders.

Mechanisms of muscle cells alterations and regeneration decline during aging

Skeletal muscles are essential for locomotion and body metabolism regulation. As muscles age, they lose strength, elasticity, and metabolic capability, leading to ineffective motion and metabolic derangement. Both cellular and extracellular alterations significantly influence muscle aging. Satellite cells (SCs), the primary muscle stem cells responsible for muscle regeneration, become exhausted, resulting in diminished population and functionality during aging. This decline in SC function impairs intercellular interactions as well as extracellular matrix production, further hindering muscle regeneration. Other muscle-resident cells, such as fibro-adipogenic progenitors (FAPs), pericytes, and immune cells, also deteriorate with age, reducing local growth factor activities and responsiveness to stress or injury. Systemic signaling, including hormonal changes, contributes to muscle cellular catabolism and disrupts muscle homeostasis. Collectively, these cellular and environmental components interact, disrupting muscle homeostasis and regeneration in advancing age. Understanding these complex interactions offers insights into potential regenerative strategies to mitigate age-related muscle degeneration.

Hypothyroidism

Hypothyroidism, the deficiency of thyroid hormone, is a common condition worldwide. It affects almost all body systems and has a wide variety of clinical presentations from being asymptomatic to, in rare cases, life threatening. The classic symptoms of hypothyroidism include fatigue, lethargy, weight gain, and cold intolerance; however, these symptoms are non-specific and the diagnosis is typically made on biochemical grounds through serum thyroid function tests. The most common cause of hypothyroidism is chronic autoimmune thyroiditis (Hashimoto's thyroiditis), although other causes, including drugs (such as amiodarone, lithium, and immune checkpoint inhibitors), radioactive-iodine treatment, and thyroid surgery, are frequent. Historically, severe iodine deficiency was the most common cause. Reference ranges for thyroid function tests are based on fixed percentiles of the population distribution, but there is increasing awareness of the need for more individualised reference intervals based on key factors such as age, sex, and special circumstances such as pregnancy. Levothyroxine monotherapy is the standard treatment for hypothyroidism; it is safe and inexpensive, restores thyroid function tests to within the reference range, and improves symptoms in the majority of patients. However, 10% of patients have persistent symptoms of ill health despite normalisation of thyroid function tests biochemically and a substantial proportion of patients on levothyroxine have thyroid-stimulating hormone concentrations outside the reference range. Ongoing symptoms despite levothyroxine treatment has led to some patients using liothyronine or desiccated thyroid extract. Taken together, these factors have led to intense debate around the treatment thresholds and treatment strategies for hypothyroidism. In this Seminar, we review the epidemiology, genetic determinants, causes, and presentation of hypothyroidism; highlight key considerations and controversies in its diagnosis and management; and provide future directions for research.

The impact of the SARS-CoV2 pandemic on the prescription of thyroid medication in Austria - A nationwide population-based registry analysis

BACKGROUND

Case reports indicate a clinical connection between SARS-CoV-2 and thyroid dysfunctions. However, evidence from large population-based registry analyses is sparse, especially in Europe, where iodine deficiency is common. This study aimed to analyze the impact of the COVID-19 pandemic on healthcare provision for thyroid diseases in Austria.

METHODS

We performed a retrospective, population-based registry analysis of the Austrian health insurance fund database, covering more than 9 million inhabitants. Data from all patients with prescriptions of thyroid-specific drugs and/or inpatient thyroid-related diagnoses from 2017 to 2019 (pre-pandemic years) were compared to 2020 and 2021 (pandemic years; characterized by high numbers of SARS-CoV2 infections and population-wide vaccination strategy). The incidence rates of thyroid medication prescriptions for hypothyroidism and hyperthyroidism were calculated for every year to evaluate the impact of the pandemic.

RESULTS

The incidence rate for total thyroid medication prescription was 539.07/100,000 individuals (534.23-543.93 95%CI) in 2018 and declined during the pandemic (2020: 387.19/100,000 (383.12-391.29 95%CI); 2021: 336.90/100,000 (333.11-340.73 95%CI)). Similarly, the incidence rate for levothyroxine prescription was higher pre-pandemic (2018: 465.46/100,000 (460.97-469.98 95%CI) and declined during the pandemic (2020: 348.14/100,000 (344.28-352.03 95%CI); 2021: 300.30/100,000 (296.7-303.91 95%CI). The incidence rates of thiamazole prescriptions (2018: 10.24/100,000 (9.58-10.93 95%CI); 2020: 8.62/100,000 (8.03-9.26 95%CI); 2021: 11.17/100,000 (10.49-11.89 95%CI) were stable.

CONCLUSIONS

These findings suggest no clinically significant impact of SARS-CoV2 and/or vaccination on thyroid function at a population level.

Risks of suboptimal and excessive thyroid hormone replacement across ages

BACKGROUND

Hypothyroidism is prevalent at all ages and represents a non-communicable disease with preventable consequences.

METHOD

Narrative review.

REVIEW

In children and adolescents, the most devastating consequences of undertreatment with levothyroxine (LT4) are poor growth and development. Delayed treatment in congenital hypothyroidism can lead to permanent brain damage. In young to middle-aged adults, symptoms are often overlooked, and treatment delayed by many years. The resulting consequences are also at this age group compromised brain and physical function but less severe and partly reversible with treatment. The under-treated condition often results in a higher risk of, e.g., increased cardiovascular disease burden, obesity, hypertension, poor physical capacity, and poor quality of life. Excessive replacement is at all adult age groups associated with increased risk of cardiac death, osteoporosis, loss of muscle function, psychological instability and poor quality of life. In young fertile women, the consequences of undertreatment with LT4 are subnormal fertility, recurrent pregnancy loss, compromised fetal growth, and neurocognitive development. On the other hand, excessive LT4 treatment has been related to gestational hypertension, preeclampsia and preterm birth. In the elderly, care must be given to avoid confusing a slightly high age-related serum TSH with requirement for LT4 treatment in a truly hypothyroid patient. Excessive LT4 treatment in patients of high age is associated with an increased mortality.

CONCLUSION

Suboptimal and excessive LT4 replacement of the preventable non-communicable disease hypothyroidism requires more focus from the healthcare system and from the global political systems to prevent the personally devastating and socioeconomically challenging consequences.

Consequences of undertreatment of hypothyroidism

PURPOSE

To provide an overview of consequences of undertreatment with levothyroxine (LT4) in the common non-communicable disease, hypothyroidism.

METHODS

Narrative review of the literature.

RESULTS

Hypothyroidism is globally very prevalent at all age groups and represents a non-communicable disease in which the risks and consequences are preventable. In children and adolescents, the most devastating consequences of undertreatment are poor growth and development. Lack of early treatment in congenital hypothyroidism can lead to permanent damage of brain function. In young to middle-aged adults, consequences are often overlooked, and treatment delayed by many years. The resulting consequences are also at this age group compromised brain and physical functioning but less severe and partly reversible with treatment. The undertreated condition often results in a higher risk of several secondary devastating diseases such as increased cardiovascular disease burden, obesity, hypertension, poor physical capacity, poor quality of life. In young women of fertile age the consequences of undertreatment with LT4 are subnormal fertility, recurrent pregnancy loss, preeclampsia, compromised fetal growth and neurocognitive development. There is a further risk of 30-50% of developing postpartum thyroiditis. In the elderly population care must be given to avoid confusing a slightly high serum TSH as result of physiological age adaptation with a requirement for LT4 treatment in a truly hypothyroid patient.

CONCLUSION

Undertreatment of the preventable non-communicable disease hypothyroidism requires more focus both from caretakers in the healthcare system, but also from the global political systems in order to prevent the personally devastating and socioeconomically challenging consequences.

Phase 2 Trial Evaluating Minocycline for Geographic Atrophy in Age-Related Macular Degeneration: A Nonrandomized Controlled Trial

Importance

Existing therapies to slow geographic atrophy (GA) enlargement in age-related macular degeneration (AMD) have relatively modest anatomic efficacy, require intravitreal administration, and increase the risk of neovascular AMD. Additional therapeutic approaches are desirable.

Objective

To evaluate the safety and possible anatomic efficacy of oral minocycline, a microglial inhibitor, for the treatment of GA in AMD.

Design, Setting, and Participants

This was a phase 2, prospective, single-arm, 45-month, nonrandomized controlled trial conducted from December 2016 to April 2023. Patients with GA from AMD in 1 or both eyes were recruited from the National Institutes of Health (Bethesda, Maryland) and Bristol Eye Hospital (Bristol, UK). Study data were analyzed from September 2022 to May 2023.

Intervention

After a 9-month run-in phase, participants began oral minocycline, 100 mg, twice daily for 3 years.

Main Outcomes and Measures

The primary outcome measure was the difference in rate of change of square root GA area on fundus autofluorescence between the 24-month treatment phase and 9-month run-in phase.

Results

Of the 37 participants enrolled (mean [SD] age, 74.3 [7.6] years; 21 female [57%]), 36 initiated the treatment phase. Of these participants, 21 (58%) completed at least 33 months, whereas 15 discontinued treatment (8 by request, 6 for adverse events/illness, and 1 death). Mean (SE) square root GA enlargement rate in study eyes was 0.31 (0.03) mm per year during the run-in phase and 0.28 (0.02) mm per year during the treatment phase. The primary outcome measure of mean (SE) difference in enlargement rates between the 2 phases was -0.03 (0.03) mm per year (P = .39). Similarly, secondary outcome measures of GA enlargement rate showed no differences between the 2 phases. The secondary outcome measures of mean difference in rate of change between 2 phases were 0.2 letter score per month (95% CI, -0.4 to 0.9; P = .44) for visual acuity and 0.7 μm per month (-0.4 to 1.8; P = .20) for subfoveal retinal thickness. Of the 129 treatment-emergent adverse events among 32 participants, 49 (38%) were related to minocycline (with no severe or ocular events), including elevated thyrotropin level (15 participants) and skin hyperpigmentation/discoloration (8 participants).

Conclusions and Relevance

In this phase 2 nonrandomized controlled trial, oral minocycline was not associated with a decrease in GA enlargement over 24 months, compared with the run-in phase. This observation was consistent across primary and secondary outcome measures. Oral minocycline at this dose is likely not associated with slower rate of enlargement of GA in AMD.

Impact of non-severe infections on cortisol and thyroid stimulating hormone baseline levels in hospitalized patients: A monocentric cross-sectional study

Objective. The hormonal balance is dependent on the internal and external stimuli. The baseline cortisol (BC) and thyroid stimulating hormone (TSH) levels have been observed to vary and have a predictive value in critical illness settings. Few reports have studied their variation in non-severe acute illness. The present study aims to describe the variation of BC and TSH levels and to determine the factors influencing BC and TSH levels in patients admitted with non-severe acute illness. Patients and Methods. This is a cross-sectional study of patients admitted to Infectious Diseases and Endocrinology units at the Department of Endocrinology-Diabetology and Internal Medicine at Tahar Sfar University Hospital between March 15th and September 15th, 2020. BC and TSH levels were obtained during the hospitalization. Results. A total of 143 patients were included in this study with 75 presenting with infection. All infections were community-acquired and predominantly non-severe. The BC levels were higher in patients with infection (p=0.004), especially those admitted via the emergency department (p=0.009) with a fever (p=0.015). The BC positively correlated with the temperature (p=0.002, r'=0.350), CRP levels (p=0.002, r'=0.355), neutrophil to lymphocyte ratio (p=0.045, r'=0.235), and SOFA score (p=0.023, r'=0.262). On the other hand, TSH levels were comparable in the presence of infection (p=0.400). TSH levels did not correlate with the fever, the severity of infection, or inflammation biomarkers. Both BC and TSH did not predict unfavorable outcomes in non-severe infected patients. Conclusion. In patients admitted with critical acute infections, the BC levels seem to indicate a relatively more severe infectious state. On the other hand, TSH levels did not show significant variations in these patients.

The ageing thyroid: implications for longevity and patient care

Thyroid hormones have vital roles in development, growth and energy metabolism. Within the past two decades, disturbances in thyroid hormone action have been implicated in ageing and the development of age-related diseases. This Review will consider results from biomedical studies that have identified the importance of precise temporospatial regulation of thyroid hormone action for local tissue maintenance and repair. Age-related disturbances in the maintenance of tissue homeostasis are thought to be important drivers of age-related disease. In most iodine-proficient human populations without thyroid disease, the mean, median and 97.5 centile for circulating concentrations of thyroid-stimulating hormone are progressively higher in adults over 80 years of age compared with middle-aged (50-59 years) and younger (20-29 years) adults. This trend has been shown to extend into advanced ages (over 100 years). Here, potential causes and consequences of the altered thyroid status observed in old age and its association with longevity will be discussed. In about 5-20% of adults at least 65 years of age, thyroid-stimulating hormone concentrations are elevated but circulating concentrations of thyroid hormone are within the population reference range, a condition referred to as subclinical hypothyroidism. Results from randomized clinical trials that have tested the clinical benefit of thyroid hormone replacement therapy in older adults with mild subclinical hypothyroidism will be discussed, as well as the implications of these findings for screening and treatment of subclinical hypothyroidism in older adults.

Association between shift work and the risk of hypothyroidism in adult male workers in Korea: a cohort study

Background

Shift work has been reported to have several harmful effects on the human body. However, a small number of studies have evaluated the association between shift work and adverse effects on the thyroid. In our longitudinal study, we examined the causal association between shift work and the risk of hypothyroidism.

Methods

A Kangbuk Samsung Cohort Study was conducted on 112,648 men without thyroid disease at baseline who were followed up at least once between 2012 and 2019. Shift work status and shift schedule types were categorized using standardized questionnaires. Hypothyroidism was defined using the reference ranges of serum thyroid-stimulating hormones and free thyroxine levels. Hazard ratios (HRs) and 95% confidence intervals (CIs) for incident hypothyroidism were estimated using Cox proportional hazards regression analyses with the daytime work group as the reference.

Results

During the 501,237 person-years of follow-up, there were 6,306 incident cases of hypothyroidism (incidence density, 1.26 per 100 person-years). The multivariable-adjusted HR of incident hypothyroidism for the shift work total group that included all shifts compared with the daytime work group was 1.27 (95% CI: 1.15-1.40). For the fixed evening, fixed night, rotating shift, and other shift workers, the multivariable-adjusted HRs (95% CI) were 1.11 (0.76-1.61), 2.18 (1.20-3.93), 1.39 (1.23-1.56), and 1.00 (0.82-1.22), respectively. In subgroup analyses by age, the association between shift work and hypothyroidism was more pronounced in younger participants (< 40 years; HR: 1.31; 95% CI: 1.16-1.47).

Conclusions

Our large-scale cohort study showed an association between shift work and the incidence of hypothyroidism, especially in younger workers with night shifts.

Exposure to perfluoroalkyl substances (PFAS) and association with thyroid hormones in adolescent males

BACKGROUND

Perfluoroalkyl substances (PFAS) are found in a wide range of consumer products. Exposure to PFAS in children and adolescents may be associated with alterations in thyroid hormones, which have critical roles in brain function.

OBJECTIVE

This study investigated the association between plasma concentrations of PFAS and serum levels of total triiodothyronine (T3), free thyroxine (T4), and thyroid-stimulating hormone (TSH) in adolescent males.

METHODS

In 2017-2019, 151 boys from the Environment and Childhood (INMA)-Granada birth cohort, Spain, participated in a clinical follow up visit at the age of 15-17 years. Plasma concentrations of ten PFAS (PFHxA, PFHpA, PFOA, PFNA, PFDA, PFUnDA, PFDoDA, PFTrDA, PFOS, and PFHxS) and serum thyroid hormones were measured in 129 of these boys. Linear regression analysis was performed to determine associations of individual PFAS with total T3, free T4, TSH, and free T4/TSH ratio, and quantile g-computation models were performed to assess the mixture effect. Additional models considered iodine status as effect modifier.

RESULTS

PFOS was the most abundant PFAS in plasma (median = 2.22 μg/L), followed by PFOA (median = 1.00 μg/L), PFNA (median = 0.41 μg/L), and PFHxS (median = 0.40 μg/L). When adjusted by confounders (including age, maternal schooling, and fish intake), PFOA and PFUnDA were associated with an increase in free T4 (β [95% CI] = 0.72 [0.06; 1.38] and 0.36 [0.04; 0.68] pmol/L, respectively, per two-fold increase in plasma concentrations), with no change in TSH. PFOS, the sum of PFOA, PFNA, PFOS, and PFHxS, and the sum of long-chain PFAS were marginally associated with increases in free T4. Associations with higher free T4 and/or total T3 were seen for several PFAS in boys with lower iodine intake (<108 μ/day) alone. Moreover, the PFAS mixture was association with an increase in free T4 levels in boys with lower iodine intake (% change [95% CI] = 6.47 [-0.69; 14.11] per each quartile increase in the mixture concentration).

CONCLUSIONS

Exposure to PFAS, considered individually or as a mixture, was associated with an increase in free T4 levels in boys with lower iodine intake. However, given the small sample size, the extent of these alterations remains uncertain.