Endogenous and Exogenous Thyrotoxicosis and Risk of Incident Cognitive Disorders in Older Adults

Considerations in the Diagnosis and Management of Thyroid Dysfunction in Older Adults

Background: Thyroid dysfunction is common in older adults and poses diagnostic and management challenges for clinicians. In this narrative review, we present published data focusing on special considerations in the diagnosis and management of hypothyroidism and hyperthyroidism in older adults. Methods: A comprehensive literature search of the PubMed and Ovid MEDLINE databases was conducted from January 2000 to December 2024 to identify pertinent articles in English for this narrative review. Results: Due to significant cardiovascular risk if untreated, both overt hypothyroidism and hyperthyroidism should be treated in older adults. Findings from observational studies do not support treating older adults with subclinical hypothyroidism with a thyrotropin (TSH) <7 mIU/L. However, observational data have demonstrated an increased risk of cardiovascular mortality and stroke in older adults with subclinical hypothyroidism with TSH 7.0-9.9 mIU/L and of coronary heart disease, cardiovascular mortality, and heart failure in those with TSH ≥10 mIU/L, suggesting levothyroxine treatment in these individuals should be considered. Data from clinical trials failed to show improvement with levothyroxine in hypothyroidism symptoms or fatigue in older adults with subclinical hypothyroidism compared with placebo. Over- and under-replacement with thyroid hormone is common and should be avoided, as population-based studies have shown associations with adverse cardiovascular and skeletal events. Subclinical hyperthyroidism with a TSH <0.1 mIU/L should be treated in older individuals as it has been associated with increased cardiovascular risk and bone density loss based on observational data. Randomized controlled trials have shown that long-term low-dose methimazole is a viable alternative to radioactive iodine in older adults with hyperthyroidism. Conclusions: A personalized approach should be undertaken in the diagnosis and management of thyroid dysfunction in older adults. Multiple factors should be considered, including physiological age-related changes in thyroid function, comorbidities, and polypharmacy. Care should be taken to maintain euthyroidism in order to avoid adverse events.

Sex Differences in Risk for Iatrogenic Thyrotoxicosis Among Older Adults: An Analysis from Real-World Clinical Data

Background: Overtreatment with thyroid hormone is common and is associated with multiple adverse health outcomes, especially in older adults. Higher overtreatment rates have been reported among women. Understanding this sex difference could lead to better clinical utilization of therapy in at-risk populations. Methods: We performed a retrospective cohort study to examine the relationship between iatrogenic thyrotoxicosis and patient sex, adjusting for demographics, comorbidities, body composition, and thyroid hormone dosing using electronic health records for adults age 50 and older in a large community health system in the United States. Results: A total of 20,724 patients met all inclusion criteria, of whom 77% were female and 23% non-White. Women were more likely to have a low thyrotropin (TSH) compared to men (36.7% vs. 23.9%; unadjusted hazard ratio [HR] = 1.67 [95% confidence interval {CI} 1.56-1.79]). Many covariates varied by sex, including rates of several comorbidities, and there was a small but statistically significant difference in the median daily levothyroxine dose per actual body mass: 1.1 μg/kg in male patients compared with 1.2 μg/kg in female patients (p < 0.001). Adjusting for covariates other than dose did not significantly change the sex-related risk of iatrogenic thyrotoxicosis. In fully adjusted Cox models including dose per actual body mass, the female versus male HR = 1.50 [CI 1.34-1.69] was also not different from models which did not account for dose (p = 0.422). However, the association between female sex and thyrotoxicosis risk was partially mediated when adjusting for dose per ideal body mass (HR = 1.30 [CI: 1.16-1.46]; p < 0.001) and was fully mediated by dose calculated using lean body mass (HR = 1.06 [CI: 0.95-1.19]; p < 0.001). That is, women had higher risk of iatrogenic thyrotoxicosis compared to men receiving similar actual body mass doses, whereas women and men receiving comparable lean body mass doses had comparable risk. Conclusions: Mediation analysis demonstrates that the increased risk of iatrogenic thyrotoxicosis in older women may be attributable to differences in body composition between men and women. The use of ideal or lean body weight-based dose calculators in place of actual body weight dosing could reduce this potential source of iatrogenic thyrotoxicosis risk in older women.

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

BACKGROUND

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Association Between Serum Thyrotropin and Cancer Recurrence in Differentiated Thyroid Cancer: A Population-Based Retrospective Cohort Study

Background: Levothyroxine to suppress thyrotropin (TSH) to <0.5 mIU/L following thyroidectomy in differentiated thyroid cancer (DTC) may reduce recurrence in higher-risk DTC. However, there is limited evidence to support guideline recommendations to maintain TSH in the low-normal range of 0.5-2 mIU/L to reduce recurrence in patients with lower risk DTC. The primary objective was to assess the association between exposure to high normal serum TSH (2-4 mIU/L) as compared with low normal TSH (0.5-2 mIU/L) target ranges and cancer recurrence in patients with DTC after thyroidectomy. Methods: This population-based retrospective cohort study used linked, administrative health care databases from Ontario, Canada, to follow patients with DTC post-thyroidectomy from 2007 to 2018. The exposure was time updated, serum TSH, treated as a cumulative and instantaneous exposure. Multivariable cause-specific proportional hazard regression analyses were performed to determine time to DTC recurrence from index date, defined as a composite of repeat neck surgery, radioactive iodine (RAI) treatment, and/or DTC-specific death. Results were also stratified by initial treatment as a marker of baseline recurrence risk in a sensitivity analysis. Results: This cohort of 26,336 individuals (78% female) with DTC and a median age of 50 years were followed for a median of 5.9 (interquartile range 3.6-8.6) years; 40.9% were initially treated with a hemi-thyroidectomy only and 38.2% received a total thyroidectomy and RAI. Compared with exposure to TSH 0.5 to ≤2 mIU/L, DTC recurrence rate was similar for each additional 3 months of exposure to TSH >2 to ≤4 mIU/L (adjusted cause specific [cs] hazard ratio [HR] 0.99 [confidence interval or CI 0.97-1.02]) but was significantly increased with each additional 3 months of exposure to TSH >4 mIU/L (adjusted csHR 1.07 [CI 1.04-1.09]). Results were similar across baseline treatment groups. Conclusion: There was no difference in clinically significant recurrence in those with low-risk DTC maintained with a TSH of 0.5-2 mIU/L compared with 2-4 mIU/L. Guidelines should consider liberalizing target TSH level post thyroidectomy in low-risk cohorts. These results cannot be applied to patients with high-risk DTC.

Exploring the Link Between Exogenous Thyroid Hormones and Dementia Symptoms: A Real-World Disproportionality Analysis of FDA Adverse Event Reporting System

BACKGROUND

A growing body of evidence indicates a strong association between exogenous thyroid hormone (ETH) and brain health. Establishing the potential relationship between ETH therapy and dementia symptoms is crucial for patients with thyroid disorders.

OBJECTIVE

In this study, we investigate the potential association between ETH therapy and dementia symptoms by exploring the Food and Drug Administration Adverse Event Reporting System (FAERS) database.

METHODS

Disproportionality analysis (DPA) was conducted using postmarketing data from the FAERS repository (Q1 2004 to Q4 2023). Cases of dementia symptoms associated with ETH therapy were identified and analyzed through DPA using reporting odds ratios and information component methods. Dose and time-to-onset analyses were performed to assess the association between ETH therapy and dementia symptoms.

RESULTS

A total of 9889 cases of ETH-associated symptoms were identified in the FAERS database. Dementia accounted for a consistent proportion of adverse drug reactions each year (3.4%-6.3%). The DPA indicated an association between ETH therapy and dementia symptoms, which remained significant even across sex, age, and indications. The median time-to-onset of dementia symptoms was 7.5 days, and the median treatment time was 40.5 days. No significant dose-response relationship was observed.

CONCLUSION AND RELEVANCE

This study provides evidence for a link between ETH therapy and dementia. Clinicians are therefore advised to exercise vigilance, conduct comprehensive monitoring, and consider individualized dosing to mitigate potential reactions to ETH drug administration.

Thyroid hormones for euthyroid patients with simple goiter growing over time: a survey of European thyroid specialists

BACKGROUND

Treatment of simple goiter (SG) growing over time with thyroid hormone (TH) therapy is discouraged by international guidelines.

PURPOSE

To ascertain views of European thyroid specialists about TH treatment for euthyroid patients with growing SG and explore associations with management choice.

METHODS

Online survey on the use of TH for growing SG among thyroid experts from 28 European countries.

RESULTS

The response rate was 31.5% (5430/17,247). Most respondents were endocrinologists. Twenty-eight percent asserted that TH therapy may be indicated in euthyroid patients with a growing SG. National and regional differences were noted, from 7% of positive responses in The Netherlands to 78% in Czech Republic (p < 0.0001). TH was more frequently prescribed by respondents over 40 years old (OR 1.77, 2.13, 2.41 if 41-50, 51-60, >60, respectively), and working in areas of former iodine insufficiency (OR 1.24, 95% CI 1.03-1.50). TH was less frequently prescribed by endocrinologists (OR 0.77, 95% CI 0.62-0.94) and respondents working in Southern Europe (OR 0.40, 95% CI 0.33-0.48), Northern Europe (OR 0.28, 95% CI 0.22-0.36) and Western Asia (OR 0.16, 95% CI 0.11-0.24) compared to Western Europe. Associations with respondents' sex, country, availability of national thyroid guidelines, and gross national income per capita were absent or weak.

CONCLUSIONS

Almost a third of European thyroid specialists support treating SG with TH, contrary to current guidelines and recommendations. This calls for urgent attention.

Managing thyroid hormone replacement after total thyroidectomy: Guidance for family medicine

Thyroid hormones are among the most prescribed medications to patients worldwide and are commonly used to treat hypothyroidism. Thyroxine is also indicated after total thyroidectomy for Graves' disease or a multinodular goitre. In this commentary, we discuss and provide guidance for family medicine and primary care clinicians on how to navigate thyroid hormone replacement in patients after total thyroidectomy for cancer.

The triglyceride-glucose index and risk of cognitive impairment: a systematic review and meta-analysis with inclusion of two national databases

Background

To investigate the relationship between the triglyceride and glucose (TyG) index and cognitive impairment (CI).

Methods

Five authoritative databases were systematically searched for potentially relevant studies on 'TyG index' and 'CI' from inception to 27 April 2024. Two representative databases from the United Kingdom and United States were also included. We used the PICOS criteria to select available articles. All data was combined to compute Odd Ratios (ORs).

Results

15 studies were included in the meta-analysis (participants: 5604303). The pooled effect sizes demonstrate that individuals with a high TyG index exhibit a significantly elevated risk of CI compared to those with a low TyG index (OR = 2.16, 95%CI: 1.51; 3.08, p < 0.001). The subgroup analysis showed that inpatients with a high TyG index exhibited an increased risk of CI (OR = 4.56, 95%CI: 3.09; 6.74, p < 0.001). Furthermore, the risk of developing distinct types of CI differed significantly [CI: OR = 1.64, 95% CI: 1.29; 2.07, p < 0.001; Vascular Cognitive Impairment (VCI): OR = 5.39, 95% CI: 3.33; 8.70, p < 0.001].

Conclusion

A positive correlation exists between the TyG index and risk of CI, which has potential value in optimizing CI risk stratification among elderly people, especially those hospitalized.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42023450336.

Thyroid Function and Cognitive Decline: A Narrative Review

OBJECTIVE

As the population of older adults in the United States continues to rise, understanding modifiable risk factors that contribute to cognitive decline and dementia becomes increasingly important. This narrative review summarizes existing literature on the association between thyroid function in the euthyroid range, hypothyroidism and hyperthyroidism, and cognitive outcomes in older adults.

METHODS

A comprehensive literature search of the PubMed and Ovid/Medline databases was conducted. Randomized controlled trials, systematic reviews, meta-analyses, and observational studies published in English between January 2000 and December 2023 were included.

RESULTS

Overall, existing studies yielded conflicting results, failing to delineate a concrete relationship between thyroid function and cognitive outcomes and/or dementia in older adults. There may be a possible association between higher thyroid stimulating hormone in the reference range and lower risk of incident dementia, which may be more pronounced in women. Majority of studies elucidated a possible association between low thyroid stimulating hormone and incident dementia, with suggestion that duration of hyperthyroidism may contribute to increasing dementia risk. Even though evidence on the association of hypothyroidism and cognitive decline are disparate, current data do not support treatment of subclinical hypothyroidism to improve cognitive outcomes in older adults.

CONCLUSION

Despite numerous studies, there is no conclusive evidence that supports a direct relationship between hyperthyroidism or hypothyroidism and cognitive decline. Study limitations include heterogeneity in study designs, measurement methodologies, and cognitive assessment tools. Future research is needed to better delineate whether an association exists and whether treatment of thyroid dysfunction ameliorates cognitive impairment.

View on Metformin: Antidiabetic and Pleiotropic Effects, Pharmacokinetics, Side Effects, and Sex-Related Differences

Metformin is a synthetic biguanide used as an antidiabetic drug in type 2 diabetes mellitus, achieved by studying the bioactive metabolites of Galega officinalis L. It is also used off-label for various other diseases, such as subclinical diabetes, obesity, polycystic ovary syndrome, etc. In addition, metformin is proposed as an add-on therapy for several conditions, including autoimmune diseases, neurodegenerative diseases, and cancer. Although metformin has been used for many decades, it is still the subject of many pharmacodynamic and pharmacokinetic studies in light of its extensive use. Metformin acts at the mitochondrial level by inhibiting the respiratory chain, thus increasing the AMP/ATP ratio and, subsequently, activating the AMP-activated protein kinase. However, several other mechanisms have been proposed, including binding to presenilin enhancer 2, increasing GLP1 release, and modification of microRNA expression. Regarding its pharmacokinetics, after oral administration, metformin is absorbed, distributed, and eliminated, mainly through the renal route, using transporters for cationic solutes, since it exists as an ionic molecule at physiological pH. In this review, particular consideration has been paid to literature data from the last 10 years, deepening the study of clinical trials inherent to new uses of metformin, the differences in effectiveness and safety observed between the sexes, and the unwanted side effects. For this last objective, metformin safety was also evaluated using both VigiBase and EudraVigilance, respectively, the WHO and European databases of the reported adverse drug reactions, to assess the extent of metformin side effects in real-life use.