Statin Initiation and Risk of Incident Alzheimer Disease and Cognitive Decline in Genetically Susceptible Older Adults.

BACKGROUND AND OBJECTIVES: The association of statin initiation with incident Alzheimer disease (AD) dementia and cognitive decline by the APOE ε4 allele is unknown. Our objective was to examine whether the association of statin initiation with incident AD dementia and cognitive decline differs by the APOE ε4 allele. METHODS: This population-based longitudinal cohort study was conducted in 4 urban communities in Chicago, IL, United States, consisting of 4,807 participants. Statin initiation is based on the inspection of medications during home assessments. Clinical diagnosis for incident AD used the NINCDS-ADRDA criteria, and longitudinal measurements of global cognition consisted of episodic memory, perceptual speed, and the Mini-Mental State Examination tests. RESULTS: The study participants had a mean age of 72 years, consisting of 63% female individuals and 61% non-Hispanic Black individuals. During the study period, 1,470 (31%) participants reported statin initiation. In a covariate-adjusted competing risk model, statin initiation was associated with a reduced risk of incident clinical AD [hazard ratio (HR) 0.81 (95% CI 0.70-0.94)] compared with nonusers. This association was statistically significantly lower (p interaction = 0.015) among participants with the APOE ε4 allele [HR 0.60 (95% CI 0.49-0.74)] compared with those without the APOE ε4 allele [HR 0.96 (95% CI 0.82-1.12)]. The annual decline in global cognition (ß = 0.021, 95% CI 0.007-0.034) and episodic memory (ß = 0.020, 95% CI 0.007-0.033) was also substantially slower among participants with the APOE ε4 allele after statin initiation compared with nonusers. However, the association of statin initiation with cognitive decline was not significant among those without the APOE ε4 allele. DISCUSSION: Our findings suggest that statins might be associated with a lower risk of incident AD among individuals with the APOE ε4 allele. The benefits of statin therapy need further consideration in randomized clinical trials, especially among those with the APOE ε4 allele. CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that among those aged 65 years or older, statin initiation was associated with a reduced risk of Alzheimer disease, especially in the presence of an APOE-e4 allele.

Hyperthyroidism Due to Graves Disease After Radiofrequency Ablation.

Management options for benign, autonomously functioning, and malignant thyroid nodules were limited to surgery or targeting by radioactive iodine before the availability of radiofrequency ablation (RFA). Despite being a relatively new technique, RFA may be favored for patients of high surgical risk, and for those who wish to avoid hypothyroidism. Although insurance coverage for the procedure can be a significant barrier, several groups of investigators have shown improved quality of life for RFA compared to surgery, due to the less invasive nature and favorable risk profile. Hyperthyroidism due to transient thyroiditis is a known risk of RFA, secondary to direct trauma and subsequent thyroid hormone release. Here we present a case of an adult with large, symptomatic, multinodular goiter, with no prior history of thyroid autoimmunity, who underwent RFA with successful volume reduction of two nodules, but who developed acute hyperthyroidism due to Graves disease eight weeks after RFA. Larger studies evaluating the risks of RFA should evaluate for incident hyperthyroidism, specifically for Graves disease/thyroid autoimmunity, as this could represent an additional risk of the procedure.

Critical Approach to Hypothyroid Patients With Persistent Symptoms.

Hypothyroidism is a common condition, and numerous studies have been published over the last decade to assess the potential risks associated with this disorder when inappropriately treated. The standard of care for treatment of hypothyroidism remains levothyroxine (LT4) at doses to achieve biochemical and clinical euthyroidism. However, about 15% of hypothyroid patients experience residual hypothyroid symptoms. Some population-based studies and international population-based surveys have confirmed dissatisfaction with LT4 treatment in some hypothyroid patients. It is well established that hypothyroid patients treated with LT4 exhibit higher serum thyroxine:triiodothyronine ratios and can have a persistent increase in cardiovascular risk factors. Moreover, variants in deiodinases and thyroid hormone transporter genes have been associated with subnormal T3 concentrations, persistent symptoms in LT4-treated patients, and improvement in response to the addition of liothyronine to LT4 therapy. The American (ATA) and European Thyroid Association (ETA) guidelines have recently evolved in their recognition of the potential limitations of LT4. This shift is reflected in prescribing patterns: Physicians' use of combination therapy is prevalent and possibly increasing. Randomized clinical trials have recently been published and, while they have found no improvement in treating hypothyroid patients, a number of important limitations did not allow generalizability. Meta-analyses have reported a preference rate for combination therapy in 46.2% hypothyroid patients treated with LT4. To promote discussions about an optimal study design, the ATA, ETA, and British Thyroid Association have recently published a consensus document. Our study provides a useful counterpoint on the controversial benefits of treating hypothyroid patients with combination therapy.

Longitudinal Changes in Blood Biomarkers of Clinical Alzheimer Disease in a Biracial Population Sample.

BACKGROUND AND OBJECTIVES: Recent studies suggest the utility of blood biomarkers in detecting changes in neurodegenerative disorders. The objective of our research was to test the hypothesis that the longitudinal changes in total tau (t-tau), neurofilament light chain (Nf-L), and glial fibrillary acidic protein (GFAP) are associated with structural MRI and the development of clinical Alzheimer disease (AD) and cognitive decline. METHODS: Data came from a population-based sample with serum concentrations of t-tau, Nf-L, and GFAP and cognitive characteristics measured over 17 years. The inclusion criteria for this investigation were based on participants with blood samples, cognitive function testing, and clinical diagnosis for AD. The longitudinal changes in the serum biomarkers were examined using linear mixed models for log10-transformed concentrations. RESULTS: In 1,327 participants (60% Black participants and 60% women, the concentration of t-tau increased annually by 4.8% (95% CI = 4.0-5.6) and Nf-L by 5.9% (95% CI = 5.4-6.4). The longitudinal change in GFAP was higher among Black participants than among White participants (4.4% vs 3.5% per year, p = 0.028). Baseline MRI characteristics were associated with the longitudinal changes in serum biomarkers of clinical AD. Specifically, a higher baseline third ventricular volume was associated with a higher rate of increase in the concentration of t-tau, and white matter hyperintensities predicted a higher rate of increase in Nf-L. The rate of change in concentrations of t-tau, Nf-L, and GFAP was significantly higher among those who developed clinical AD than in those with no cognitive impairment. For each standard deviation unit decline in global cognition, longitudinal change in t-tau increased by 81% (95% CI = 76-86), Nf-L by 113% (95% CI = 105-120), and GFAP by 66% (95% CI = 62-70). DISCUSSION: Blood biomarkers showed significant longitudinal changes corresponding to cognitive decline, clinical AD, and structural MRI characteristics. Our findings show that longitudinal changes in serum biomarkers were associated with several cognitive endophenotypes. CLASSIFICATION OF EVIDENCE: The study found Class II evidence that longitudinal changes in serum t-tau, Nf-L, and GFAP were associated with cognitive decline and the development of clinical AD in people older than 65 years.

Risk of Permanent Hypoparathyroidism Requiring Calcitriol Therapy in a Population-Based Cohort of Adults Older Than 65 Undergoing Total Thyroidectomy for Graves' Disease.

Objective: Total thyroidectomy for Graves' disease (GD) is associated with rapid treatment of hyperthyroidism and low recurrence rates. However, it carries the risk of surgical complications including permanent hypoparathyroidism, which contributes to long-term impaired quality of life. The objective of this study was to determine the incidence of permanent hypoparathyroidism requiring calcitriol therapy among a population-based cohort of older adults undergoing total thyroidectomy for GD in the United States. Methods: We performed a population-based cohort study using 100% Medicare claims from beneficiaries older than 65 years with GD who underwent total thyroidectomy from 2007 to 2017. We required continuous enrollment in Medicare Parts A, B, and D for 12 months before and after surgery to ensure access to comprehensive claims data. Patients were excluded if they had a preoperative diagnosis of thyroid cancer or were on long-term preoperative calcitriol. Our primary outcome was permanent hypoparathyroidism, which was identified based on persistent use of calcitriol between 6 and 12 months following thyroidectomy. We used multivariable logistic regression to identify characteristics associated with permanent hypoparathyroidism, including patient age, sex, race/ethnicity, neighborhood disadvantage, Charlson-Deyo Comorbidity Index, urban or rural residence, and frailty. Results: We identified 4650 patients who underwent total thyroidectomy for GD during the study period and met the inclusion criteria (mean age = 72.8 years [standard deviation = 5.5], 86% female, and 79% white). Among this surgical cohort, 104 (2.2% [95% confidence interval, CI = 1.8-2.7%]) patients developed permanent hypoparathyroidism requiring calcitriol therapy. Patients who developed permanent hypoparathyroidism were on average older (mean age 74.1 vs. 72.8 years) than those who did not develop permanent hypoparathyroidism (p = 0.04). On multivariable regression, older age was the only patient characteristic associated with permanent hypoparathyroidism (odds ratio age ≥76 years = 1.68 [CI = 1.13-2.51] compared with age 66-75 years). Conclusions: The risk of permanent hypoparathyroidism requiring calcitriol therapy among this national, U.S. population-based cohort of older adults with GD treated with total thyroidectomy was low, even when considering operations performed by a heterogeneous group of surgeons. These findings suggest that the risk of hypoparathyroidism should not be a deterrent to operative management for GD in older adults who are appropriate surgical candidates.

Examination of Neurofilament Light Chain Serum Concentrations, Physical Activity, and Cognitive Decline in Older Adults.

Importance: Little is known about the association of serum neurofilament light chain (NfL) concentrations and physical activity with the rate of cognitive decline in older adults. Objective: To examine the association of physical activity and NfL concentrations with cognitive decline in older adults over time. Design, Setting, and Participants: This cohort study used data from the Chicago Health and Aging Project (CHAP), a population-based cohort study that recruited participants through door-to-door census in 4 Chicago-area communities and collected data between 1993 and 2012 in cycles of 3 years. Participants in CHAP who had 2 or more cognitive function assessments and at least 1 blood sample collected for NfL measurement were selected for inclusion in the current study. Data were analyzed from January to December 2021. Exposures: Self-reported physical activity (minutes per week) and serum NfL concentration (pg/mL). Main Outcomes and Measures: Associations of baseline physical activity and NfL concentrations with changes in global cognitive function over time as evaluated using the East Boston Memory Test for episodic memory, the Symbol Digit Modalities Test for perceptual speed, and the Mini-Mental State Examination. Mixed-effects regression analyses were conducted to examine associations at baseline and longitudinally. Results: The study sample included 1158 participants (695 [60%] African American; 728 [63%] female), with a mean (SD) age of 77.4 (6.0) years and a mean educational level of 12.6 (3.5) years. Among participants with high NfL concentrations (>25 pg/mL), those who engaged in medium physical activity (<150 minutes per week) had a 12% slower rate of global cognitive decline (SD units, or ß, -0.065; 95% CI, -0.099 to -0.032) and participants who engaged in high physical activity (≥150 minutes per week) had a 36% slower rate of decline (ß, -0.048; 95% CI, -0.080 to -0.016) than did participants with low physical activity (no reported participation) (ß, -0.075; 95% CI, -0.108 to -0.041). For participants with low NfL concentrations (≤25 pg/mL), those who took part in medium physical activity had 43% slower global cognitive decline (ß, -0.025; 95% CI, -0.043 to -0.007) and individuals who participated in high physical activity had 30% slower decline (ß, -0.031; 95% CI, -0.048 to -0.014) than did those who participated in low physical activity (ß, -0.046; 95% CI, -0.066 to -0.025). Conclusions and Relevance: The findings suggest that physical activity is associated with diminished cognitive decline among older adults with increased serum NfL concentrations. The results support the potential use of blood biomarkers in measuring the benefits of health behaviors, such as physical activity, and early intervention for older adults at risk for cognitive decline.

Comparative Effectiveness of Levothyroxine, Desiccated Thyroid Extract, and Levothyroxine+Liothyronine in Hypothyroidism.

INTRODUCTION: Studies comparing levothyroxine (LT4) therapy with LT4 + liothyronine (LT3) or desiccated thyroid extract (DTE) did not detect consistent superiority of either treatment. Here, we investigated these therapies, focusing on the whole group of LT4-treated hypothyroid patients, while also exploring the most symptomatic patients. METHODOLOGY: Prospective, randomized, double-blind, crossover study of 75 hypothyroid patients randomly allocated to 1 of 3 treatment arms, LT4, LT4 + LT3, and DTE, for 22 weeks. The primary outcomes were posttreatment scores on the 36-point thyroid symptom questionnaire (TSQ-36), 12-point quality of life general health questionnaire (GHQ-12), the Wechsler memory scale-version IV (VMS-IV), and the Beck Depression Inventory (BDI). Secondary endpoints included treatment preference, biochemical and metabolic parameters, etiology of hypothyroidism, and Thr92Ala-DIO2 gene polymorphism. Analyses were performed with a linear mixed model using subject as a random factor and group as a fixed effect. RESULTS: Serum TSH remained within reference range across all treatment arms. There were no differences for primary and secondary outcomes, except for a minor increase in heart rate caused by DTE. Treatment preference was not different and there were no interferences of the etiology of hypothyroidism or Thr92Ala-DIO2 gene polymorphism in the outcomes. Subgroup analyses of the 1/3 most symptomatic patients on LT4 revealed strong preference for treatment containing T3, which improved performance on TSQ-36, GHQ-12, BDI, and visual memory index (VMS-IV component). CONCLUSIONS: As a group, outcomes were similar among hypothyroid patients taking DTE vs LT4 + T3 vs LT4. However, those patients that were most symptomatic on LT4 preferred and responded positively to therapy with LT4 + LT3 or DTE.

Population estimate of people with clinical Alzheimer's disease and mild cognitive impairment in the United States (2020-2060).

INTRODUCTION: The estimate of people with clinical Alzheimer's disease (AD) and mild cognitive impairment provides an understanding of the disease burden. METHODS: We estimated people with cognitive impairment using a quasibinomial regression model in 10,342 participants with cognitive test scores. RESULTS: The 2020 US Census-adjusted prevalence of clinical AD was 11.3% (95% confidence interval [CI] = 10.7-11.9): 10.0% among non-Hispanic Whites, 14.0% among Hispanics, and 18.6% among non-Hispanic Blacks. We estimate that in 2020, 6.07 (95% CI = 5.75-6.38) million people were living with clinical AD, which increases to 13.85 (95% CI = 12.98-14.74) million in 2060, 423% higher among Hispanics, 192% higher among Blacks, and 63% higher among Whites. However, there are predicted to be more significant increases in later years among those over 85 and women compared to men. DISCUSSION: The number of people with clinical AD will increase as the "baby boom" generation reaches older ages, exerting a strong upward influence on disease burden.

Evidence-Based Use of Levothyroxine/Liothyronine Combinations in Treating Hypothyroidism: A Consensus Document.

BACKGROUND: Fourteen clinical trials have not shown a consistent benefit of combination therapy with levothyroxine (LT4) and liothyronine (LT3). Despite the publication of these trials, combination therapy is widely used and patients reporting benefit continue to generate patient and physician interest in this area. Recent scientific developments may provide insight into this inconsistency and guide future studies. METHODS: The American Thyroid Association (ATA), British Thyroid Association (BTA), and European Thyroid Association (ETA) held a joint conference on November 3, 2019 (live-streamed between Chicago and London) to review new basic science and clinical evidence regarding combination therapy with presentations and input from 12 content experts. After the presentations, the material was synthesized and used to develop Summary Statements of the current state of knowledge. After review and revision of the material and Summary Statements, there was agreement that there was equipoise for a new clinical trial of combination therapy. Consensus Statements encapsulating the implications of the material discussed with respect to the design of future clinical trials of LT4/LT3 combination therapy were generated. Authors voted upon the Consensus Statements. Iterative changes were made in several rounds of voting and after comments from ATA/BTA/ETA members. RESULTS: Of 34 Consensus Statements available for voting, 28 received at least 75% agreement, with 13 receiving 100% agreement. Those with 100% agreement included studies being powered to study the effect of deiodinase and thyroid hormone transporter polymorphisms on study outcomes, inclusion of patients dissatisfied with their current therapy and requiring at least 1.2 µg/kg of LT4 daily, use of twice daily LT3 or preferably a slow-release preparation if available, use of patient-reported outcomes as a primary outcome (measured by a tool with both relevant content validity and responsiveness) and patient preference as a secondary outcome, and utilization of a randomized placebo-controlled adequately powered double-blinded parallel design. The remaining statements are presented as potential additional considerations. DISCUSSION: This article summarizes the areas discussed and presents Consensus Statements to guide development of future clinical trials of LT4/LT3 combination therapy. The results of such redesigned trials are expected to be of benefit to patients and of value to inform future thyroid hormone replacement clinical practice guidelines treatment recommendations.

Accelerating functional gene discovery in osteoarthritis.

Osteoarthritis causes debilitating pain and disability, resulting in a considerable socioeconomic burden, yet no drugs are available that prevent disease onset or progression. Here, we develop, validate and use rapid-throughput imaging techniques to identify abnormal joint phenotypes in randomly selected mutant mice generated by the International Knockout Mouse Consortium. We identify 14 genes with functional involvement in osteoarthritis pathogenesis, including the homeobox gene Pitx1, and functionally characterize 6 candidate human osteoarthritis genes in mouse models. We demonstrate sensitivity of the methods by identifying age-related degenerative joint damage in wild-type mice. Finally, we phenotype previously generated mutant mice with an osteoarthritis-associated polymorphism in the Dio2 gene by CRISPR/Cas9 genome editing and demonstrate a protective role in disease onset with public health implications. We hope this expanding resource of mutant mice will accelerate functional gene discovery in osteoarthritis and offer drug discovery opportunities for this common, incapacitating chronic disease.

Evidence-Based Use of Levothyroxine/Liothyronine Combinations in Treating Hypothyroidism: A Consensus Document.

Background: Fourteen clinical trials have not shown a consistent benefit of combination therapy with levothyroxine (LT4) and liothyronine (LT3). Despite the publication of these trials, combination therapy is widely used and patients reporting benefit continue to generate patient and physician interest in this area. Recent scientific developments may provide insight into this inconsistency and guide future studies. Methods: The American Thyroid Association (ATA), British Thyroid Association (BTA), and European Thyroid Association (ETA) held a joint conference on November 3, 2019 (live-streamed between Chicago and London) to review new basic science and clinical evidence regarding combination therapy with presentations and input from 12 content experts. After the presentations, the material was synthesized and used to develop Summary Statements of the current state of knowledge. After review and revision of the material and Summary Statements, there was agreement that there was equipoise for a new clinical trial of combination therapy. Consensus Statements encapsulating the implications of the material discussed with respect to the design of future clinical trials of LT4/LT3 combination therapy were generated. Authors voted upon the Consensus Statements. Iterative changes were made in several rounds of voting and after comments from ATA/BTA/ETA members. Results: Of 34 Consensus Statements available for voting, 28 received at least 75% agreement, with 13 receiving 100% agreement. Those with 100% agreement included studies being powered to study the effect of deiodinase and thyroid hormone transporter polymorphisms on study outcomes, inclusion of patients dissatisfied with their current therapy and requiring at least 1.2 µg/kg of LT4 daily, use of twice daily LT3 or preferably a slow-release preparation if available, use of patient-reported outcomes as a primary outcome (measured by a tool with both relevant content validity and responsiveness) and patient preference as a secondary outcome, and utilization of a randomized placebo-controlled adequately powered double-blinded parallel design. The remaining statements are presented as potential additional considerations. Discussion: This article summarizes the areas discussed and presents Consensus Statements to guide development of future clinical trials of LT4/LT3 combination therapy. The results of such redesigned trials are expected to be of benefit to patients and of value to inform future thyroid hormone replacement clinical practice guidelines treatment recommendations.

Temporal Pole Responds to Subtle Changes in Local Thyroid Hormone Signaling.

To study thyroid hormone (TH) signaling in the human brain, we analyzed published microarray data sets of the temporal pole (Brodmann area 38) of 19 deceased donors. An index of TH signaling built on the expression of 19 well known TH-responsive genes in mouse brains (T3S+) varied from 0.92 to 1.1. After Factor analysis, T3S+ correlated independently with the expression of TH transporters (MCT8, LAT2), TH receptor (TR) beta and TR coregulators (CARM1, MED1, KAT2B, SRC2, SRC3, NCOR2a). Unexpectedly, no correlation was found between T3S+ vs DIO2, DIO3, SRC1, or TRα. An unbiased systematic analysis of the entire transcriptome identified a set of 1649 genes (set #1) with strong positive correlation with T3S+ (r > 0.75). Factor analysis of set #1 identified 2 sets of genes that correlated independently with T3S+, sets #2 (329 genes) and #3 (191 genes). When processed through the Molecular Signatures Data Base (MSigDB), both sets #2 and #3 were enriched with Gene Ontology (GO)-sets related to synaptic transmission and metabolic processes. Ranking individual human brain donors according to their T3S+ led us to identify 1262 genes (set #4) with >1.3-fold higher expression in the top half. The analysis of the overlapped genes between sets #1 and #4 resulted in 769 genes (set #5), which have a very similar MSigDB signature as sets #2 and #3. In conclusion, gene expression in the human temporal pole can be assessed through T3S+ and fluctuates with subtle variations in local TH signaling.

Remote Blood Biomarkers of Longitudinal Cognitive Outcomes in a Population Study.

OBJECTIVE: The longitudinal association of the blood biomarkers total tau (t-tau), neurofilament light (Nf-L), and glial fibrillary acidic protein (GFAP) with common sporadic Alzheimer disease (AD) and cognitive decline is not established. METHODS: Using a single molecule array technology, ultrasensitive immunoassays for serum concentrations of t-tau, Nf-L, and GFAP were measured in a population sample of 1,327 participants (60% African Americans and women) who had a clinical evaluation for AD, had completed in-home cognitive assessments, and had undergone 1.5T structural magnetic resonance imaging. RESULTS: Higher concentrations of serum biomarkers were associated with the development of clinical AD; especially, the time-specific associations were notable: t-tau 8 to 16 years, and Nf-L and GFAP 4 to 8 years prior to clinical AD. Serum biomarkers were associated with faster cognitive decline over 16 years; baseline t-tau > 0.40pg/ml had 30% faster decline, Nf-L > 25.5pg/ml had 110% faster decline, and GFAP > 232pg/ml had 130% faster decline compared to those in the lowest quartile. Participants with baseline GFAP > 232pg/ml showed 160% faster decline in hippocampal volume compared to those with values < 160pg/ml. Additionally, higher baseline t-tau was associated with faster increase in 3rd ventricular volume, and baseline Nf-L and GFAP were associated with faster decline in cortical thickness. INTERPRETATION: Serum t-tau, Nf-L, and GFAP predict the development of sporadic AD and cognitive decline, and changes in structural brain characteristics, suggesting their usefulness not only as screening and predictive biomarkers, but also in capturing the pathogenesis of Alzheimer dementia. ANN NEUROL 2020;88:1065-1076.

Temporal changes in the likelihood of dementia and MCI over 18 years in a population sample.

OBJECTIVE: To examine the temporal changes in the likelihood of dementia and mild cognitive impairment (MCI) between 1993 and 2012 using a short battery of cognitive tests. METHODS: A cohort of 10,342 participants underwent a short battery of cognitive tests collected during triennial in-home interviews with 2,794 of those evaluated for the clinical diagnosis of dementia and MCI. We used a generalized logit regression model to estimate the likelihood of dementia and MCI, and a quasibinomial regression model to examine the temporal changes in those likelihood scores. RESULTS: A short battery of cognitive tests-delayed story recall test, Symbol Digit Modalities Test, and the Mini-Mental State Examination-were associated with the clinical diagnosis of dementia and MCI. The classification accuracy of likelihood scores was 0.92 for dementia and 0.85 for MCI. After adjusting for age, race/ethnicity, and education, the likelihood of dementia in the population decreased from 21.6% (95% confidence interval [CI] 20.9%-22.3%) to 18.9% (95% CI 18.1%-19.7%) between 1993-1996 and 2000-2002 and showed no significant decline between 2000-2002 and 2009-2012 (-0.2%, 95% CI -1.1% to 0.7%). The estimated likelihood of MCI remained similar between 1993-1996 and 2009-2012 (29.0%, 95% CI 27.9%-30.1%), but showed a nonsignificant decrease in 2000-2002. CONCLUSION: The likelihood scores based on a short battery of cognitive tests can serve as a measure of dementia and MCI in epidemiologic studies. The decline in the likelihood of dementia and MCI over earlier years was not sustained in later years.

Race, APOEɛ4, and Long-Term Cognitive Trajectories in a Biracial Population Sample.

BACKGROUND: The association of the APOEɛ4 allele with incident Alzheimer's dementia is higher among European Americans (EAs) than African Americans (AAs), but similar for the rate of cognitive decline. OBJECTIVE: To examine the racial differences in the association of the APOEɛ4 allele with incident Alzheimer's dementia and cognitive decline. METHODS: Using a population-based sample of 5,117 older adults (66% AAs and 63% females), we identified cognitive trajectory groups from a latent class mixed model and examined the association of the APOEɛ4 allele with these groups. RESULTS: The frequency of the APOEɛ4 allele was higher among AAs than EAs (37% versus 26%). Four cognitive trajectories were identified: slow, mild, moderate, and rapid. Overall, AAs had a lower baseline global cognition than EAs, and a higher proportion had rapid (7% versus 5%) and moderate (20% versus 15%) decline, but similar mild (44% versus 46%), and lesser slow (29% versus 34%) decline compared to EAs. Additionally, 25% of AAs (13% of EAs) with mild and 5% (<1% of EAs) with slow decline were diagnosed with incident Alzheimer's dementia. The APOEɛ4 allele was associated with higher odds of rapid and moderate decline compared to slow decline among AAs and EAs, but not with mild decline. CONCLUSIONS: AAs had lower cognitive levels and were more likely to meet the cognitive threshold for Alzheimer's dementia among mild and slow decliners, explaining the attenuated association of the ɛ4 allele with incident Alzheimer's dementia among AAs.

The Swinging Pendulum in Treatment for Hypothyroidism: From (and Toward?) Combination Therapy.

Thyroid hormone replacement for hypothyroidism can be achieved via several approaches utilizing different preparations of thyroid hormones, T3, and/or T4. "Combination therapy" involves administration of both T3 and T4, and was technically the first treatment for hypothyroidism. It was lauded as a cure for the morbidity and mortality associated with myxedema, the most severe presentation of overt hypothyroidism. In the late nineteenth and the early Twentieth centuries, combination therapy per se could consist of thyroid gland transplant, or more commonly, consumption of desiccated animal thyroid, thyroid extract, or thyroglobulin. Combination therapy remained the mainstay of therapy for decades despite development of synthetic formulations of T4 and T3, because it was efficacious and cost effective. However, concerns emerged about the consistency and potency of desiccated thyroid hormone after cases were reported detailing either continued hypothyroidism or iatrogenic thyrotoxicosis. Development of the TSH radioimmunoassay and discovery of conversion of T4-to-T3 in humans led to a major transition in clinical practices away from combination therapy, to adoption of levothyroxine "monotherapy" as the standard of care. Levothyroxine monotherapy has a favorable safety profile and can effectively normalize the serum TSH, the most sensitive marker of hypothyroidism. Whether levothyroxine monotherapy restores thyroid hormone signaling within all tissues remains controversial. Evidence of persistent signs and symptoms of hypothyroidism during levothyroxine monotherapy at doses that normalize serum TSH is mounting. Hence, in the last decade there has been acknowledgment by all thyroid professional societies that there may be a role for the use of combination therapy; this represents a significant shift in the clinical practice guidelines. Further bolstering this trend are the recent findings that the Thr92AlaD2 polymorphism may reduce thyroid hormone signaling, resulting in localized and systemic hypothyroidism. This strengthens the hypothesis that treatment options could be personalized, taking into consideration genotypes and comorbidities. The development of long-acting formulations of liothyronine and continued advancements in development of thyroid regenerative therapy, may propel the field closer to adoption of a physiologic thyroid hormone replacement regimen with combination therapy.

Type 2 deiodinase polymorphism causes ER stress and hypothyroidism in the brain.

Levothyroxine (LT4) is a form of thyroid hormone used to treat hypothyroidism. In the brain, T4 is converted to the active form T3 by type 2 deiodinase (D2). Thus, it is intriguing that carriers of the Thr92Ala polymorphism in the D2 gene (DIO2) exhibit clinical improvement when liothyronine (LT3) is added to LT4 therapy. Here, we report that D2 is a cargo protein in ER Golgi intermediary compartment (ERGIC) vesicles, recycling between ER and Golgi. The Thr92-to-Ala substitution (Ala92-D2) caused ER stress and activated the unfolded protein response (UPR). Ala92-D2 accumulated in the trans-Golgi and generated less T3, which was restored by eliminating ER stress with the chemical chaperone 4-phenyl butyric acid (4-PBA). An Ala92-Dio2 polymorphism-carrying mouse exhibited UPR and hypothyroidism in distinct brain areas. The mouse refrained from physical activity, slept more, and required additional time to memorize objects. Enhancing T3 signaling in the brain with LT3 improved cognition, whereas restoring proteostasis with 4-PBA eliminated the Ala92-Dio2 phenotype. In contrast, primary hypothyroidism intensified the Ala92-Dio2 phenotype, with only partial response to LT4 therapy. Disruption of cellular proteostasis and reduced Ala92-D2 activity may explain the failure of LT4 therapy in carriers of Thr92Ala-DIO2.

Amiodarone and thyroid physiology, pathophysiology, diagnosis and management.

Although amiodarone is considered the most effective antiarrhythmic agent, its use is limited by a wide variety of potential toxicities. The purpose of this review is to provide a comprehensive "bench to bedside" overview of the ways amiodarone influences thyroid function. We performed a systematic search of MEDLINE to identify peer-reviewed clinical trials, randomized controlled trials, meta-analyses, and other clinically relevant studies. The search was limited to English-language reports published between 1950 and 2017. Amiodarone was searched using the terms adverse effects, hypothyroidism, myxedema, hyperthyroidism, thyroid storm, atrial fibrillation, ventricular arrhythmia, and electrical storm. Google and Google scholar as well as bibliographies of identified articles were reviewed for additional references. We included 163 germane references in this review. Because amiodarone is one of the most frequently prescribed antiarrhythmic drugs in the United States, the mechanistic, diagnostic and therapeutic information provided is relevant for practicing clinicians in a wide range of medical specialties.