High Circulating Free Thyroxine Levels May Increase the Risk of Frailty: The Rotterdam Study

Exploring the Association between Thyroid Function and Frailty: Insights from Representative Korean Data

BACKGRUOUND

This study investigates the association between thyroid function and frailty in the old patients using representative data.

METHODS

The study was conducted using data from the Korea National Health and Nutrition Examination Survey conducted from 2013 to 2015. The study population included 2,416 participants aged 50 years and older with available thyroid function test data. Frailty assessment was performed using the Fried frailty phenotype. The prevalence of frailty was analyzed across different thyroid diseases and thyroid function parameters.

RESULTS

The significant association between thyroid dysfunction and frailty was observed in overt hyperthyroidism and subclinical hyperthyroidism. After adjusting for various factors, the association between thyroid dysfunction and frailty remained significant. On the other hand, overt hypothyroidism did not show a significant association with frailty in the adjusted analysis. For individuals with overt hyperthyroidism and subclinical hyperthyroidism, higher levels of free thyroxine (FT4) were significantly associated with an increased risk of frailty (aOR >999; 95% CI, >999 to 999). Among individuals with overt hypothyroidism, lower level of FT4 levels and high thyrotropin (TSH) levels showed a significant association with frailty risk (FT4: aOR, <0.01; TSH: aOR, 999). In participants with subclinical hypothyroidism, there were no significant associations between parameters for thyroid and frailty risk.

CONCLUSION

These findings suggest that thyroid dysfunction, particularly overt hyperthyroidism and subclinical hyperthyroidism, may be associated with an increased risk of frailty in the old patients.

Thyroid and Aging

Older adults are more vulnerable to the negative effects of excess thyroid hormone and may even be protected by lower levels of thyroid hormone. The diagnosis and management of thyroid disease in older adults needs to account for aging-related changes in function and resilliance.

Frailty and sarcopenia within the earliest national Dutch childhood cancer survivor cohort (DCCSS-LATER): a cross-sectional study

BACKGROUND

Childhood cancer survivors appear to be at increased risk of frailty and sarcopenia, but evidence on the occurrence of and high-risk groups for these aging phenotypes is scarce, especially in European survivors. The aim of this cross-sectional study was to assess the prevalence of and explore risk factors for pre-frailty, frailty, and sarcopenia in a national cohort of Dutch childhood cancer survivors diagnosed between 1963 and 2001.

METHODS

Eligible individuals (alive at the time of study, living in the Netherlands, age 18-45 years, and had not previously declined to participate in a late-effects study) from the Dutch Childhood Cancer Survivor Study (DCCSS-LATER) cohort were invited to take part in this cross-sectional study. We defined pre-frailty and frailty according to modified Fried criteria, and sarcopenia according to the European Working Group on Sarcopenia in Older People 2 definition. Associations between these conditions and demographic and treatment-related as well as endocrine and lifestyle-related factors were estimated with two separate multivariable logistic regression models in survivors with any frailty measurement or complete sarcopenia measurements.

FINDINGS

3996 adult survivors of the DCCSS-LATER cohort were invited to participate in this cross-sectional study. 1993 non-participants were excluded due to lack of response or a decline to participate and 2003 (50·1%) childhood cancer survivors aged 18-45 years were included. 1114 (55·6%) participants had complete frailty measurements and 1472 (73·5%) participants had complete sarcopenia measurements. Mean age at participation was 33·1 years (SD  7·2). 1037 (51·8%) participants were male, 966 (48·2%) were female, and none were transgender. In survivors with complete frailty measurements or complete sarcopenia measurements, the percentage of pre-frailty was 20·3% (95% CI 18·0-22·7), frailty was 7·4% (6·0-9·0), and sarcopenia was 4·4% (3·5-5·6). In the models for pre-frailty, underweight (odds ratio [OR] 3·38 [95% CI 1·92-5·95]) and obesity (OR 1·67 [1·14-2·43]), cranial irradiation (OR 2·07 [1·47-2·93]), total body irradiation (OR 3·17 [1·77-5·70]), cisplatin dose of at least 600 mg/m² (OR 3·75 [1·82-7·74]), growth hormone deficiency (OR 2·25 [1·23-4·09]), hyperthyroidism (OR 3·72 [1·63-8·47]), bone mineral density (Z score ≤-1 and >-2, OR 1·80 [95% CI 1·31-2·47]; Z score ≤-2, OR 3·37 [2·20-5·15]), and folic acid deficiency (OR 1·87 [1·31-2·68]) were considered significant. For frailty, associated factors included age at diagnosis between 10-18 years (OR 1·94 [95% CI 1·19-3·16]), underweight (OR 3·09 [1·42-6·69]), cranial irradiation (OR 2·65 [1·59-4·34]), total body irradiation (OR 3·28 [1·48-7·28]), cisplatin dose of at least 600 mg/m² (OR 3·93 [1·45-10·67]), higher carboplatin doses (per g/m²; OR 1·15 [1·02-1·31]), cyclophosphamide equivalent dose of at least 20 g/m² (OR 3·90 [1·65-9·24]), hyperthyroidism (OR 2·87 [1·06-7·76]), bone mineral density Z score ≤-2 (OR 2·85 [1·54-5·29]), and folic acid deficiency (OR 2·04 [1·20-3·46]). Male sex (OR 4·56 [95%CI 2·26-9·17]), lower BMI (continuous, OR 0·52 [0·45-0·60]), cranial irradiation (OR 3·87 [1·80-8·31]), total body irradiation (OR 4·52 [1·67-12·20]), hypogonadism (OR 3·96 [1·40-11·18]), growth hormone deficiency (OR 4·66 [1·44-15·15]), and vitamin B12 deficiency (OR 6·26 [2·17-1·81]) were significantly associated with sarcopenia.

INTERPRETATION

Our findings show that frailty and sarcopenia occur already at a mean age of 33 years in childhood cancer survivors. Early recognition and interventions for endocrine disorders and dietary deficiencies could be important in minimising the risk of pre-frailty, frailty, and sarcopenia in this population.

FUNDING

Children Cancer-free Foundation, KiKaRoW, Dutch Cancer Society, ODAS Foundation.

The Free Triiodothyronine/Free Thyroxine Ratio Is Associated with Frailty in Older Adults: A Longitudinal Multisetting Study

Background: Various models have been proposed to predict frailty, including those based on clinical criteria and phenotypes. However, a simple biomarker associated with frailty has been not yet identified. The aim of this study is to evaluate the relationship between free triiodothyronine (fT3)/free thyroxine (fT4) ratio value and the degree of frailty among three different cohorts of older individuals: (1) acutely ill hospitalized patients, (2) nursing-home (NH) residents, and (3) home-dwelling centenarians. Methods: We performed a secondary analysis of de-identified patient-level data from two prospective observational studies on acutely hospitalized older patients (Geriatric Acute Unit [GAU]), and home-dwelling centenarians (CENT), and a retrospective-prospective observational study on older NH residents. Demographic characteristics, along with a 30-items Frailty Index (FI) and serum thyrotropin, fT3 and fT4 measurements were obtained. Results: Six hundred fifteen individuals (aged 86.4 ± 8.9 years; 55.1% females) were included in the study, including 298 (48.5%) GAU, 250 (40.6%) NH, and 67 (10.9%) CENT. A significant inverse relationship between fT3/fT4 ratio and FI values was observed (ρ_s = -0.17 [confidence interval; CI: -0.092 to 0.252], p < 0.001), and this was confirmed by logistic multivariate analysis (β = -0.44, odds ratio [OR]: 0.64 [CI: 0.47-0.87], p < 0.001) (after adjustment for age, sex, and cohorts). Moreover, a progressively decreased mortality risk was associated with rising fT3/fT4 ratio (OR 0.60 [CI: 0.44-0.80] β = -0.51, p < 0.001]. Conclusions: The fT3/fT4 ratio value was inversely correlated with frailty degree and mortality risk in a large cohort of older individuals, including centenarians, regardless of their sex and clinical condition. fT3/fT4 ratio value could represent an easily measured independent biochemical marker of frailty degree in older people.

Association between thyroid hormone levels and frailty in the community-dwelling oldest-old: a cross-sectional study

BACKGROUND

Changes in thyroid hormone levels are commonly recognized characters among the elderly, which were reported to potentially influence incident frailty. Therefore, we examined the cross-sectional associations of thyroid hormones (THs) with frailty as well as the five components characterizing frailty (fatigue, resistance, ambulation, number of illnesses, and loss of weight) among the oldest-old.

METHODS

Four hundred and eighty-seven community-dwelling oldest-old from a local community in Haidian District, Beijing, participated in our recruitment campaign between April 2019 and May 2020. The primary outcomes were a definitive diagnosis of frailty according to the FRAIL scale (Fatigue, Resistance, Ambulation, Illnesses, Loss of weight) and a positive score for each frailty subdomain. Demographic information (age, sex, marital status, and educational status), comorbidities, and details on the participants' lifestyles were recorded. Serum THs including free triiodothyronin (fT3), triiodothyronine (T3), free thyroxine (fT4), and thyroxine (T4) and thyroid stimulating hormone (TSH) levels were also measured at the beginning of our study. Logistic regressions were conducted to screen for potential risk factors for frailty and its subdomains.

RESULTS

Among the total 487 subjects at enrollment, 60 (12.23%) of them were diagnosed with subclinical hypothyroidism and 110 (22.59%) of the total population scored positive for frailty. Logistic regression analyses adjusted for all potential confounders, showed that frailty was significantly associated with the serum TSH concentration (odds ratio [OR]: 1.06), fT3 concentration (OR: 0.54), and subclinical hypothyroidism score (OR: 2.18). The association between fT4 and frailty was absent in our observational study. The fT3/fT4 ratio characterizing peripheral hormone conversion was also tested to be correlated with frailty.

CONCLUSION

Subclinical hypothyroidism, higher TSH level, lower fT3 level, and decreased fT3/fT4 ratio were all associated with frailty assessed by the FRAIL scale among the community-dwelling oldest-old, suggesting a relevant role of thyroid function in aging. Future longitudinal studies are warranted to determine the casual relationship between thyroid dysfunction and frailty in the oldest-old.

Subclinical hypothyroidism in older individuals

Subclinical hypothyroidism, which is defined as a thyroid-stimulating hormone concentration higher than the reference range (generally 4·5 mIU/L or higher) with normal free thyroxine concentrations, is frequently found in older individuals. International guidelines differ in recommendations for management of subclinical hypothyroidism in older individuals. We assessed published data during the past decade on the clinical significance and treatment of subclinical hypothyroidism in individuals aged 65 years and older. Meta-analyses, randomised clinical trials, and cohort studies are discussed in this narrative Review. Studies showed no significantly increased incidence in adverse cardiovascular, musculoskeletal, or cognitive outcomes in individuals aged 65 years or older when serum thyroid-stimulating hormone concentration was 4·5-7·0 mIU/L versus a euthyroid group. Moreover, in older individuals with subclinical hypothyroidism, symptoms of hypothyroidism and cardiac and bone parameters did not improve after levothyroxine treatment. These data suggest that treatment with levothyroxine should be considered for individuals aged 65 years or older with subclinical hypothyroidism when thyroid-stimulating hormone concentration is persistently 7 mIU/L or higher and to not initiate treatment with thyroid-stimulating hormone concentrations of less than 7 mIU/L. Levothyroxine doses should be personalised according to age, comorbidities, and life expectancy.

Free thyroxine but not TSH levels are associated with decline in functional status in a cohort of geriatric outpatients

PURPOSE

To assess the associations between TSH and free thyroxine (FT4) levels and decline in functional status in euthyroid older patients at risk of frailty.

DESIGN

Longitudinal prospective study.

METHODS

Participants from the geriatric outpatient clinic of a university hospital, who fulfilled the criteria for frailty or were at risk of frailty, were recruited. Only those euthyroid, defined by age-specific reference range of TSH, were included. Serum was collected during enrollment and at the third and sixth years of follow-up to assess the mean value of all follow-up levels of serum TSH and FT4. Functional status assessing activities of daily living (ADL) and instrumental ADL were evaluated using the Katz Index and the Health Assessment Questionnaire, respectively. Functional decline was defined by a positive variation in any of the applied scales in the absence of disagreement between the scales or if the patient was institutionalized.

RESULTS

Of the 273 participants (72.5% females) enrolled (mean age 80 years old), 48 died and 102 presented functional decline at the end of follow-up (mean 3.6 ± 1.7 years). Each 0.1 ng/dL increase in baseline and mean follow-up serum FT4 levels increased the risk of functional decline by 14.1% and 7.7%, respectively. The risk of functional decline was 9 times greater with baseline FT4 levels in the fourth and fifth quintiles (p = 0.049) and 50% lower with baseline FT4 levels in the first quintile (p = 0.046). No association between TSH and the outcome was found.

CONCLUSIONS

Higher and lower FT4 levels were, respectively, a risk and a protective factor for the decline in functional status in a cohort of euthyroid older adults at risk of frailty.

Expert consensus on diagnosis and treatment for elderly with thyroid diseases in China (2021)

In order to improve the diagnosis and treatment of senile thyroid diseases in China and to promote healthy aging, the Endocrine Metabolic Diseases Group of the Chinese Geriatrics Society, and the Thyroid Group of the Chinese Society of Endocrinology jointly drafted the "Expert consensus on diagnosis and treatment for Chinese elderly with thyroid diseases" (referred to as consensus). The Consensus consists of five parts that set 40 recommendations on main clinical issues. The consensus emphasizes clinical focus on the age-related changes of the hypothalamus-pituitary-thyroid axis in the elderly, and it recommends application of comprehensive geriatric assessment to thoroughly evaluate the impact of thyroid diseases and relevant intervention on overall health condition. Meanwhile, it recommends generalization of screening for hypothyroidism during admission to nursing institution or hospital, and routine health check-ups. Furthermore, it develops individualized stratified management on hyperthyroidism, hypothyroidism, thyroid nodules, and differentiated thyroid carcinoma in the elderly distinguished from the youngers, including treatment regimen, control ranges, and flowcharts for diagnosis and treatment. The Consensus will provide the basis for clinical decisions and health management of thyroid diseases in the elderly by geriatrician, endocrinologist, and general practitioners.

Low TSH Is Associated With Frailty in an Older Veteran Population Independent of Other Thyroid Function Tests

Low TSH is associated with frailty in the older adult. We studied whether low TSH is an independent marker of frailty or is an indicator of subclinical hyperthyroidism, which in turn predicts frailty. Of outpatient veterans seen between January 2005 and December 2016, we identified 100 patients aged ≥60 years with two low TSH (<0.5 µIU/ml) and one fT3 measurement and 50 matched controls (TSH 0.5–5.0 µIU/ml). We used a deficit accumulation approach to create a frailty index (FI). The higher the FI, the more likely (p<0.001) that patients had expired. Patients with low (0.31 ± 0.11 µIU/mL) versus normal (1.84 ± 0.84 µIU/mL) TSH had higher mean FI compared to controls (0.25 ± 0.12 vs. 0.15 ± 0.07, p < .001). Low TSH was significantly associated with frailty (p < .001), independent of age. However, lower TSH was not associated with higher fT3 or fT4 levels. There was a nonsignificant inverse association of fT3 levels with FI (p = .13), which disappeared when adjusted for age. Similar to prior studies, low TSH was associated with frailty. However, neither fT3 nor fT4 predicted low TSH or FI, suggesting that the association of low TSH with frailty is not due to subclinical hyperthyroidism, but perhaps to effects of comorbidities on TSH secretion.

Different Relationships Between Thyrotropin and Muscle Strength According to Sex and Age in Euthyroid Koreans (The 6th Korea National Health and Nutritional Examination Survey 2014-2015)

Background: Changes in muscle mass and strength can be caused by multiple endocrine factors, including thyroid dysfunction. However, the relationship between thyroid function and muscle strength in euthyroid individuals is not clear. In the present study, we investigated the relationship between thyroid function and handgrip strength (HGS) in euthyroid Koreans, especially according to sex and age. Methods: This was a population-based, cross-sectional study from the 6th Korea National Health and Nutrition Examination Survey including 2894 Koreans (1487 men and 1407 women) aged ≥19 years. Serum thyrotropin (TSH) and free thyroxine (fT4) levels were measured. HGS was measured using a digital grip strength dynamometer. Results: Serum TSH level, but not serum fT4 level, was significantly associated with HGS in men, but neither TSH nor fT4 level was associated with HGS in women. Serum TSH showed a negative association with HGS in men aged <65 years (n = 1376; β = -0.566, p = 0.008), but a positive association in men aged ≥65 years (n = 111; β = 1.158, p = 0.010) after adjusting for confounders. HGS decreased as TSH tertile increased in men aged <65 years (p for trend = 0.010), but increased with TSH tertile in men aged ≥65 years (p for trend = 0.009) after adjusting for confounders. Odds ratios (ORs) for the lowest quartile of HGS increased in the highest tertile of TSH among men aged <65 years (OR = 1.657 [95% confidence interval {CI} 1.099-2.500], p = 0.006) and decreased in the highest tertile of TSH among men aged ≥65 years (OR = 0.176 [CI 0.032-0.966], p = 0.034) after adjusting for confounders. Conclusions: In euthyroid Koreans, serum TSH levels were significantly associated with HGS only in men and this relationship was found to depend significantly on age. These findings suggest that age has a distinct influence on the effect of even subtle change of thyroid function on muscle strength in men.

Clinical Parameters Are More Likely to Be Associated with Thyroid Hormone Levels than with Thyrotropin Levels: A Systematic Review and Meta-Analysis

Background: Though the functional states of other endocrine systems are not defined on the basis of levels of controlling hormones, the assessment of thyroid function is based on levels of the controlling hormone thyrotropin (TSH). We, therefore, addressed the question as to whether levels of thyroid hormones [free thyroxine (fT4), total triiodothyronine (TT3)/free triiodothyronine (fT3)], or TSH levels, within and beyond the reference ranges, provide the better guide to the range of clinical parameters associated with thyroid status. Methods: A PubMed/MEDLINE search of studies up to October 2019, examining associations of levels of thyroid hormones and TSH, taken simultaneously in the same individuals, with clinical parameters was performed. We analyzed atrial fibrillation, other cardiac parameters, osteoporosis and fracture, cancer, dementia, frailty, mortality, features of the metabolic syndrome, and pregnancy outcomes. Studies were assessed for quality by using a modified Newcastle-Ottawa score. Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines were followed. A meta-analysis of the associations was performed to determine the relative likelihood of fT4, TT3/fT3, and TSH levels that are associated with the clinical parameters. Results: We identified 58 suitable articles and a total of 1880 associations. In general, clinical parameters were associated with thyroid hormone levels significantly more often than with TSH levels-the converse was not true for any of the clinical parameters. In the 1880 considered associations, fT4 levels were significantly associated with clinical parameters in 50% of analyses. The respective frequencies for TT3/fT3 and TSH levels were 53% and 23% (p < 0.0001 for both fT4 and TT3/fT3 vs. TSH). The fT4 and TT3/fT3 levels were comparably associated with clinical parameters (p = 0.71). More sophisticated statistical analyses, however, indicated that the associations with TT3/fT3 were not as robust as the associations with fT4. Conclusions: Thyroid hormones levels, and in particular fT4 levels, seem to have stronger associations with clinical parameters than do TSH levels. Associations of clinical parameters with TSH levels can be explained by the strong negative population correlation between thyroid hormones and TSH. Clinical and research components of thyroidology currently based on the measurement of the thyroid state by reference to TSH levels warrant reconsideration.

Low free triiodothyronine levels are associated with risk of frailty in older adults with type 2 diabetes mellitus

OBJECTIVES

With aging populations around the world, frailty is becoming more prevalent increasing the need to early identify those at risk of frailty. The association between thyroid hormone levels and frailty in subjects with type 2 diabetes mellitus (T2DM) remains unclear. The objective of the study was to evaluate the relationship between thyroid hormone concentrations and frailty in older adults with T2DM.

METHODS

A total of 240 older adults with T2DM were divided into three groups according to the frailty phenotype criteria: robust group (n = 94), pre-frail (n = 110) and frail group (n = 36). Concentrations of free triiodothyronine (FT3), free thyroxine (FT4) and thyroid-stimulating hormone (TSH), 25-hydroxyvitamin D₃ [25(OH) D₃], highly sensitive C-reactive protein (hs-CRP) and interleukin-6 (IL-6) were determined. Handgrip strength was measured using a Jamar hand dynamometer. Physical function was assessed by gait speed and the timed go and up (TUG) test. Logistic regression analysis was performed to evaluate the association between FT3 and frailty.

RESULTS

The FT3 level was the lowest among frail people (2.56 ± 0.42 pg/mL), followed by pre-frail participants (2.73 ± 0.38 pg/mL), with the highest among the robust subjects (2.83 ± 0.43 pg/mL). FT3 level was positively correlated with handgrip strength and gait speed (R = 0.313, P < 0.001; R = 0.250, P < 0.001, respectively), while negatively correlated with TUG time (R = -0.276, P < 0.001). After adjusting for age, sex, TSH, 25(OH) D₃ and estimate glomerular filtration rate (eGFR), logistic regression showed that low FT3 was significantly associated with an increased risk of frailty (odds ratio (OR): 4.53; 95% confidence interval (CI): 1.89-10.83; P = 0.001).

CONCLUSION

Low levels of FT3 were associated with an increased risk of frailty in older adults with T2DM. Measuring FT3 might be useful for identifying those at high risk of frailty.

[The thyroid gland in old age : Physiology and pathology]

In healthy older people the metabolism of thyroid hormones is physiologically altered and can possibly even actively contribute to longevity. This should also be taken into consideration in the treatment of diseases of the thyroid and principally also for younger patients. For example, with progressing age comorbidities become more prevalent and especially in cardiovascular diseases, hyperthyroidism is less well tolerated, and should be treated more aggressively. Benign multinodular goiter also becomes more prevalent in old age and should be surgically treated when causing mechanical symptoms. The treatment concept for malignant diseases should be adapted to the holistic situation of the patient but principally in the same manner as in younger patients. Old and very old patients also benefit from adequate, risk-adapted treatment of thyroid gland diseases so that appropriate diagnostics and clarification are meaningful, regardless of age.

Thyroid hormones and frailty in persons experiencing extreme longevity

CONTEXT

The aging phenotype is quite heterogeneous, being the result of the capability of each individual to successfully or unsuccessfully response to stressors. The reduction of homeostatic reserve characterizing aging is accompanied by a remodeling of the endocrine system. Frailty has been indicated as a promising way for capturing the physiological decline as well as the biological aging of the individuals. In particular, the Frailty Index (FI), based on the assumption that health deficits tend to accumulate with aging, represents a quantitative measure of extreme interest.

OBJECTIVE

The study aims to correlate the thyroid hormone levels with FI in a population of centenarians and their offspring to capture the effects of thyroid remodeling in extreme longevity.

STUDY DESIGN

The study described 593 well-characterized Italian subjects, including 180 centenarians, as well as 276 centenarian's offspring and 137 age-matched controls.

RESULTS

FT3 levels and FT3/FT4 ratio were significantly lower (p < 0.001) and TSH levels higher (p < 0.001) in centenarians compared to the other groups, analysing both overall subjects and excluding subjects with hormone levels out of the normal ranges. In overall centenarians, we observed a negative correlation between FI and FT3 (ρ: -0.281, p < 0.001), FT3/FT4 (ρ: -0.344, p < 0.001) and TSH (ρ: -0.223, p 0.003) and a positive association between FI and FT4 (ρ: 0.189, p = 0.001). In centenarians with hormone levels within the normal ranges, similar negative correlations were observed between FI and FT3 (ρ: -0.201, p = 0.02) and FT3/FT4 (ρ: -0.264, p = 0.002). In this sub-analysis, FI positively correlated with FT4 and age (ρ: 0.167, p = 0.05; ρ: 0.219, p = 0.005, respectively). Conversely, no significant correlations were observed between hormone levels and FI in offspring and controls.

CONCLUSIONS

We found an association between thyroid hormone levels and frailty in centenarians, underlying the significant role of thyroid in the aging process and longevity.

Objectives, design and main findings until 2020 from the Rotterdam Study

The Rotterdam Study is an ongoing prospective cohort study that started in 1990 in the city of Rotterdam, The Netherlands. The study aims to unravel etiology, preclinical course, natural history and potential targets for intervention for chronic diseases in mid-life and late-life. The study focuses on cardiovascular, endocrine, hepatic, neurological, ophthalmic, psychiatric, dermatological, otolaryngological, locomotor, and respiratory diseases. As of 2008, 14,926 subjects aged 45 years or over comprise the Rotterdam Study cohort. Since 2016, the cohort is being expanded by persons aged 40 years and over. The findings of the Rotterdam Study have been presented in over 1700 research articles and reports. This article provides an update on the rationale and design of the study. It also presents a summary of the major findings from the preceding 3 years and outlines developments for the coming period.

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.

Individualised requirements for optimum treatment of hypothyroidism: complex needs, limited options

Levothyroxine (LT4) therapy has a long history, a well-defined pharmacological profile and a favourable safety record in the alleviation of hypothyroidism. However, questions remain in defining the threshold for the requirement of treatment in patients with subclinical hypothyroidism, assessing the dose adequacy of the drug, and selecting the best treatment mode (LT4 monotherapy versus liothyronine [LT3]/LT4 combinations) for subpopulations with persisting complaints. Supplied as a prodrug, LT4 is enzymatically converted into the biologically more active thyroid hormone, triiodothyronine (T3). Importantly, tetraiodothyronine (T4) to T3 conversion efficiency may be impaired in patients receiving LT4, resulting in a loss of thyroid-stimulating hormone (TSH)-mediated feed-forward control of T3, alteration of the interlocking equilibria between serum concentrations of TSH, free thyroxine (FT4), and free triiodothyonine (FT3), and a decrease in FT3 to FT4 ratios. This downgrades the value of the TSH reference system derived in thyroid health for guiding the replacement dose in the treatment situation. Individualised conditionally defined setpoints may therefore provide appropriate biochemical targets to be clinically tested, together with a stronger focus on clinical presentation and future endpoint markers of tissue thyroid state. This cautionary note encompasses the use of aggregated statistical data from clinical trials which are not safely applicable to the individual level of patient care under these circumstances.

Trends, Determinants, and Associations of Treated Hypothyroidism in the United Kingdom, 2005-2014

BACKGROUND

Recent reports suggest that prescriptions for thyroid hormones have increased. Recent trends in and determinants of the prevalence of treated hypothyroidism across the United Kingdom were therefore analyzed.

METHODS

Data covering the whole of the United Kingdom held by the National Health Service and the Office of National Statistics were examined. The main outcome measured was trends in the prevalence of treated hypothyroidism between 2005 and 2014. In addition, linear trend forecasting was performed to estimate projected trends in the prevalence of treated hypothyroidism up to the year 2025. Furthermore, determinants of variation of treated hypothyroidism prevalence across each of the 237 health areas in the United Kingdom in 2014 and its association with other health conditions were explored by multivariate linear regression analyses.

RESULTS

The prevalence of treated hypothyroidism increased from 2.3% (1.4 million) to 3.5% (2.2 million) of the total British population between the years 2005 and 2014 and is projected to rise further to 4.2% (2.9 million) by 2025. There was large geographical variation of treated hypothyroidism across the United Kingdom, with London having the lowest (1.4%) and the Western Isles of Scotland having the highest (6.3%) prevalence. This variation was attenuated, but did not completely disappear, after some potential determinants were accounted for. The prevalence of treated hypothyroidism was independently related to health areas, with a higher proportion of individuals who were female, white, and obese, and negatively associated with prevalent cigarette smoking. The prevalence of treated hypothyroidism was significantly associated with the frequency of prevalent atrial fibrillation but not with other major health conditions, including ischemic heart disease and osteoporosis.

CONCLUSIONS

Between 2005 and 2014, the prevalence of treated hypothyroidism increased across the United Kingdom, has wide geographical variation, and is likely to increase further for the foreseeable future. Clinical effects and cost-effectiveness of the trend in increasing treatment of hypothyroidism remains to be evaluated.

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.

Clinical aspects of thyroid function during ageing

Globally, populations are ageing at a rapid rate. The increase in the number of older citizens is accompanied by an increased prevalence of thyroid dysfunction, one of the most common disorders in older people. However, the diagnosis of thyroid dysfunction in older people is hindered by several factors, including the scarcity of thyroid dysfunction symptoms in older people. We describe the physiological changes in thyroid function that occur with increasing age, focusing on literature regarding changes in thyroid function test results in older populations. We also discuss treatment considerations for clinical and subclinical thyroid dysfunction according to international guidelines for older people. Finally, we discuss the relationship between variations in thyroid function and common diseases of old age including cardiovascular disease, osteoporosis, cognitive impairment, and frailty and suggest directions for future research.

The physiology of endocrine systems with ageing

During ageing, the secretory patterns of the hormones produced by the hypothalamic-pituitary axis change, as does the sensitivity of the axis to negative feedback by end hormones. Additionally, glucose homoeostasis tends towards disequilibrium with increasing age. Along with these endocrine alterations, a loss of bone and muscle mass and strength occurs, coupled with an increase in fat mass. In addition, ageing-induced effects are difficult to disentangle from the influence of other factors that are common in older people, such as chronic diseases, inflammation, and low nutritional status, all of which can also affect endocrine systems. Traditionally, the decrease in hormone activity during the ageing process has been considered to be detrimental because of the related decline in bodily functions. The concept of hormone replacement therapy was suggested as a therapeutic intervention to stop or reverse this decline. However, clearly some of these changes are a beneficial adaptation to ageing, whereas hormonal intervention often causes important adverse effects. In this paper, we discuss the effects of age on the different hypothalamic-pituitary-hormonal organ axes, as well as age-related changes in calcium and bone metabolism and glucose homoeostasis.

Degree of Peripheral Thyroxin Deiodination, Frailty, and Long-Term Survival in Hospitalized Older Patients

CONTEXT

Although the association between low free triiodothyronine (FT3) and poor outcome has been extensively reported in literature, the degree of peripheral thyroxin deiodination and its relationship with frailty and survival in hospitalized older patients has not yet been fully established. The aim of the current study was to evaluate the possible correlation between FT3/free thyroxine (FT4) ratio reduction, an indirect marker of thyroxin deiodination impairment, and frailty status and survival in hospitalized older patients.

METHODS

We consecutively enrolled older patients, hospitalized in the geriatrics ward of the University of Pisa. At admission, Multidimensional Geriatric Assessment (MGA) and Multi Prognostic Index (MPI), an indirect measure of frailty, were obtained from all the patients. Causes of hospitalization and prevalence of delirium were recorded. Blood samples for FT3, FT4, and thyrotropin value evaluation were drawn after an overnight fast.

RESULTS

A total of 643 patients (83.8 ± 7.4 years, 53% women) were studied. FT3 was inversely and strongly correlated, whereas FT4 was moderately positively correlated with MGA parameters, MPI score (P < 0.001 and P < 0.05, respectively), and survival (P < 0.001 and P = 0.09, respectively). FT3/FT4 ratio reduction was highly associated with worse MGA (P < 0.001) and MPI scores (P < 0.0001), even in patients without low FT3. The inclusion of FT3 in the final model of multivariate Cox regression confirmed the independent role of FT3/FT4 ratio in predicting survival (P = 0.005).

CONCLUSION

Overall, our study documented a strong association between FT3/FT4 ratio reduction, a surrogate marker of peripheral thyroxin deiodination, and frailty. Moreover, FT3/FT4 ratio value emerged as independent marker of survival, even in patients with normal FT3 values.