Complex alteration of thyroid function in healthy centenarians

Hypothyroidism in Older Adults: A Narrative Review

INTRODUCTION

The prevalence of hypothyroidism increases along with aging, resulting in one of the most common comorbidities among patients over 75 years. The leading causes of hypothyroidism in older adults are iatrogenic, Hashimoto's thyroiditis, and medications. The narrative review aimed to discuss the clinical characteristics of hypothyroidism in older adults and the impact of hormonal replacement therapy on survival rates. Thyroid function declines over time due to physiological changes in the thyroid stimulating hormone signaling, iodine absorption and metabolism, thyroid hormone metabolism, and activity at peripheral sites. A serum TSH value over the upper limit of the normal reference range is not necessarily attributable to hypothyroidism. However, an appropriate diagnostic work-up is required to rule out true hypothyroidism and discriminate the etiology (i.e., thyroid autoimmune diseases, iodine deficiency, drug-induced hypothyroidism). Levothyroxine treatment should be considered in cases of overt hypothyroidism. A complete risk-to-benefit assessment, particularly considering the overall health status, life expectancy, cognitive function, mood, and cardiovascular and neurological background, should be considered before treating subclinical hypothyroidism with more potential benefits in patients under 75 years old. Levothyroxine formulations facilitating hormone absorption and increasing compliance to long-term treatment should be preferred. TSH target should usually be set over 3 mIU/ml. Defining optimal diagnostic approaches and targeted therapeutic strategies should be considered in the personalized management of aged patients with hypothyroidism.

Chinese Medicine Supplementing Qi and Activating Blood Circulation Relieves the Progression of Diabetic Cardiomyopathy

BACKGROUND

Diabetic cardiomyopathy (DCM) is the leading cause of diabetic death as the final occurrence of heart failure and arrhythmia. Traditional Chinese medicine is usually used to treat various diseases including diabetes.

OBJECTIVE

This study sought to investigate the effects of Traditional Chinese medicine supplementing Qi and activating blood circulation (SAC) in DCM.

METHODS

After the construction of the DCM model by streptozotocin (STZ) injection and high glucose/fat diet feeding, rats were administered intragastrically with SAC. Then, cardiac systolic/diastolic function was evaluated by detecting left ventricular systolic pressure (LVSP), maximal rate of left ventricular pressure rise (+LVdp/dtmax), and fall (-LVdp/dtmax), heart rate (HR), left ventricular ejection fraction (EF), LV fractional shortening (FS) and left ventricular end-diastolic pressure (LVEDP). Masson’s and TUNEL staining were used to assess fibrosis and cardiomyocyte apoptosis.

RESULTS

DCM rats exhibited impaired cardiac systolic/diastolic function manifested by decreasing LVSP, + LVdp/dtmax, -LVdp/dtmax, HR, EF and FS, and increasing LVEDP. Intriguingly, traditional Chinese medicine SAC alleviated the above-mentioned symptoms, indicating a potential role in improving cardiac function. Masson’s staining substantiated that SAC antagonized the increased collagen deposition and interstitial fibrosis area and the elevations in protein expression of fibrosis-related collagen I and fibronectin in heart tissues of DCM rats. Furthermore, TUNEL staining confirmed that traditional Chinese medicine SAC also attenuated cardiomyocyte apoptosis in DCM rats. Mechanically, DCM rats showed the aberrant activation of the TGF-β/Smad signaling, which was inhibited after SAC.

CONCLUSION

SAC may exert cardiac protective efficacy in DCM rats via the TGF-β/Smad signaling, indicating a new promising therapeutic approach for DCM.

Update on subclinical thyroid dysfunction

Subclinical thyroid dysfunction is defined by serum thyroid-stimulating hormone (TSH) levels either greater or less than the reference range with normal thyroxine (T4) concentrations, and consists of subclinical hypothyroidism (SCH) and subclinical hyperthyroidism (SCHyper). For the proper diagnosis of SCH, it is most important to be able to correctly evaluate the serum TSH levels, which have numerous unique characteristics. We also need to be versed in TSH harmonization, which was recently launched world-wide. In this review, we will attempt to determine the best clinical approaches to the treatment of subclinical thyroid dysfunction based on recent guidelines published from several countries and novel findings of several recent large-scale clinical studies.

Thyroid function and age-related decline in kidney function in older Chinese adults: a cross-sectional study

Background

Thyroid function may be a factor affecting kidney function in the general population. Kidney and thyroid function vary with age; therefore, the association between thyroid function and decreased kidney function in older adults may be different from that in younger adults and remains controversial. This study aimed to estimate the association between normal-range thyroid function and age-related decline in kidney function in older Chinese adults.

Methods

A total of 15,653 adults, of whom 23.2% (N = 3624) were older adults (age≧65 years), were collected at the Health Management Center of the First Affiliated Hospital of Nanjing Medical University from January 2018 to January 2020. Basic demographic information was collected by a physician-administered questionnaire. The estimated glomerular filtration rate (eGFR) was calculated using the CKD-EPI formula. Trends in thyroid function with age were shown by means of free triiodothyronine (FT3), free thyroxine (FT4), and thyroid-stimulating hormone (TSH) in subgroups every ten years. The association between kidney function and thyroid function was estimated by multiple linear regression using β value and by multivariable logistic regression models using odds ratios (OR) after adjusting for age, gender, body mass index, and serum urine acid.

Results

In the older population, TSH tended to increase with age and FT3 tended to decrease, whereas FT4 was relatively stable. eGFR decreased significantly with increasing TSH (β = -0.081) and decreasing FT3 (β = 0.083) concentrations. Compared with those in the lowest quartile of FT3 (3.10–4.47 pmol/L), the prevalence of eGFR < 75 ml/min/1.73m² decreased significantly by 22.0% for those with FT3 of 4.47–4.81 pmol/L, 27.6% for those with FT3 of 4.82–5.20 pmol/L, and 34.9% for those with FT3 of 5.21–6.8 pmol/L in older individuals (P for trend < .001). The OR was 1.315 (P: 0.025) in subjects with high-normal TSH, using low-normal TSH as a reference. The prevalence of reduced kidney function was not significantly associated with FT4 within the reference range. Similar results were found in association between the prevalence of eGFR < 60 ml/min/1.73m² and thyroid function.

Conclusions

This study demonstrated a significant association between kidney function and thyroid function, particularly FT3, in the older population. Clinicians may need to pay more attention to the assessment and follow-up of kidney function in older individuals with low-normal FT3 and high-normal TSH.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-022-02904-z.

Systemic Lupus Erythematosus Patients With Related Organic Damage Are at High Risk of Hypothyroidism

PURPOSE

The aim of this study included determining the prevalence of hypothyroidism in patients with systemic lupus erythematosus (SLE), clarifying the clinical characteristics of SLE patients with hypothyroidism, and identifying the relationship between hypothyroidism and SLE-related organic damage. Another purpose was to analyze the relationship between SLE and thyroid autoantibody. We also intended to discuss the pathogenesis of hypothyroidism in SLE patients, which would provide clues for further investigation.

METHODS

This study recruited 856 SLE patients and 856 age- and sex-matched healthy population and compared the prevalence of hypothyroidism between the cases and controls. Univariate and multivariate logistic analyses were applied to identify risk factors for hypothyroidism in SLE patients.

RESULTS

SLE patients had higher prevalence of clinical hypothyroidism (9.10%) and TgAb+TPOAb- (10.40%) than controls. The prevalence of hypothyroidism was the highest in SLE patients aged 16-26 years (18.9%) and decreased with age. The prevalence of autoimmune hypothyroidism in SLE group was higher than that in the control group (64.4% vs. 51.5%, P=0.042), which was mainly due to TgAb; the prevalence of non-autoimmune hypothyroidism in SLE group was also significantly higher than that in the control group (67.3% vs. 47.8%, P<0.001). Based on multivariate analysis, the use of glucocorticoids/immunosuppressants, liver abnormality, lupus nephritis (LN), and cardiac insufficiency were independently associated with hypothyroidism in SLE patients.

CONCLUSION

The prevalence of hypothyroidism in SLE patients was higher than that in controls and decreased with age. The results suggested that young SLE patients combined with LN, liver abnormality and cardiac insufficiency were at higher risk of hypothyroidism. According to the results of this study, we speculated that SLE might have impact on thyroid, and SLE might be one of the causes of hypothyroidism.

Transient high thyroid stimulating hormone and hypothyroidism incidence during follow up of subclinical hypothyroidism

Objectives. Given the high prevalence of subclinical hypothyroidism (SCH), defined as high thyroid stimulating hormone (TSH) and normal free thyroxine (FT4), and uncertainty on treatment, one of the major challenges in clinical practice is whether to initiate the treatment for SCH or to keep the patients under surveillance. There is no published study that has identified predictors of short-term changes in thyroid status amongst patients with mild elevation of TSH (4.5-10 mIU/L). Subjects and Results. A cohort study was conducted on patients with SCH detected through a general population screening program, who were followed for six months. This project identified factors predicting progression to hypothyroid status, persistent SCH and transient cases. A total of 656 participants joined the study (431 controls and 225 were patients with SCH). A part of participants (12.2%) developed biochemical hypothyroidism during the follow-up, while 73.8% of the subjects became euthyroid and the remained ones (13.4%) stayed in the SCH status. The incidence of overt hypothyroidism for participants with TSH above 6.9 mIU/L was 36.7%, with incidence of 42.3% for females. Anti-thyroid peroxidase antibodies (TPO) positivity is an important predictor of development of hypothyroidism; however, it could be also positive due to transient thyroiditis. Conclusions. It can be concluded that females with TSH above 6.9 mIU/L, particularly those with free triiodothyronine (FT3) and FT4 in the lower half of the reference range, are more likely to develop biochemical hypothyroidism. Therefore, it is recommended to give them a trial of levothyroxine replacement. It is also recommended to repeat TSH after six months for male subjects and participants with baseline TSH equal or less than 6.9 mIU/L.

Thyroid stimulating hormone levels and geriatric syndromes: secondary nested case-control study of the Mexican Health and Aging Study

PURPOSE

To determine the incidence of geriatric syndromes (GS) in community dwelling older adults with subclinical hypothyroidism.

METHODS

This is an analysis from the Mexican Health and Aging Study, of a subsample of 2089 subjects with TSH determination. From this last subsample, we included 1628 individuals with TSH levels in the subclinical range (4.5-10 µU/ml).

RESULTS

The multivariate analysis showed that when comparing data obtained from the 2012 wave with the 2015 wave results, there was a significant incidence of some GS such as falls (OR 1.79, CI 1.16-2.77, p = 0.0116), fatigue (OR 2.17, CI 1.40-3.38, p = 0.0348) and depression (OR 1.70, CI 1.06-2.71, p = 0.0246) among the subclinical hypothyroidism group.

CONCLUSION

This study showed a greater incidence of GS in subjects 50 years and older with sub-clinical hypothyroidism, when compared to those with normal thyroid function.

Nutrition for Older Athletes: Focus on Sex-Differences

Regular physical exercise and a healthy diet are major determinants of a healthy lifespan. Although aging is associated with declining endurance performance and muscle function, these components can favorably be modified by regular physical activity and especially by exercise training at all ages in both sexes. In addition, age-related changes in body composition and metabolism, which affect even highly trained masters athletes, can in part be compensated for by higher exercise metabolic efficiency in active individuals. Accordingly, masters athletes are often considered as a role model for healthy aging and their physical capacities are an impressive example of what is possible in aging individuals. In the present review, we first discuss physiological changes, performance and trainability of older athletes with a focus on sex differences. Second, we describe the most important hormonal alterations occurring during aging pertaining regulation of appetite, glucose homeostasis and energy expenditure and the modulatory role of exercise training. The third part highlights nutritional aspects that may support health and physical performance for older athletes. Key nutrition-related concerns include the need for adequate energy and protein intake for preventing low bone and muscle mass and a higher demand for specific nutrients (e.g., vitamin D and probiotics) that may reduce the infection burden in masters athletes. Fourth, we present important research findings on the association between exercise, nutrition and the microbiota, which represents a rapidly developing field in sports nutrition.

Heterogeneity and Dynamics of Vasculature in the Endocrine System During Aging and Disease

The endocrine system consists of several highly vascularized glands that produce and secrete hormones to maintain body homeostasis and regulate a range of bodily functions and processes, including growth, metabolism and development. The dense and highly vascularized capillary network functions as the main transport system for hormones and regulatory factors to enable efficient endocrine function. The specialized capillary types provide the microenvironments to support stem and progenitor cells, by regulating their survival, maintenance and differentiation. Moreover, the vasculature interacts with endocrine cells supporting their endocrine function. However, the structure and niche function of vasculature in endocrine tissues remain poorly understood. Aging and endocrine disorders are associated with vascular perturbations. Understanding the cellular and molecular cues driving the disease, and age-related vascular perturbations hold potential to manage or even treat endocrine disorders and comorbidities associated with aging. This review aims to describe the structure and niche functions of the vasculature in various endocrine glands and define the vascular changes in aging and endocrine disorders.

Study of reference intervals for free triiodothyronine, free thyroxine, and thyroid-stimulating hormone in an elderly Chinese Han population

The clinical manifestations of thyroid diseases in elderly patients are often atypical. This study aimed to establish reference intervals for thyroid function in the elderly in order to help diagnose thyroid diseases in this population. A total of 5345 healthy individuals were examined and divided into three groups according to their age: 4297 individuals aged < 65 years (19–64), 719 individuals aged between 65 and 79 years, and 329 individuals aged between 80 and 100 years. Levels of free triiodothyronine (FT3), free thyroxine (FT4), thyroid-stimulating hormone (TSH), thyroid peroxidase antibody, and thyroglobulin antibody were measured in these subjects by using a fully automated analyzer. The following free triiodothyronine, free thyroxine, and thyroid-stimulating hormone reference intervals were obtained from each age group: For individuals aged < 65 years (19–64 years), FT3, FT4, and TSH were 3.40–6.44, 10.26–19.25 pmol/L and 0.50–4.81 μIU/mL, respectively. For individuals aged between 65 and 79 years, FT3, FT4 and TSH ranged between 3.01–5.91, 10.04–19.76 pmol/L, and 0.54–5.51 μIU/mL, respectively. For individuals aged between 80 and 100 years, FT3, FT4, and TSH varied between 2.82–5.57, 9.79–21.22 pmol/L, 0.31–6.28 μIU/mL respectively. FT3 concentration was lower and the concentrations of FT4 and TSH were higher in individuals aged ≥ 65 years than in those aged <65 years (P<0.0001; P = 0.0039; P<0.0001, respectively). In conclusion, establishment of a reference interval would allow clinicians to diagnose diseases more accurately and easily.

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.

Age-Related Resistance to Thyroid Hormone Action

The age-related resistance to thyroid hormones (THs) explains the paucity of symptoms and signs of hyperthyroidism in older adults and may partly explain the myriad of symptoms and signs of hypothyroidism in biochemically euthyroid older people. This review considers the available data on the mechanisms underlying TH resistance with aging and compares these physiologic changes with the changes observed in congenital TH resistance syndromes. Aging is associated with alterations in TH economy along with a host of changes in the responsiveness of various tissues to THs. The age-related resistance to THs can be attributed to decreased TH transport to tissues, decreased nuclear receptor occupancy, decreased activation of thyroxine to triiodothyronine, and alterations in TH responsive gene expression. Although an increase in serum TH levels is expected in syndromes of TH resistance, unchanged serum TH levels in the euthyroid elderly is the result of increased sensitivity to TH negative feedback with increased suppression of thyroid-stimulating hormone, decreased thyroidal sensitivity to thyroid-stimulating hormone, and decreased TH production and secretion. The current clinical evidence suggests that the age-related TH resistance is mostly an adaptive response of the aging organism. It is tempting to speculate that similar changes can occur prematurely in a group of younger people who present with signs and symptoms of hypothyroidism despite normal serum thyroid function tests.

ROLE of IGF-1 System in the Modulation of Longevity: Controversies and New Insights From a Centenarians' Perspective

Human aging is currently defined as a physiological decline of biological functions in the body with a continual adaptation to internal and external damaging. The endocrine system plays a major role in orchestrating cellular interactions, metabolism, growth, and aging. Several in vivo studies from worms to mice showed that downregulated activity of the GH/IGF-1/insulin pathway could be beneficial for the extension of human life span, whereas results are contradictory in humans. In the present review, we discuss the potential role of the IGF-1 system in modulation of longevity, hypothesizing that the endocrine and metabolic adaptation observed in centenarians and in mammals during caloric restriction may be a physiological strategy for extending lifespan through a slower cell growing/metabolism, a better physiologic reserve capacity, a shift of cellular metabolism from cell proliferation to repair activities and a decrease in accumulation of senescent cells. Therefore, understanding of the link between IGF-1/insulin system and longevity may have future clinical applications in promoting healthy aging and in Rehabilitation Medicine.

Overt and Subclinical Hypothyroidism in the Elderly: When to Treat?

Hypothyroidism is characterized by increased thyrotropin (TSH) levels and reduced free thyroid hormone fractions while, subclinical hypothyroidism (sHT) by elevated serum TSH in the face of normal thyroid hormones. The high frequency of hypothyroidism among the general population in Western Countries made levothyroxine (LT4) one of the 10 most prescribed drugs. However, circulating TSH has been demonstrated to increase with aging, regardless the existence of an actual thyroid disease. Thus, when confronting an increase in circulating TSH levels in the elderly, especially in the oldest old, it is important to carry an appropriate diagnostic path, comprehensive of clinical picture as well as laboratory and imaging techniques. In the current review, we summarize the recommendations for a correct diagnostic workup and therapeutic approach to older people with elevated TSH value, with special attention to the presence of frailty, comorbidities, and poly-therapy. The treatment of choice for hypothyroid patients is hormone replacement with LT₄ but, it is important to consider multiple factors before commencing the therapy, from the age dependent TSH increase to the presence of an actual thyroid disease and comorbidities. When treatment is necessary, a tailored therapy should be chosen, considering poly-pharmacy and frailty. A careful follow-up and treatment re-assessment should be always considered to avoid the risk of over-treatment. It is important to stress the need of educating the patient for a correct administration of LT₄, particularly when poly-therapy is in place, and the importance of a tailored therapeutic approach and follow-up, to avoid overtreatment.

Hypothyroidism in the Elderly: Who Should Be Treated and How?

Hypothyroidism is among the most frequent chronic diseases in the elderly, and levothyroxine (l-T4) is worldwide within the 10 drugs more prescribed in the general population. Hypothyroidism is defined by increased serum thyroid-stimulating hormone (TSH) values and reduced circulating free thyroid hormones, whereas subclinical hypothyroidism (sHT) is characterized by free hormone fractions within the normal ranges and has been divided into two classes, depending on circulating TSH levels (above or below 10 mIU/L). Given that during aging, a natural trend toward higher values of circulating TSH has been reported, it is necessary to verify carefully the diagnosis of sHT to tailor an appropriate follow-up and ad hoc therapy, avoiding unnecessary or excessive treatment. In the current review, we evaluate the state of the art on hypothyroidism in the elderly with special focus on the effect of sHT on cognition and the cardiovascular system function. We also summarize the recommendations for a correct diagnostic workup and therapeutic approach to older people with an elevated TSH value, with special attention to the presence of frailty, comorbidities, and poly therapy. In conclusion, personalized therapy is crucial in good clinical practice, and in the management of older patients with sHT, multiple factors must be considered, including age-dependent TSH cutoffs, thyroid autoimmunity, the burden of comorbidities, and the possible presence of frailty. l-T4 is the drug of choice for the treatment of hypothyroid older people, but the risk of overtreatment, potential adverse drug reactions, and patient compliance should always be considered and thyroid status periodically reassessed.

Reference intervals for thyrotropin in an area of Northern Italy: the Pordenone thyroid study (TRIPP)

PURPOSE

Thyrotropin (TSH) is the most accurate marker of thyroid dysfunction in the absence of pituitary or hypothalamic disease. Studies on TSH reference intervals (RIs) showed wide inter-individual variability and prompted an intense debate about the best estimation of TSH RIs.

DESIGN

We performed a population study on TSH RIs, using current data stored in the laboratory information system (LIS), at the Hospital Department of Laboratory Medicine, Pordenone (Italy), historically an area of mild-moderate iodine deficiency with a relatively high goiter prevalence.

METHODS

136,650 individuals constituted the final sample. A TSH immunoassay was performed on fasting serum samples with the Dimension Vista 1500 analyzer (Siemens Healthineers). We adopted the Kairisto's procedure to analyze TSH data downloaded by the LIS, applying the indirect strategy for deriving RIs.

RESULTS

TSH RIs of the entire population were 0.32-3.36 mIU/L with a distribution skewed towards higher values. RIs were 0.26-3.61 mIU/L for females, and 0.32-3.01 mIU/L for males. Unlike other studies, TSH median levels progressively decreased from 0-4 to 85-104 years in the overall population, both in male and in female subgroups, showing an inverse correlation between TSH and age in all groups.

CONCLUSIONS

This study is the first to analyze a high percentage (40%) of individuals from an ethnically homogenous Caucasian population. The results obtained emphasize the opportunity to define the TSH RIs according to age, gender and race, in addition to assay methods, and provide further insight about the possible role of iodine status.

3,3'-Diiodothyronine concentrations in hospitalized or thyroidectomized patients: results from a pilot study

OBJECTIVE

To determine if various medical conditions affect the serum concentrations of 3,3'-diiodothyronine (3,3'-T2).

METHODS

A total of 100 patients who were recruited from a group of inpatients and outpatients with a diverse range of medical conditions, donated a single blood sample that was assayed for thyroid hormone derivatives using liquid-chromatography tandem mass spectrometry (LC-MS/MS). The associations between 3,3'-T2 concentrations and physiologic data and medical conditions were assessed.

RESULTS

Higher quartiles of 3,3'-T2 concentrations (quartile 1: 2.01-7.48, quartile 2: 7.74-12.4, quartile 3: 12.5-17, quartile 4: 17.9-45.8 pg/mL) were associated with decreasing occurrence of critical illness (58%, 11%, 0%, 8%), stroke (29%, 7.7%, 4%, 0%), critical care unit hospitalization (75%, 39%, 8.3 %, 12%), and inpatient status (83%, 42%, 8%, 12%) (all P<.001). The same quartiles were associated with increasing frequency of thyroidectomy (4%, 12%, 17%, 60%). In multivariate analyses, after adjustment for age and sex, inpatient status was associated with decreasing concentrations of 3,3'-T2 (46% decrease for inpatients with 95% confidence interval [CI] 32-57%, P<.0001). Thyroidectomy was associated with increasing concentrations of 3,3'-T2 (29% increase (CI 0.5-66%, P = .049).

CONCLUSION

We observed associations between inpatient status and reduced 3,3'-T2 concentrations. This appears to be a global change associated with illness, rather than an association with specific medical conditions. We also observed higher 3,3'-T2 concentrations in athyreotic outpatients receiving thyroid-stimulating hormone (TSH) suppression therapy. This demonstrates that there is production of 3,3'-T2 from levothyroxine (LT4) in extrathyroidal tissues. Conversion of thyroxine (T4) to 3,3'-T2 via both triiodothyronine (T3) and reverse triiodothyronine (rT3) pathways may prevent excessive T3 concentrations in such patients.

The 2015 European Thyroid Association Guidelines on Diagnosis and Treatment of Endogenous Subclinical Hyperthyroidism

Endogenous subclinical hyperthyroidism (SHyper) is caused by Graves' disease, autonomously functioning thyroid nodules and multinodular goitre. Its diagnosis is based on a persistently subnormal serum thyroid-stimulating hormone (TSH) level with free thyroid hormone levels within their respective reference intervals. In 2014 the European Thyroid Association Executive Committee, given the controversies regarding the treatment of Endo SHyper, formed a task force to develop clinical practice guidelines based on the principles of evidence-based medicine. The task force recognized that recent meta-analyses, including those based on large prospective cohort studies, indicate that SHyper is associated with increased risk of coronary heart disease mortality, incident atrial fibrillation, heart failure, fractures and excess mortality in patients with serum TSH levels <0.1 mIU/l (grade 2 SHyper). Therefore, despite the absence of randomized prospective trials, there is evidence that treatment is indicated in patients older than 65 years with grade 2 SHyper to potentially avoid these serious cardiovascular events, fractures and the risk of progression to overt hyperthyroidism. Treatment could be considered in patients older than 65 years with TSH levels 0.1-0.39 mIU/l (grade 1 SHyper) because of their increased risk of atrial fibrillation, and might also be reasonable in younger (<65 years) symptomatic patients with grade 2 SHyper because of the risk of progression, especially in the presence of symptoms and/or underlying risk factors or co-morbidity. Finally, the task force concluded that there are no data to support treating SHyper in younger asymptomatic patients with grade 1 SHyper. These patients should be followed without treatment due to the low risk of progression to overt hyperthyroidism and the weaker evidence for adverse health outcomes.

Homeostatic Control of the Thyroid-Pituitary Axis: Perspectives for Diagnosis and Treatment

The long-held concept of a proportional negative feedback control between the thyroid and pituitary glands requires reconsideration in the light of more recent studies. Homeostatic equilibria depend on dynamic inter-relationships between thyroid hormones and pituitary thyrotropin (TSH). They display a high degree of individuality, thyroid-state-related hierarchy, and adaptive conditionality. Molecular mechanisms involve multiple feedback loops on several levels of organization, different time scales, and varying conditions of their optimum operation, including a proposed feedforward motif. This supports the concept of a dampened response and multistep regulation, making the interactions between TSH, FT4, and FT3 situational and mathematically more complex. As a homeostatically integrated parameter, TSH becomes neither normatively fixed nor a precise marker of euthyroidism. This is exemplified by the therapeutic situation with l-thyroxine (l-T4) where TSH levels defined for optimum health may not apply equivalently during treatment. In particular, an FT3-FT4 dissociation, discernible FT3-TSH disjoint, and conversion inefficiency have been recognized in l-T4-treated athyreotic patients. In addition to regulating T4 production, TSH appears to play an essential role in maintaining T3 homeostasis by directly controlling deiodinase activity. While still allowing for tissue-specific variation, this questions the currently assumed independence of the local T3 supply. Rather it integrates peripheral and central elements into an overarching control system. On l-T4 treatment, altered equilibria have been shown to give rise to lower circulating FT3 concentrations in the presence of normal serum TSH. While data on T3 in tissues are largely lacking in humans, rodent models suggest that the disequilibria may reflect widespread T3 deficiencies at the tissue level in various organs. As a consequence, the use of TSH, valuable though it is in many situations, should be scaled back to a supporting role that is more representative of its conditional interplay with peripheral thyroid hormones. This reopens the debate on the measurement of free thyroid hormones and encourages the identification of suitable biomarkers. Homeostatic principles conjoin all thyroid parameters into an adaptive context, demanding a more flexible interpretation in the accurate diagnosis and treatment of thyroid dysfunction.

Cardiovascular risk and quality of life in elderly people with mild thyroid hormone deficiency

Subclinical hypothyroidism (sHT) is a common condition in the general population, the prevalence increases with age, especially in women. An association between sHT and increased coronary heart disease (CHD) and heart failure (HF) risk and mortality has been described. However, this association is far to be established in older people (>65 years), especially in the oldest old (>85 years). Individuals with sHT may experience symptoms that resemble those observed in the overt form of the disease, leading to an impaired quality of life (QoL). Although very old people are frequently frail and potentially more susceptible to the effects of a disease, few studies were designed to assess the effect of sHT on QoL in this subset of population. Interestingly, the serum TSH concentration curve of general population has a skewed distribution with a "tail" toward higher values, which is amplified with aging. Thus, the diagnosis of sHT and the interpretation of its potential effects on CV function and QoL in older people may be a challenge for the clinician. Giving these premises, we reviewed the English scientific literature available on National Library of Medicine (www.pubmed.com) since 1980 regarding hypothyroidism, sHT, elderly, cardiovascular risk, CHD or HF events and mortality, health-related QoL, and LT4 therapy. Consistent results among large prospective cohort studies suggest an age-independent relationship between sHT and HF progression, while an impact of sHT on CHD events and mortality is essentially reported in young adults (aged below 65-70 years) with long-lasting disease. Scanty data are available on QoL of older people with sHT (>65 years) and, generally, no significant alterations are described.

The clinical consequences of an ageing world and preventive strategies

Over the past century, the world has seen unprecedented declines in mortality rates, leading to an accelerated increase in the world population. This century will realise falling fertility rates alongside ageing populations. The 20th century was the century of population growth; the 21st century will be remembered as the century of ageing. Increase in life expectancy is one of the highest achievements of humankind; however, ageing and age-related disease is a mounting challenge for individuals, families, and for social, economic, and healthcare systems. Since healthy life expectancy has lagged behind the increase in life expectancy, the rise in morbidity will increase the burden on healthcare systems. Implementation of preventive health strategies to decrease, delay or prevent frailty, lung, breast and colon cancer, cardiovascular disease, metabolic syndrome, osteoporosis and osteopaenia, may increase health expectancy, and permit women to age gracefully and maintain independent living, without disability, for as long as possible.

Exploring the role of genetic variability and lifestyle in oxidative stress response for healthy aging and longevity

Oxidative stress is both the cause and consequence of impaired functional homeostasis characterizing human aging. The worsening efficiency of stress response with age represents a health risk and leads to the onset and accrual of major age-related diseases. In contrast, centenarians seem to have evolved conservative stress response mechanisms, probably derived from a combination of a diet rich in natural antioxidants, an active lifestyle and a favorable genetic background, particularly rich in genetic variants able to counteract the stress overload at the level of both nuclear and mitochondrial DNA. The integration of these factors could allow centenarians to maintain moderate levels of free radicals that exert beneficial signaling and modulator effects on cellular metabolism. Considering the hot debate on the efficacy of antioxidant supplementation in promoting healthy aging, in this review we gathered the existing information regarding genetic variability and lifestyle factors which potentially modulate the stress response at old age. Evidence reported here suggests that the integration of lifestyle factors (moderate physical activity and healthy nutrition) and genetic background could shift the balance in favor of the antioxidant cellular machinery by activating appropriate defense mechanisms in response to exceeding external and internal stress levels, and thus possibly achieving the prospect of living a longer life.

Oxidative stress and the ageing endocrine system

Ageing is a process characterized by a progressive decline in cellular function, organismal fitness and increased risk of age-related diseases and death. Several hundred theories have attempted to explain this phenomenon. One of the most popular is the 'oxidative stress theory', originally termed the 'free radical theory'. The endocrine system seems to have a role in the modulation of oxidative stress; however, much less is known about the role that oxidative stress might have in the ageing of the endocrine system and the induction of age-related endocrine diseases. This Review outlines the interactions between hormones and oxidative metabolism and the potential effects of oxidative stress on ageing of endocrine organs. Many different mechanisms that link oxidative stress and ageing are discussed, all of which converge on the induction or regulation of inflammation. All these mechanisms, including cell senescence, mitochondrial dysfunction and microRNA dysregulation, as well as inflammation itself, could be targets of future studies aimed at clarifying the effects of oxidative stress on ageing of endocrine glands.

Longitudinal changes in thyroid function in the oldest old and survival: the cardiovascular health study all-stars study

CONTEXT

Data on thyroid function in the oldest old are sparse, and existing studies show conflicting evidence on the relationship between thyroid function and mortality in this age group.

OBJECTIVE

We describe longitudinal changes in thyroid function in a cohort of elderly individuals and determine the relationship between thyroid function and mortality.

DESIGN, SETTING, AND PARTICIPANTS

Eight hundred forty-three participants in the Cardiovascular Health Study All Stars Study who were not taking thyroid medications and had thyroid function testing in 2005-2006 (mean age 85 yr).

MAIN OUTCOME MEASURE

Thyroid-stimulating hormone (TSH), free T(4) (FT4), total T(3), and thyroid peroxidase antibody status were measured in 1992-1993 and 2005-2006. Deaths were ascertained through February 2011.

RESULTS

There was a statistically significant 13% increase in TSH, 1.7% increase in FT4, and 13% decrease in total T(3) over the 13-yr period. Two hundred eighty-seven deaths occurred over a median follow-up of 5.1 yr. There was no association between subclinical hypothyroidism[hazard ratio (HR) 0.97, 95% confidence interval (CI) 0.66-1.43], TSH level (HR per milliunits per liter 0.94, 95% CI 0.88-1.01), or persistent thyroid peroxidase antibody positivity (HR 1.09, 95% CI 0.62-1.92), and death. However, FT4 was positively associated with death (HR per nanograms per deciliter 2.57, 95% CI 1.32-5.02).

CONCLUSIONS

TSH increased over time in these older individuals. This elevation was not associated with increased or decreased mortality, although higher FT4 levels were associated with death. These findings raise concern for treatment of mild elevations of TSH in advanced age. Further studies are needed to determine the potential benefit of treating age-related changes in thyroid function.

Clinical review: The thyroid in mind: cognitive function and low thyrotropin in older people

CONTEXT

Several studies have reported an association between low serum TSH, or subclinical hyperthyroidism (SH), and dementia, but little emphasis has been placed on this field because not all studies have demonstrated the same association. We performed a detailed systematic review to assess the evidence available to support the association between these two conditions.

METHODS

We performed a systematic search through the PubMed, Embase (1996 to 2012 wk 4), Cochrane Library, and Medline (1996 to January wk 4, 2012) electronic databases using key search terms encompassing subclinical hyperthyroidism, TSH, dementia, and cognitive impairment.

RESULTS

This review examines the 23 studies that provide information about the association between SH or lower serum TSH within the reference range and cognition. Fourteen of these studies, including several well-designed and well-powered cross-sectional and longitudinal analyses, have shown a consistent finding of an association between SH with cognitive impairment or dementia.

CONCLUSION

There is a substantial body of evidence to support the association between SH and cognitive impairment, but there is no clear mechanistic explanation for these associations. Nor is there an indication that antithyroid treatment might ameliorate dementia. Larger and more detailed prospective longitudinal or randomized controlled trials are required to inform these important questions.

Approach to and treatment of thyroid disorders in the elderly

Thyroid gland dysfunction is prevalent in older adults and may be associated with significant morbidity if misdiagnosed and left untreated. Because of a decreased number of symptoms at presentation, an increased susceptibility to adverse events if not treated, and a greater likelihood of harm from treatment, the diagnosis and management of thyroid disorders in older adults can be challenging. This review focuses on the epidemiology, clinical presentation, risks and complications, and management of thyroid disorders in older adults, including hyperthyroidism, hypothyroidism, thyroid nodules, and thyroid cancer.

Management of subclinical hyperthyroidism

The ideal approach for adequate management of subclinical hyperthyroidism (low levels of thyroid-stimulating hormone [TSH] and normal thyroid hormone level) is a matter of intense debate among endocrinologists. The prevalence of low serum TSH levels ranges between 0.5% in children and 15% in the elderly population. Mild subclinical hyperthyroidism is more common than severe subclinical hyperthyroidism. Transient suppression of TSH secretion may occur because of several reasons; thus, corroboration of results from different assessments is essential in such cases. During differential diagnosis of hyperthyroidism, pituitary or hypothalamic disease, euthyroid sick syndrome, and drug-mediated suppression of TSH must be ruled out. A low plasma TSH value is also typically seen in the first trimester of gestation. Factitial or iatrogenic TSH inhibition caused by excessive intake of levothyroxine should be excluded by checking the patient's medication history. If these nonthyroidal causes are ruled out during differential diagnosis, either transient or long-term endogenous thyroid hormone excess, usually caused by Graves' disease or nodular goiter, should be considered as the cause of low circulating TSH levels. We recommend the following 6-step process for the assessment and treatment of this common hormonal disorder: 1) confirmation, 2) evaluation of severity, 3) investigation of the cause, 4) assessment of potential complications, 5) evaluation of the necessity of treatment, and 6) if necessary, selection of the most appropriate treatment. In conclusion, management of subclinical hyperthyroidism merits careful monitoring through regular assessment of thyroid function. Treatment is mandatory in older patients (> 65 years) or in presence of comorbidities (such as osteoporosis and atrial fibrillation).

A cross-section analysis of FT3 age-related changes in a group of old and oldest-old subjects, including centenarians' relatives, shows that a down-regulated thyroid function has a familial component and is related to longevity

Background: several studies suggest that a decreased thyroid activity might be favourable in oldest-old subjects and that subclinical thyroid hyperfunction may be detrimental.

Objectives: to verify whether declining levels of circulating thyroid hormones may contribute to longevity.

Design: cross-sectional observational study.

Setting: all subjects were born in Calabria (southern Italy) and their ancestry in the region was ascertained up to the grandparents.

Subjects: six hundred and four home-dwelling subjects (301 females, 303 males), divided into three groups: 278 individuals 60–85 years old; 179 children or nieces/nephews of centenarians who are 60–85 years old; 147 individuals older than 85 years.

Methods: thyroid function parameters were measured in the frame of a comprehensive geriatric assessment.

Results: FT3 and FT4 levels were negatively associated with age. Lower levels of FT3, FT4 and TSH were found in centenarians’ children and nieces/nephews with respect to age-matched controls. Indeed, being a relative of centenarians qualified as an independent correlate of thyroid parameters.

Conclusions: age-related subtle thyroid hypofunction (either due to a familial component or due to a reset of the thyroid function occurring between the sixth and the eighth decade of life) appears to be related to longevity.

Age and the thyrotropin response to hypothyroxinemia

CONTEXT

Some studies suggest altered pituitary functioning and TSH production with aging.

OBJECTIVE

Our objective was to test the hypothesis that less TSH production occurs despite comparable hypothyroxinemia with advancing age.

DESIGN

We retrospectively studied adult outpatients of all ages with confirmed hypothyroidism and documented their TSH and free T4 concentrations.

PARTICIPANTS

Two populations of 112 patients were subdivided into four age groups: 1) patients newly diagnosed with primary hypothyroidism and 2) thyroid cancer patients undergoing l-T4 withdrawal in preparation for diagnostic or therapeutic radioiodine.

MAIN OUTCOME MEASURE

The relationship between paired free T-4 and TSH concentrations and patient age was studied.

RESULTS

With spontaneous hypothyroidism, the mean TSH concentration decreased nonsignificantly in each ascending age group with comparable free T4 (FT4) concentrations (<35 yr, 69 mIU/liter; 35-49 yr, 49 mIU/liter; 50-64 yr, 43 mIU/liter; >64 yr, 29 mIU/liter). With iatrogenic hypothyroidism, the mean TSH concentration decreased significantly in each ascending age group (<35 yr, 156 mIU/liter; 35-49 yr, 115 mIU/liter; 50-64 yr, 74 mIU/liter; >64 yr, 46 mIU/liter; P<0.001) despite similar FT4 concentrations. The relationship between the log-transformed TSH and FT4 was significantly and inversely affected by age in multivariate analyses in both spontaneous hypothyroidism (P=0.0005) and in iatrogenic hypothyroidism (P<0.0001).

CONCLUSIONS

Age modifies the pituitary set point or response to comparably reduced free T4 concentrations, resulting in lesser serum TSH elevation in older individuals. This phenomenon occurs with both spontaneous and iatrogenic hypothyroidism. This may be an adaptive response in normal aging or a pathological alteration of pituitary function with age.

Endocrine alterations in response to calorie restriction in humans

This review focuses on research involving calorie restriction (CR) in humans and the resulting changes observed in endocrine and neuroendocrine systems. Special emphasis is given to the clinical science studies designed to investigate the effects of controlled, high-quality, energy-restricted diets on both biomarkers of longevity and on the development of chronic diseases of human aging. Prolonged CR has been shown to extend both the median and maximal lifespan in a variety of lower species such as yeast, worms, fish, rats and mice. The biological mechanisms of this lifespan extension via CR are not fully elucidated, but possibly involve significant alterations in energy metabolism, oxidative damage, insulin sensitivity and functional changes in both neuroendocrine and autonomic nervous systems. Most of the difficulty in characterizing the systemic endocrine and neuroendocrine changes with aging and CR is due to the limited capability to collect large and multiple blood samples from small animals, which are usually shorter lived, and hence the most studied. Ongoing studies of prolonged CR in humans are now making it possible to analyze changes in the "biomarkers of aging" to unravel some of the mechanisms of its anti-aging phenomenon. With the incremental expansion of research endeavors in the area of energy restriction, data on the effects of CR in non-human primates and human subjects are becoming more accessible. Detailed analyses from controlled human trials involving long-term CR will allow investigators to link observed alterations from body composition and endocrine systems down to changes in molecular pathways and gene expression, with their possible effects on aging.

Thyroid function abnormalities and cognitive impairment in elderly people: results of the Invecchiare in Chianti study

OBJECTIVES

To investigate thyroid function testing abnormalities in older persons and to explore the relationship between thyroid dysfunction and cognition.

DESIGN

Cross-sectional.

SETTING

Community-based.

PARTICIPANTS

One thousand one hundred seventy-one men and women aged 23 to 102.

MEASUREMENTS

Thyroid function was evaluated by measuring plasma concentrations of thyrotropin (TSH), free thyroxine (FT4), and free triiodothyronine (FT3). Cognition was evaluated using the Mini-Mental State Examination (MMSE). Prevalence of overt and subclinical thyroid dysfunction was evaluated in different age groups (<65 vs > or =65). Age trends in TSH, FT4, and FT3 were examined in euthyroid participants. The cross-sectional association between thyroid dysfunction and MMSE score was evaluated adjusting for confounders.

RESULTS

Subclinical hypothyroidism and subclinical hyperthyroidism were more prevalent in older than in younger participants (subclinical hypothyroidism, 3.5% vs 0.4%, P<.03; subclinical hyperthyroidism, 7.8% vs 1.9%, P<.002). In euthyroid participants, TSH and FT3 declined with age, whereas FT4 increased. Older participants with subclinical hyperthyroidism had lower MMSE scores than euthyroid subjects (22.61+/-6.88 vs 24.72+/-4.52, P<.03). In adjusted analyses, participants with subclinical hyperthyroidism were significantly more likely to have cognitive dysfunction (hazard rate=2.26, P=.003).

CONCLUSION

Subtle age-related changes in FT3, FT4, and TSH occur in individuals who remain euthyroid. Subclinical hyperthyroidism is the most prevalent thyroid dysfunction in Italian older persons and is associated with cognitive impairment.

Thyroid Function and Cognition during Aging

We summarize here the studies examining the association between thyroid function and cognitive performance from an aging perspective. The available data suggest that there may be a continuum in which cognitive dysfunction can result from increased or decreased concentrations of thyroid hormones. Clinical and subclinical hypothyroidism as well as hyperthyroidism in middle-aged and elderly adults are both associated with decreased cognitive functioning, especially memory, visuospatial organization, attention, and reaction time. Mild variations of thyroid function, even within normal limits, can have significant consequences for cognitive function in the elderly. Different cognitive deficits possibly related to thyroid failure do not necessarily follow a consistent pattern, and L-thyroxine treatment may not always completely restore normal functioning in patients with hypothyroidism. There is little or no consensus in the literature regarding how thyroid function is associated with cognitive performance in the elderly.

Thyroid antoantibodies and the response to thyrotropin releasing hormone in patients with subclinical hypothyroidism

AIM

To evaluate the clinical usefulness of the thyrotropin releasing hormone (TRH) test and estimation of thyroid autoantibody concentrations in patients with borderline raised thyroid stimulating hormone (TSH).

METHODS

The records of 34 consecutive patients with persistent borderline increased TSH (4.4-9.9 mU/l) referred to the Medical Investigation Unit were reviewed. The response of patients with thyroid autoantibodies to the TRH test was compared with that of patients with a negative antibody screen.

RESULTS

Eleven (44%) of 25 patients with positive anti-thyroid microsomal and/or thyroglobulin antibody tests and three (33%) of nine patients with a negative antibody screen had hypothyroid responses to TRH. Neither age nor sex affected the response to TRH. Basal TSH alone was poorly correlated with these indices. Twelve (35%) patients who had elevated basal TSH had a normal response to the TRH test.

CONCLUSION

Patients with positive or negative thyroid autoantibodies and an exaggerated response to the TRH test should be regarded as hypothyroid and treated with thyroxine. Patients with positive thyroid autoantibodies and normal TSH response may subsequently develop hypothyroidism and should be given long term follow up.

Thyroid disease in older patients. Diagnosis and treatment

Thyroid gland dysfunction is a relatively common clinical problem in elderly people and is associated with significant morbidity if left untreated. The clinical features of thyroid disease may be subtle, easily overlooked or misdiagnosed. Therefore, a high index of suspicion is necessary. If potentially serious sequelae are to be avoided, the selection and interpretation of thyroid function tests must be appropriate. It is particularly important to consider both the effect of concurrent illness and the effect of certain drugs on thyroid function tests. With recent methodological advances, thyroid function tests are now more reliable, though in certain situations they still need to be interpreted with caution. Once the diagnosis is established, the management of both hypothyroidism and hyperthyroidism is relatively simple and effective, though there are special considerations relating to elderly patients.