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

Pycnogenol® improves cognitive function in post-stroke patients: a 6 month-study

BACKGROUND

This pilot study in post-stroke patients evaluated the effects of supplementation with Pycnogenol® on alterations in cognitive functions (COFU) over a period of 6 months, starting 4 weeks after the stroke.

METHODS

The effects of supplementation - possibly acting on residual brain edema, on global cognitive function, attention and on mental performance - were studied. A control group used standard management (SM) and the other group added Pycnogenol®, 150 mg daily to SM.

RESULTS

38 post-stroke patients completed the 6-month-study, 20 in the Pycnogenol® group and 18 in the control group. No side effects were observed with the supplement. The tolerability was very good. The patients included into the two groups were comparable for age, sex and clinical distribution. There were 2 dropouts in the control group, due to non-medical problems. Main COFU parameters (assessed by a cognitive questionnaire) were significantly improved (all single items) with the supplement compared to controls (P<0.05). Additional observations indicate that Pycnogenol® patients experienced significantly less mini-accidents (including falls) than controls (P<0.05). The incidences of (minor) psychotic episodes or conflicts and distress and other problems including rare occurrence of minor hallucinations, were lower with the supplementation than in controls (P<0.05). Single observations concerning daily tasks indicated a better effect of Pycnogenol® compared to controls (P<0.05). Plasma free radicals also decreased significantly with the supplement in comparison to controls (P<0.05). Globally, supplemented subjects had a better recovery than controls.

CONCLUSIONS

In post-stroke subjects, Pycnogenol® supplementation resulted in better recovery outcome and faster COFU 'normalization' after the stroke in comparison with SM; it can be considered a safe, manageable post-stroke, adjuvant management possibly reducing local brain edema. Nevertheless, more patients and a longer period of evaluation are needed to confirm these results.

Attention Deficit Hyperactivity Disorder Misdiagnosis: Why Medical Evaluation Should Be a Part of ADHD Assessment

INTRODUCTION

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder that interferes with multiple aspects of daily functioning and is associated with impairments in several domains. It may affect academic, educational, vocational, social, emotional, interpersonal, and health domains, and worsen risks to health outcomes.

OBJECTIVE

To identify and discuss medical conditions that commonly present with symptoms resembling ADHD.

METHOD

This review is selective and not systematic. It is conducted through a focused literature search through PubMed, Google Scholar, and EMBASE. Search term included "ADHD misdiagnosis", "medical conditions with ADHD like symptoms", "ADHD AND medical problems".

EXCLUSION

giftedness, high IQ, and any article that does not list medical conditions. The limits applied were the following: the work must have been published in the past 20 years, be on humans, and be in the English language.

RESULTS

There are several medical conditions that can be misdiagnosed as ADHD and may show a similar presentation to ADHD, particularly with inattentive symptoms. Examples include, but are not limited to, absence seizure disorder, diabetes, thyroid dysfunction, sleep deprivation, post-concussion states, inflammatory bowel disease, iron deficiency states and anemia, and disordered breathing.

CONCLUSIONS

Our review suggests that a thorough medical evaluation should be conducted prior to the diagnosis of ADHD. Allied health professionals and psychologists who diagnose ADHD should seek medical clearance from a physician prior to making the ADHD diagnosis in order to reduce misdiagnosis rates and improve patient outcomes. ADHD diagnosis should follow guidelines and be carried out under a systematic standardized approach. A full medical evaluation should be conducted to assess for medical conditions that may look like ADHD or be associated with ADHD.

Association Between Thyroid-Stimulating Hormone Level and Bell's Palsy

OBJECTIVE

To investigate whether dysregulated thyroid hormone function is associated with Bell's palsy.

STUDY DESIGN

Cross-sectional.

SETTING

Electronic medical record database of Clalit Health Services (CHS). CHS is an Israeli payer-provider, integrated health care system, serving >4.5 million members (54% of the Israeli population).

PATIENTS

Older than 18 years with Bell's palsy, during 2002 to 2019.

INTERVENTIONS

None.

METHODS

A total of 1,374 patients with Bell's palsy who had thyroid-stimulating hormone (TSH) blood levels measured up to 60 days before the palsy were matched (1:2) for age and sex with 2,748 controls who had TSH blood levels and no history of Bell's palsy.

RESULTS

Retrospective review of the CHS database, from 2002 to 2019 yielded 11,268 patients with Bell's palsy, of which, 1,374 met the inclusion criteria. Mean age was 57.9 years, and 61.4% were female. A higher percentage of patients in the Bell's palsy group had low TSH (≤0.55 mIU/L) compared with controls (5.7% vs. 3.6%, p < 0.001). Low TSH compared with TSH > 0.55 mIU/L, was independently associated with 1.45-fold increased odds for having Bell's palsy (95% CI 1.11-2.02, p < 0.001), when controlled for age, sex, body mass index, diabetes, hypertension, prior cerebrovascular accident, hemoglobin level, and purchasing thyroid hormone drugs. Among the patients with TSH ≤ 0.55 mIU/L, 95.5% had normal free thyroxin and 97.7% had normal free triiodothyronine levels (subclinical hyperthyroidism). For 47.1% of patients, TSH remained ≤0.55 mIU/L, 3 to 12 months after the Bell's palsy occurred and most patients had normal free thyroxin (95.4%) and normal free triiodothyronine (91.8%).

CONCLUSIONS

Subclinical hyperthyroidism is independently associated with Bell's palsy after controlling for multiple confounding factors.

Hyperthyroidism leads learning and memory impairment possibly via GRIN2B expression alterations

The hippocampus as an important structure for learning and memory functions contains a high level of thyroid hormone receptors. Although there are numerous studies investigating the effects of thyroid hormones on cognitive dysfunction and psychiatric symptoms, the underlying molecular processes of these disorders have not yet been fully elucidated. In the present study, 24 male adult rats (4 months) were divided into 3 groups: control group, sham group and hyperthyroid group. Hyperthyroid group and sham group were treated with l-thyroxine or saline for 21 days. Each group was exposed to Morris water maze testing (MWMT), measuring their performance in a hidden-platform spatial task. After learning and memory tests, intracardiac blood was taken from the rats for serum thyroxine levels. Following blood collection, the rats were decapitated to isolate hippocampal tissue. GRIN2A, GRIN2B, BDNF, cFOS, Cdk5, cdk5r1 (p35), and cdk5r2 (p39) gene expression were evaluated using quantitative reverse transcriptase-PCR. Serum thyroxine level was found to be higher in hyperthyroid rats than in the control and sham groups. According to our MWMT findings, the memory performance of the hyperthyroid group was significantly impaired compared to the control and sham groups (p < 0.05). In the hippocampus, the GRIN2A gene expression level was decreased in the sham group, and the GRIN2B gene expression level was decreased in the sham and hyperthyroid groups compared to the control group (p < 0.05). There was no significant difference in other genes (p > 0.05). Hyperthyroidism impaired hippocampus-dependent spatial memory. Hyperthyroidism caused decreased level of GRIN2B gene expression in the hippocampus.

Resting Electroencephalography Differences Between Eyes-Closed and Eyes-Open Conditions in Children with Subclinical Hypothyroidism

OBJECTIVE

Electroencephalography changes that occur during the transition from eyes-closed to the eyes-open state in resting condition are related to the early phase of sensory processing and are defined as activation. The present study aimed to reveal the potential deteriorations that may occur in the initial period of sensory processing in resting electroencephalography between children with subclinical hypothyroidism and a control group.

MATERIALS AND METHODS

Electroencephalographies of 15 children with subclinical hypothyroidism and 15 healthy children aged 10 to 17 years were recorded for 2 minutes for EC and 2 minutes for eyes-open conditions in resting state. Absolute electroencephalography band powers (μV2 ) within the delta, theta, alpha, and beta frequency bands were calculated in Fz, Cz, Pz, and Oz electrodes, respectively, for eyes-closed and eyes-open conditions.

RESULTS

The results show that, although there was no noteworthy difference between the powers of the electroencephalography frequency bands of children with subclinical hypothyroidism and healthy children during the eyes-open condition, the alpha powers of the control group were significantly higher in all electrodes during the eyes-closed condition. Furthermore, the powers of all frequency bands were observed to decrease in the eyes-open condition in the control group. However, the same net decrease was not observed in the frequency powers of children with subclinical hypothyroidism.

CONCLUSION

According to the results of this study, children with subclinical hypothyroidism may experience information processing impairments starting in the early stages of sensory processing.

Cognitive impairment in women newly diagnosed with thyroid cancer before treatment

PURPOSE

The study aims to assess cognitive function in women newly diagnosed with non-metastatic thyroid cancer before any treatment and to identify factors associated with cognitive problems.

METHODS

Korean women newly diagnosed with thyroid cancer awaiting initial surgical treatment (n = 130) completed neuropsychological tests and self-report questionnaires on symptom distress and psychological distress. Additionally, information on thyroid function was obtained through a medical chart audit. Descriptive statistics and multivariable regression analyses were performed to describe the incidence of cognitive problems and to identify possible predictors of neuropsychological performance.

RESULTS

Approximately 95% of women newly diagnosed with thyroid cancer had impaired neuropsychological test scores on one or more tests of attention and cognitive control. Further analyses found that 78% of women met both the Global Deficit Score and the International Cancer and Cognition Task Force criteria for impairment. Finally, regression analyses found that older age, fewer years of education, greater depressed mood, and having a hypothyroid state but not having a comorbid condition, fatigue, sleep problems, symptom burden, or symptom interference were associated with worse neuropsychological test performance in this sample. Additional explorative regression analysis using mean T-scores corrected for age, education, and gender continued to find that hypothyroid state was associated with worse neuropsychological test performance.

CONCLUSIONS

Findings suggest that individuals newly diagnosed with non-metastatic thyroid cancer are vulnerable to cognitive deficits at diagnosis before any treatment. As such, healthcare workers should assess individuals newly diagnosed with thyroid cancer diagnosis awaiting treatment for the disease for cognitive deficits and intervene to reduce symptom distress and optimize function.

Update on subclinical thyroid dysfunction

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

Genetic, clinical, and biochemical aspects of patients with Alzheimer disease

Background

The most common form of dementia is Alzheimer’s disease (AD). The clinical manifestations of AD are loss of memory that is progressive and deterioration in cognitive function. The objective of this study is to find patterns of AD among patients regarding clinical aspects, psychological aspects, and laboratory aspects, as well as to determine the role of some genes (APOE1, APOE2, and TMEM106B) in the pathogenesis of AD. In this case–control study, 40 patients with AD were recruited from the inpatient neurology departments and outpatient neurology clinics of the university hospitals in the period of January 1 to December 31, 2017. Furthermore, 40 cross-matched control patients underwent a complete history taking, neurological examination, brain MRI or CT, psychometric tests, thyroid function, and lipid profile measurements. Extracted DNA was quantified using a nanodrop analyzer (ND-1OOO) spectrophotometer for TMEM106B (rs1990622), APOE2 (rs429358), and APOE1 (rs7412).

Results

All subtypes of lipid profiles were significantly higher in patients with AD than the controls. There was a significant difference between the two groups regarding TMEM106B. There was an insignificant difference regarding thyroid hormones T3, T4, and TSH between patients and controls. There was no significant difference between AD patients and the control group regarding APOE-1 and APOE-2. Patients were worse than controls in tests of cognition, such as The Cognitive Abilities Screening Instrument (CASI) and auditory number and letter span test. In addition, AD patients had more depression than controls.

Conclusion

There may be a significant role of a high lipid profile and TMEM106B expression in the pathogenesis of AD.

Pathophysiology and Clinical Features of Neuropsychiatric Manifestations of Thyroid Disease

Thyroid hormones (TH) have a cardinal role in the development of the central nervous system during embryogenesis and early infancy. However, the TH-responsive genes in the developing brain cease to respond to TH in adulthood. Nevertheless, thyroid dysfunction in adults is commonly associated with a host of cognitive and psychiatric problems. Cognitive decline, dysphoria, and depression are common manifestations of overt hypothyroidism while hyperthyroidism can cause agitation, acute psychosis, and apathy, especially in older people. Whereas levothyroxine treatment can reverse dementia in the setting of hypothyroidism, the effect of levothyroxine on depressive symptoms in subjects with subclinical hypothyroidism is controversial. The use of supraphysiologic doses of TH to treat depression refractory to antidepressant remains a viable therapeutic tool with the caveat that excessive doses of thyroid hormone to treat depression may have potentially damaging effects on other organ systems. The present communication describes the pathophysiology of neuropsychiatric manifestations of thyroid disease, including changes in neurotransmission, alterations in neuronal or glial cell gene expression, blood-brain barrier dysfunction, increased risk of cerebrovascular disease, and occasionally cerebral inflammatory disease in the context of autoimmune thyroid disease. Elucidating the molecular mechanisms of TH effect on cerebral tissue will help identify novel therapeutic targets for managing people with neuropsychiatric disorders.

Genetically Determined TSH Level Within Reference Range Is Inversely Associated With Alzheimer Disease

CONTEXT

Contradictory findings were reported in observational studies on the association of thyroid function (thyrotropin [TSH] and free thyroxine [FT4] levels) with Alzheimer disease (AD).

OBJECTIVE

This work aims to determine whether genetically determined TSH/FT4 levels within reference range are causally associated with AD.

METHODS

A bidirectional, 2-sample mendelian randomization (MR) study was conducted. With summary statistics from the largest genome-wide association studies (GWAS)/GWAS meta-analysis of TSH level(n ≥ 54 288), FT4 level(n = 49 269), and AD (71 880 cases; 383 378 controls), we used an MR approach to evaluate the bidirectional causal relationship between TSH/FT4 levels and AD. The inverse-variance weighted method was adopted as the main analysis.

RESULTS

One SD increase in genetically determined TSH level within reference range was causally associated with a reduced risk of AD (odds ratio: 0.988; 95% CI, 0.977-0.998). A similar inverse association was observed in sex-specific analysis. The causal association was attenuated after adjustment for atrial fibrillation and blood pressure, suggesting they may mediate the causal pathway. A positive causal effect of AD on TSH level was detected only in male participants. This male-specific feedback loop may explain why the largest cohort study to date (Rotterdam Study) demonstrated a null observational association in men. Null association was observed between FT4 level and AD in both directions.

CONCLUSION

Genetic predisposition to increased TSH level, even within reference range, may lower the risk of AD, with atrial fibrillation, systolic, and diastolic blood pressure as possible mediators. Given the higher magnitude of risk reduction observed in the Rotterdam Study, whether the causal estimates derived from this MR study are underestimated warrants further investigation.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Changes in Serum Thyroid Function Predict Cognitive Decline in the Very Old: Longitudinal Findings from the Newcastle 85+ Study

Background: Low serum thyrotropin (TSH) has been associated with an increased risk of cognitive impairment in observational studies of older individuals, but the mechanism underlying this is unclear. We investigated the association between changes in thyroid status and cognitive impairment in very old adults, using prospective data from the Newcastle 85+ study. Method: A cohort of 85-year-old individuals was assessed for health status and thyroid function. Complete data from a comprehensive multidimensional measure of health and repeat thyroid function were available for 642 participants with normal free thyroid hormones and TSH levels ranging between 0.1 and 10 mU/L. Cognitive performance, assessed using Mini-Mental State Examination (MMSE) and Cognitive Drug Research battery was examined by using linear mixed, logistic regression, and Cox proportional hazard models in relation to baseline and 3-year changes in serum TSH, free thyroxine (fT4), and free triiodothyronine (fT3). Results: Over 3 years, declining serum TSH was associated with reductions in fT4 and fT3, and an increased risk of incident cognitive impairment by 5 years (odds ratio1.77 [95% confidence interval: 1.19-2.61]; p = 0.004). A greater reduction in MMSE score was associated with larger TSH decline, at 3 (p = 0.001) and 5 years (p < 0.001), respectively. Steady fT4 concentrations were found in participants with rising TSH. Conclusions: In contrast to physiological expectation, in this group of 85-year-olds, a declining serum TSH was associated with reductions in free thyroid hormones over time. A decreasing serum TSH trajectory over time anticipated cognitive decline in later life. Declining TSH concentrations are a biomarker for cognitive impairment in later life.

Endocrine dysfunction and cognitive impairment

Dementia is a highly prevalent chronic disease among the older population, affecting more than 50 million people worldwide and representing a huge healthcare, social and economic burden. Dementia, and in particular Alzheimer's disease, prevalence is expected to raise within the next few years. Unfortunately, no disease-modifying therapies are available so far, despite a plethora of clinical trials targeting the hallmarks of Alzheimer's disease. Given these premises, it appears crucial to address not only the neuropathological correlates of the disease, but also the modifiable risk factors. Among them, evidence suggest a role of the endocrine system not only in the brain development, but also in the maintenance of its health, having neurotrophic, antioxidant and metabolic functions crucial for the cognitive abilities. This review focuses on the evidence evaluating the impact of the endocrine systems, in particular thyroid function, insulin resistance, parathyroid hormone, vitamin D and sexual hormones on cognitive status. Results from epidemiological, preclinical and some clinical studies demonstrated the link between thyroid, parathyroid hormone and vitamin D and cognitive status, between diabetes, and insulin resistance in particular, and dementia, between sexual and adrenal hormones, particularly estrogen variation at menopause, and cognitive decline. The growing interest on the modifiable risks factors of cognitive decline increased the knowledge about the complex interplay of endocrine systems and cognition, highlighting the need and the usefulness of a multidisciplinary approach to the prevention of a complex and devastating disease.

Royal Jelly as an Intelligent Anti-Aging Agent-A Focus on Cognitive Aging and Alzheimer's Disease: A Review

The astronomical increase of the world's aged population is associated with the increased prevalence of neurodegenerative diseases, heightened disability, and extremely high costs of care. Alzheimer's Disease (AD) is a widespread, age-related, multifactorial neurodegenerative disease that has enormous social and financial drawbacks worldwide. The unsatisfactory outcomes of available AD pharmacotherapy necessitate the search for alternative natural resources that can target various the underlying mechanisms of AD pathology and reduce disease occurrence and/or progression. Royal jelly (RJ) is the main food of bee queens; it contributes to their fertility, long lifespan, and memory performance. It represents a potent nutraceutical with various pharmacological properties, and has been used in a number of preclinical studies to target AD and age-related cognitive deterioration. To understand the mechanisms through which RJ affects cognitive performance both in natural aging and AD, we reviewed the literature, elaborating on the metabolic, molecular, and cellular mechanisms that mediate its anti-AD effects. Preclinical findings revealed that RJ acts as a multidomain cognitive enhancer that can restore cognitive performance in aged and AD models. It promotes brain cell survival and function by targeting multiple adversities in the neuronal microenvironment such as inflammation, oxidative stress, mitochondrial alterations, impaired proteostasis, amyloid-β toxicity, Ca excitotoxicity, and bioenergetic challenges. Human trials using RJ in AD are limited in quantity and quality. Here, the limitations of RJ-based treatment strategies are discussed, and directions for future studies examining the effect of RJ in cognitively impaired subjects are noted.

Is Hyperthyroidism a Possible Etiology of Early Onset Dementia?

Dementia, a disabling syndrome of the elderly characterized by the decline in memory and cognition, is increasing in incidence and affects not only the individual but also their family and close ones. Hyperthyroidism can mimic many other diseases and untreated hyperthyroidism can lead to adverse problems of various systems including the heart, bones, muscles, menstrual cycle, and fertility. In this article, we have tried to evaluate the association between hyperthyroidism and dementia, as well as the impact of hyperthyroidism management in the treatment and prevention of dementia. Studies available in the PubMed database have been used, excluding animal studies and including studies of adults above the age of 50. The analysis of studies reveals that thyroid dysfunction can lead to cognitive impairment. It has not been able to prove that hyperthyroidism can lead to an earlier onset of dementia. But subclinical hyperthyroidism, thyroid-stimulating hormone (TSH) levels below the normal range, and high free thyroxine (T4) levels increase the risk of dementia among the elderly. The possible mechanisms involved in this association have also been discussed. Thus, we concluded that it is essential to detect and manage hyperthyroidism at an earlier stage since hyperthyroidism increases the risk of dementia. The possibility of using antithyroid treatment in euthyroid dementia is yet to be studied extensively.

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.

The effects of thyroid hormones on memory impairment and Alzheimer's disease

Thyroid hormones (THs) have a wide and important range of effects within the central nervous system beginning from fetal life and continuing throughout the adult life. Thyroid disorders are one of the major causes of cognitive impairment including Alzheimer's disease (AD). Several studies in recent years have indicated an association between hypothyroidism or hyperthyroidism and AD. Despite available evidence for this association, it remains unclear whether thyroid dysfunction results from or contributes to the progression of AD. This review discusses the role of THs in learning and memory and summarizes the studies that have linked thyroid function and AD. Eventually, we elaborate how THs may be effective in treating AD by putting forward potential mechanisms.

Graves' disease, multinodular goiter and subclinical hyperthyroidism

Subclinical hyperthyroidism is a common clinical entity, defined by serum TSH below the reference range, with normal FT4 and FT3 levels in an asymptomatic patient. Whether or not subclinical hyperthyroidism should be treated remains a matter of debate. Cross-sectional and longitudinal population-based studies demonstrate association of subclinical hyperthyroidism with risk of atrial fibrillation and osteoporosis, and with cardiovascular and all-cause mortality. However, there are no randomized clinical trials addressing whether long-term health outcomes are improved by treating subclinical hyperthyroidism; in the absence of evidence one way or the other, it seems appropriate to use decision trees taking account of TSH concentration and presence of risk factors (age>65 years or post-menopause, osteoporosis and cardiac disease).

Auditory event-related potentials demonstrate early cognitive impairment in children with subclinical hypothyroidism

Background The aim of this study was to examine the cognitive functions of children with subclinical hypothyroidism (SH) and healthy children with the use of auditory event-related potentials (AERPs) and neuropsychological tests. Methods Twenty children aged between 8 and 17 years, diagnosed with SH, and 20 age-matched healthy controls were included in this study. A classical auditory oddball paradigm was applied during the electroencephalography (EEG) recordings, and event-related potentials (ERPs) were evaluated between the 0.5- and 20-Hz frequency intervals. P1, N1, P2, N2 and P3 amplitudes and latencies were measured in Fz, FCz, Cz, CPz, Pz and Oz electrodes. Additionally, a number of neuropsychological tests evaluating the reaction time and various cognitive functions were carried out. Results In children with SH, P3 amplitudes in FCz, Cz and CPz electrodes were significantly lower than those in controls (p < 0.05). In addition to this, the P1N1 and N1P2 peak-to-peak amplitude values were also found to be smaller for children with SH than controls (p < 0.05). With regard to the neuropsychological tests, no significant difference was observed between the SH and control groups on any of the cognitive test parameters, reaction time or correct response rates. Conclusions In the present study, while children with SH did not differ from controls with respect to their cognitive functions evaluated via neuropsychological tests, cognitive differences were detected via electrophysiological investigations. This result implies that implicit changes in cognition which are not yet overtly reflected on neuropsychological tests may be detected at an early stage in children with SH.

The relationship between thyroid function and cerebral blood flow in mild cognitive impairment and Alzheimer's disease

The thyroid hormones have been reported to be associated with cognitive decline and Alzheimer’s disease. The relationship between thyroid function within the normal range and cerebral blood flow in Alzheimer’s disease patients has been shown in a recent study. Mild cognitive impairment is often the first stage of Alzheimer’s disease; thus, early diagnosis is important. The present study investigated the relationship between thyroid function and regional cerebral blood flow in patients with mild cognitive impairment and Alzheimer’s disease. A total of 122 memory clinic outpatients who underwent thyroid function testing and single photon emission computed tomography were divided into mild cognitive impairment, Alzheimer’s disease, and Normal groups. Regional cerebral blood flow was calculated using a three-dimensional stereotactic region of interest template in an automated cerebral perfusion single photon emission computed tomography analysis system. Multiple regression analysis adjusted for age and sex was conducted to examine the relationships between thyroid hormones and regional cerebral blood flow. Thyroid stimulating hormone was significantly associated with regional cerebral blood flow in the bilateral temporal, bilateral pericallosal, and bilateral hippocampal regions in the mild cognitive impairment group. In the Alzheimer’s disease group, free triiodothyronine was significantly associated with regional cerebral blood flow in the bilateral parietal, right temporal, and bilateral pericallosal regions. The present study showed the association of thyroid stimulating hormone with regional cerebral blood flow in the mild cognitive impairment group and the association of free triiodothyronine with regional cerebral blood flow in the Alzheimer’s disease group. These study findings could contribute to the early diagnosis of mild cognitive impairment at general memory clinics and the prevention of subsequent progression to Alzheimer’s disease.

The relationship between quality of life, cognition, and thyroid status in Graves' disease

PURPOSE

To assess quality of life (QoL) and cognitive function among Graves' disease (GD) patients with different thyroid status, with and without ophthalmopathy.

METHODS

This is a cross-sectional clinic-based study involving 154 patients with GD (81.27% were female, mean age 45.6 ± SD 11.2 years) and 54 (35.06%) had ophthalmopathy. Data were collected after an informed consent from all patients was obtained. All patients completed the 36-Item Short Form Health Survey and Mini-Mental State Examination. Patients with ophthalmopathy also completed the Graves' Orbitopathy Quality of Life Questionnaire.

RESULTS

Patients with hyperthyroidism presented a greater impairment in QoL when compared to euthyroidism group. A lower score in physical role functioning was found in both subgroups with active disease (hyperthyroidism and euthyroidism using thionamides). A lower score was also seen in visual function, only in patients with hyperthyroidism, without difference in appearance. No difference was found in cognition between patients. Younger ages at diagnosis, male sex, euthyroidism and absence of ophthalmopathy were factors associated with better QoL, as well as a shorter disease duration was associated with better recall, attention and calculation.

CONCLUSIONS

An impairment in QoL among patients with active GD was evidenced, even in those receiving thionamides and in euthyroidism. Ophthalmopathy was a factor associated with a poor QoL and no clear evidence of cognitive impairment was demonstrated.

Thyroid disease in the perimenopause and postmenopause period

The interpretation of thyroid function tests should be cautiously made during the perimenopause and postmenopause period bearing in mind that physiologic changes do exist in this group of women in terms of secretion and metabolism of thyrotropin and thyroid hormones. Moreover the incidence of thyroid disorders increases in postmenopausal and elderly women. There is no consensus for screening postmenopausal women even though there is well-known evidence about the effect of thyroid status on cognitive function, cardiovascular risk, bone turnover, and longevity. The diagnosis of any thyroid disorder is challenging in these patients because the symptoms are more subtle and attributed to menopausal symptoms. Management requires more attention in this population than that of younger groups, because high doses of L-thyroxine can lead to cardiac complications and increased bone turnover. Furthermore radio-iodine is preferred in treatment of hyperthyroidism in older patients. The risk of nodular thyroid disease and thyroid cancers increases in this group. Although the diagnostic approach is the same as for young patients, the risk of surgery is high and disease prognosis is worse. Women with any form of thyroid disease should be treated according to the current guidelines. Decision for menopausal hormonal therapy should be individualized regardless of the concomitant presence of thyroid disorders.

Lack of Relationships Between Serum Prolactin Concentrations and Classical Cardiovascular Risk Factors in Eastern Croatian Older Adults

Background

Relationships between serum prolactin concentrations and various CV risk factors in older adults have rarely been assessed. The aim of this study was to examine the relationships between serum prolactin concentrations and CV risk factors in older patients with multiple CV risk factors.

Material/Methods

This case-control study included 92 patients, 50–89 years old (median, 69 years), with multiple CV risk factors. We used data from general practice electronic health records and biochemical laboratory tests. Patients were divided according to categories of CV risk factors.

Results

Serum prolactin concentrations were significantly higher in elderly people (≤65 vs. >65) and in men (70.65±58.02 vs. 150.82±114.05 mIU/L), as well as in patients with lower renal function (156.70±127.23 vs. 72.53±37.25 mIU/L, the bottom vs. top quartile of creatinine clearance), higher serum homocysteine and TSH concentrations, and in those who used NSAID and statins. Parameters indicating chronic inflammation (CRP) and renal function decline (creatinine clearance) were significantly and independently correlated with increased serum prolactin concentrations in multiple regression analysis.

Conclusions

When assessing the relationships between prolactin and CV risk factors in older people with multiple CV risk factors, the effect of renal function decline and chronic inflammation should receive attention.

Chronic Health Illnesses as Predictors of Mild Cognitive Impairment Among African American Older Adults

Approximately 5.5 million individuals are diagnosed with Alzheimer's disease (AD) dementia, a number which includes those with mild cognitive impairment and asymptomatic individuals with biomarkers of AD. There is a higher incidence of mild cognitive impairment (MCI) in African American populations as compared to White populations, even when controlling for sociodemographic factors. The existing body of ethnically/racially targeted research on MCI has been limited by few studies with the ability to generalize to African American communities. This study sought to examine whether medical conditions which occur at a higher rate in African American individuals increase the hazard of subsequent MCI development. A secondary data analysis of the National Alzheimer's Coordinating Center Uniform Data Set was employed to examine the associations between health conditions (congestive heart failure, traumatic brain injury, diabetes, hypertension, hypercholesterolemia, B12 deficiency, thyroid disease) and their relationship to MCI. The analytic sample included 2847 participants with 9872 observations. Binary logistic generalized estimating equation modeling was used to examine repeated measures over the course of 1-11 observations. Education was associated with MCI development, specifically those with some college or college graduates (p < 0.001) and more than college (p = 0.002). Female sex was associated with development of MCI (p < 0.001). African Americans with traumatic brain injury (TBI) were more likely to develop MCI (p < 0.001) compared to those with no reports of a TBI. Inactive thyroid conditions decreased the risk of MCI development (p = 0.005) compared to those without thyroid disease. Though vascular factors are often attributed to higher mortality and neurodegeneration in African Americans, congestive heart failure, diabetes, high cholesterol, hypertension, diabetes, nor seizures were associated with an increased risk of MCI development. Findings from this study provide formative data to develop targeted interventions for subsets of the African American community, including those with higher educational levels, those with TBI, and those with a history of thyroid disease. While it may not be possible to prevent MCI development, it is possible to modify lifestyle behaviors contributing to these health conditions, such as falls that are often experienced by older adults. Practitioners can increase awareness, knowledge, and resources relevant to clients.

Thyrotropin level and cognitive performance: Baseline results from the ELSA-Brasil Study

BACKGROUND AND AIMS

The role of subtle thyroid alterations, such as subclinical thyroid disease and low/high serum thyrotropin (TSH) within the normal range, on cognitive decline is controversial. The aim of this study was to evaluate the association of serum TSH and subclinical thyroid dysfunction with performance on cognitive tests in a large sample of Brazilian middle-aged adults without overt thyroid disease.

METHODS

In this cross-sectional analysis of the Brazilian Longitudinal Study of Adult Health, we excluded individuals aged 65 years and older, with overt thyroid dysfunction, prevalent stroke, in use of medications that affect thyroid function or that indicate neurologic diseases, and from Asian or indigenous ethnicity. Thyroid status was assessed by serum TSH and free thyroxine (only when the TSH was altered). Individuals were divided according to TSH tertiles and classified according to thyroid function as euthyroidism, subclinical hypothyroidism, or subclinical hyperthyroidism. Cognition was evaluated using delayed word recall test, semantic verbal fluency test, and trail making test version B. The associations of cognitive tests performance with TSH tertiles (using the middle tertile as reference) and thyroid function were investigated using linear regression models, adjusted for an extensive set of possible confounders (sociodemographic characteristics, cardiovascular risk factors, and depression).

RESULTS

The mean age of the 10,362 participants was 49.5±7.4years, 52.3% women. After adjustment for confounders, the first TSH tertile was associate with worse performance on the trail making test (β=-0.05, 95% CI=-0.09; -0.01, p=0.017). When restricting the analysis to the 9769 individuals with TSH within the normal range, the association between TSH and performance on the trail making test remained significant (β=-0.05, 95% CI=-0.09; -0.01, p=0.020) on multiple linear regression. Subclinical thyroid disease was not associated with performance on cognitive tests.

CONCLUSION

Low TSH is associated with poorer performance on an executive function test in middle-aged adults without overt thyroid dysfunction.

Is heart disease a risk factor for low dementia test battery scores in older persons with Down syndrome? Exploratory, pilot study, and commentary

OBJECTIVES

Certain heart conditions and diseases are common in Down syndrome (DS; trisomy 21), but their role in early onset dementia that is prevalent in older adults with DS has not been evaluated. To address this knowledge gap, we conducted a study of risk factors for low neurocognitive/behavioral scores obtained with a published dementia test battery (DTB). Participants were adults with DS living in New York (N = 29; average age 46 years). We asked three questions. 1. Does having any type of heart disease affect the association between DTB scores and chronological age? 2. Does thyroid status affect the association between heart disease and DTB scores? 3. Are the E4 or E2 alleles of apolipoprotein E (APOE) associated with DTB scores or with heart disease?

METHOD

The study was retrospective, pilot, and exploratory. It involved analysis of information in a database previously established for the study of aging in DS. Participants had moderate intellectual disability on average. Information for each person included: gender, age, a single DTB score obtained by combining results from individual subscales of the DTB, the presence or absence of heart disease, thyroid status (treated hypothyroidism or normal), and APOE genotype. Trends were visualized by inspection of graphs and contingency tables. Statistical methods used to evaluate associations included Pearson correlation analysis, Fisher's exact tests (2-tailed), and odds ratio analysis. P values were interpreted at the 95% confidence level without Bonferroni correction. P values >.05<.1 were considered trends.

RESULTS

The negative correlation between DTB scores and age was significant in those with heart disease but not in those without. Heart disease was significantly associated with DTB scores >1 SD below the sample mean; there was a strong association between heart disease and low DTB scores in those with treated hypothyroidism but not in those with normal thyroid status. The APOE genotype was weakly associated with heart disease (E4, predisposing; E2, protective) in males.

CONCLUSIONS

On the basis of the potentially important findings from the present study, large prospective studies are warranted to confirm and extend the observations. In these, particular heart conditions or diseases and other medical comorbidities in individuals should be documented.

Subclinical Thyroid Dysfunction and the Risk of Cognitive Decline: a Meta-Analysis of Prospective Cohort Studies

CONTEXT

Although both overt hyper- and hypothyroidism are known to lead to cognitive impairment, data on the association between subclinical thyroid dysfunction and cognitive function are conflicting.

OBJECTIVE

This study sought to determine the risk of dementia and cognitive decline associated with subclinical thyroid dysfunction among prospective cohorts.

DATA SOURCES

We searched in MEDLINE and EMBASE from inception until November 2014.

STUDY SELECTION

Two physicians identified prospective cohorts that assessed thyroid function and cognitive outcomes (dementia; Mini-Mental State Examination [MMSE]).

DATA EXTRACTION

Data were extracted by one reviewer following standardized protocols and verified by a second reviewer. The primary outcome was dementia and decline in cognitive function was the secondary outcome.

DATA SYNTHESIS

Eleven prospective cohorts followed 16,805 participants during a median followup of 44.4 months. Five studies analyzed the risk of dementia in subclinical hyperthyroidism (SHyper) (n = 6410), six in subclinical hypothyroidism (SHypo) (n = 7401). Five studies analyzed MMSE decline in SHyper (n = 7895), seven in SHypo (n = 8960). In random-effects models, the pooled adjusted risk ratio for dementia in SHyper was 1.67 (95% confidence interval, 1.04; 2.69) and 1.14 (95% confidence interval, 0.84; 1.55) in SHypo vs euthyroidism, both without evidence of significant heterogeneity (I² = 0.0%). The pooled mean MMSE decline from baseline to followup (mean 32 mo) did not significantly differ between SHyper or SHypo vs euthyroidism.

CONCLUSIONS

SHyper might be associated with an elevated risk for dementia, whereas SHypo is not, and both conditions are not associated with faster decline in MMSE over time. Available data are limited, and additional large, high-quality studies are needed.

Serum Thyroid Function, Mortality and Disability in Advanced Old Age: The Newcastle 85+ Study

CONTEXT

Perturbations in thyroid function are common in older individuals but their significance in the very old is not fully understood.

OBJECTIVE

This study sought to determine whether thyroid hormone status and variation of thyroid hormones within the reference range correlated with mortality and disability in a cohort of 85-year-olds.

DESIGN

A cohort of 85-year-old individuals were assessed in their own homes (community or institutional care) for health status and thyroid function, and followed for mortality and disability for up to 9 years.

SETTING AND PARTICIPANTS

Six hundred and forty-three 85-year-olds registered with participating general practices in Newcastle and North Tyneside, United Kingdom.

MAIN OUTCOMES

All-cause mortality, cardiovascular mortality, and disability according to thyroid disease status and baseline thyroid hormone parameters (serum TSH, FT₄, FT₃, and rT₃). Models were adjusted for age, sex, education, body mass index, smoking, and disease count.

RESULTS

After adjustment for age and sex, all-cause mortality was associated with baseline serum rT₃ and FT₃ (both P < .001), but not FT₄ or TSH. After additional adjustment for potential confounders, only rT₃ remained significantly associated with mortality (P = .001). Baseline serum TSH and rT₃ predicted future disability trajectories in men and women, respectively.

CONCLUSIONS

Our study is reassuring that individuals age 85 y with both subclinical hypothyroidism and subclinical hyperthyroidism do not have a significantly worse survival over 9 years than their euthyroid peers. However, thyroid function tests did predict disability, with higher serum TSH levels predicting better outcomes. These data strengthen the argument for routine use of age-specific thyroid function reference ranges.

2016 American Thyroid Association Guidelines for Diagnosis and Management of Hyperthyroidism and Other Causes of Thyrotoxicosis

BACKGROUND

Thyrotoxicosis has multiple etiologies, manifestations, and potential therapies. Appropriate treatment requires an accurate diagnosis and is influenced by coexisting medical conditions and patient preference. This document describes evidence-based clinical guidelines for the management of thyrotoxicosis that would be useful to generalist and subspecialty physicians and others providing care for patients with this condition.

METHODS

The American Thyroid Association (ATA) previously cosponsored guidelines for the management of thyrotoxicosis that were published in 2011. Considerable new literature has been published since then, and the ATA felt updated evidence-based guidelines were needed. The association assembled a task force of expert clinicians who authored this report. They examined relevant literature using a systematic PubMed search supplemented with additional published materials. An evidence-based medicine approach that incorporated the knowledge and experience of the panel was used to update the 2011 text and recommendations. The strength of the recommendations and the quality of evidence supporting them were rated according to the approach recommended by the Grading of Recommendations, Assessment, Development, and Evaluation Group.

RESULTS

Clinical topics addressed include the initial evaluation and management of thyrotoxicosis; management of Graves' hyperthyroidism using radioactive iodine, antithyroid drugs, or surgery; management of toxic multinodular goiter or toxic adenoma using radioactive iodine or surgery; Graves' disease in children, adolescents, or pregnant patients; subclinical hyperthyroidism; hyperthyroidism in patients with Graves' orbitopathy; and management of other miscellaneous causes of thyrotoxicosis. New paradigms since publication of the 2011 guidelines are presented for the evaluation of the etiology of thyrotoxicosis, the management of Graves' hyperthyroidism with antithyroid drugs, the management of pregnant hyperthyroid patients, and the preparation of patients for thyroid surgery. The sections on less common causes of thyrotoxicosis have been expanded.

CONCLUSIONS

One hundred twenty-four evidence-based recommendations were developed to aid in the care of patients with thyrotoxicosis and to share what the task force believes is current, rational, and optimal medical practice.

Patients with chronic insomnia have selective impairments in memory that are modulated by cortisol

Memory impairment is a frequent complaint in insomniacs; however, it is not consistently demonstrated. It is unknown whether memory impairment in insomniacs involves neuroendocrine dysfunction. The participants in this study were selected from the clinical setting and included 21 patients with chronic insomnia disorder (CID), 25 patients with insomnia and comorbid depressive disorder (CDD), and 20 control participants without insomnia. We evaluated spatial working and reference memory, object working and reference memory, and object recognition memory using the Nine Box Maze Test. We also evaluated serum neuroendocrine hormone levels. Compared to the controls, the CID patients made significantly more errors in spatial working and object recognition memory (p < .05), whereas the CDD patients performed poorly in all the assessed memory types (p < .05). In addition, the CID patients had higher levels (mean difference [95% CI]) of corticotrophin-releasing hormone, cortisol (31.98 [23.97, 39.98] μg/l), total triiodothyronine (667.58 [505.71, 829.45] μg/l), and total thyroxine (41.49 [33.23, 49.74] μg/l) (p < .05), and lower levels of thyrotropin-releasing hormone (-35.93 [-38.83, -33.02] ng/l), gonadotropin-releasing hormone (-4.50 [-5.02, -3.98] ng/l) (p < .05), and adrenocorticotropic hormone compared to the CDD patients. After controlling for confounding variables, the partial correlation analysis revealed that the levels of cortisol positively correlated with the errors in object working memory (r = .534, p = .033) and negatively correlated with the errors in object recognition memory (r = -.659, p = .006) in the CID patients. The results suggest that the CID patients had selective memory impairment, which may be mediated by increased cortisol levels.

Phytoestrogen consumption and risk for cognitive decline and dementia: With consideration of thyroid status and other possible mediators

It is predicted that around 20% of the worlds population will be age 60 or above by 2050. Prevalence of cognitive decline and dementia is high in older adults and modifiable dietary factors may be able to reduce risk for these conditions. Phytoestrogens are bioactive plant chemicals found in soy, which have a similarity in structure to natural estradiol (the most abundant circulating estrogen). This structural likeness enables phytoestrogens to interact with estrogen receptors in the brain, potentially affecting cognition. However, findings in this domain are largely inconsistent, with approximately 50% of studies showing positive effects of phytoestrogens on cognition and the other half resulting in null/negative findings. This paper provides an updated review of the relationship between consumption of phytoestrogens and risk for cognitive decline and/or dementia. In particular, possible mediators were identified to explain discrepant findings and for consideration in future research. A case can be made for a link between phytoestrogen consumption, thyroid status and cognition in older age, although current findings in this area are very limited. Evidence suggests that inter-individual variants that can affect phytoestrogen bioavailability (and thus cognitive outcome) include age and ability to breakdown ingested phytoestrogens into their bioactive metabolites. Factors of the study design that must be taken into account are type of soy product, dosage, frequency of dietary intake and type of cognitive test used. Guidelines regarding optimal phytoestrogen dosage and frequency of intake are yet to be determined.

Endocrine Risk Factors for Cognitive Impairment

Cognitive impairment, including Alzheimer's disease and other kinds of dementia, is a major health problem in older adults worldwide. Although numerous investigators have attempted to develop effective treatment modalities or drugs, there is no reasonably efficacious strategy for preventing or recovering from cognitive impairment. Therefore, modifiable risk factors for cognitive impairment have received attention, and the growing literature of metabolic risk factors for cognitive impairment has expanded from epidemiology to molecular pathogenesis and therapeutic management. This review focuses on the epidemiological evidence for the association between cognitive impairment and several endocrine risk factors, including insulin resistance, dyslipidemia, thyroid dysfunction, vitamin D deficiency, and subclinical atherosclerosis. Researches suggesting possible mechanisms for this association are reviewed. The research investigating modifiable endocrine risk factors for cognitive impairment provides clues for understanding the pathogenesis of cognitive impairment and developing novel treatment modalities. However, so far, interventional studies investigating the beneficial effect of the "modification" of these "modifiable risk factors" on cognitive impairment have reported variable results. Therefore, well-designed, randomized prospective interventional studies are needed.

Does low-normal serum TSH level adversely impact cognition in elderly adults and might methimazole therapy improve outcomes?

Serum thyroid stimulating hormone (TSH) levels increase with age. This elevation has been associated with better outcomes in very elderly subjects; however, little is known about the relationship between TSH below the lower limit of the reference range and health-related outcomes. Here, we investigated the association between cognitive impairment or depressive symptoms and low-normal serum TSH (<1.0 μIU/mL, in the reference range) in elderly subjects and whether the use of methimazole in subjects without dementia but with low-normal TSH could affect cognition or depressive symptoms. From 293 healthy adults ≥65 years old with normal TSH included in the sectional phase, only subjects without dementia were prospectively analyzed: 1) TSH ≥1.0 μIU/mL (observation; untreated); 2) TSH <1.0 μIU/mL (observation; untreated); and 3) TSH <1.0 μIU/mL (methimazole therapy). Cognition was assessed, using the Mini Mental State Examination (MMSE) and depressive symptoms (at MMSE ≥ 13) by the Geriatric Depression Scale (GDS). Age >80 years was the sole independent factor associated with dementia (OR=2.89; confidence interval [CI] 1.72-4.86; p<0.01). Prospectively, 93 completed follow-up, with 7.5% (7) receiving methimazole intervention. Untreated subjects with lower TSH showed the greatest declines in MMSE scores during follow-up that was not observed in those with serum TSH ≥1.0 μIU/mL. Lower MMSE score reductions were associated with elderly subjects receiving methimazole. There were no significant changes in depressive symptoms and GDS scores among those with serum TSH <1.0 μIU/mL. In this study, low-normal TSH was not associated with higher prevalence of dementia. However, in elderly subjects without dementia, low TSH was associated with worsening cognition.

Is thyroid status associated with cognitive impairment in elderly patients in China?

BACKGROUND

The relationship between alterations in thyroid function and cognitive deficits has been investigated in several previous studies. Hypo-or hyperthyroidism and, to a lesser extent, subclinical thyroid dysfunction can negatively affect cognitive performance. However, limited data are available on the potential association of thyroid function with mild cognitive impairment (MCI) and Alzheimer's disease (AD) in the elderly Chinese population.

METHODS

In the present study focusing on a population of elderly Chinese individuals ≥ 50 years of age, 77 cognitively normal controls, 64 patients with MCI, and 154 patients diagnosed with AD underwent assessment of thyroid status using thyroid stimulating hormone (TSH), free triiodothyronine (fT3) and free thyroxine (fT4) levels as variables. Cognitive function was evaluated with the aid of comprehensive neuropsychological tests, such as the Mini-Mental State Examination (MMSE) and Memory and Executive Screening (MES).

RESULTS

Overall, 88.1 % of the subjects displayed normal thyroid function, 4.7 % were diagnosed with clinical hypothyroidism, 3.1 % with subclinical hypothyroidism, and 4.1 % with subclinical hyperthyroidism. After adjusting for covariates (age, sex, education years and body mass index), no association was evident between mild cognitive impairment or AD and thyroid dysfunction. However, lower serum TSH was correlated with risk of AD (odds ratio [OR]: 2.78, 95 % confidence interval [95% CI]: 1.11-6.99).

CONCLUSION

Neither hypothyroidism nor subclinical hyperthyroidism was associated with AD and MCI in this population-based elderly Chinese cohort. Our findings need to be confirmed in a longitudinal study.

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

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

Sweet taste receptor signaling network: possible implication for cognitive functioning

Sweet taste receptors are transmembrane protein network specialized in the transmission of information from special "sweet" molecules into the intracellular domain. These receptors can sense the taste of a range of molecules and transmit the information downstream to several acceptors, modulate cell specific functions and metabolism, and mediate cell-to-cell coupling through paracrine mechanism. Recent reports indicate that sweet taste receptors are widely distributed in the body and serves specific function relative to their localization. Due to their pleiotropic signaling properties and multisubstrate ligand affinity, sweet taste receptors are able to cooperatively bind multiple substances and mediate signaling by other receptors. Based on increasing evidence about the role of these receptors in the initiation and control of absorption and metabolism, and the pivotal role of metabolic (glucose) regulation in the central nervous system functioning, we propose a possible implication of sweet taste receptor signaling in modulating cognitive functioning.

Psychiatric and cognitive manifestations of hypothyroidism

PURPOSE OF REVIEW

Overt hypothyroidism has major effects on neuropsychiatric function, but patients with mild hypothyroidism may attribute unrelated neuropsychiatric symptoms to their thyroid condition. This review will summarize data on neuropsychiatric effects of hypothyroidism, and provide guidelines regarding the relationship between hypothyroidism and neuropsychiatric issues, and treatment indications.

RECENT FINDINGS

Clinical investigations and functional imaging studies confirm that overt hypothyroidism is associated with affective and cognitive decrements, largely reversible with treatment. In contrast, subclinical hypothyroidism is not associated with major neuropsychiatric deficits, although studies utilizing sensitive measures show small deficits in memory and executive function. Neuropsychiatric complaints are more common when patients are aware of their thyroid disease, regardless of their thyroid function at the time of testing.

SUMMARY

Neuropsychiatric dysfunction is common in overt hypothyroidism and will improve (perhaps not completely resolve) with therapy. Deficits related to thyroid dysfunction are usually mild in subclinical hypothyroidism, and realistic expectations need to be set regarding symptom reversibility with treatment. Patients with mild hypothyroidism and significant distress related to neuropsychiatric symptoms, most likely, have independent diagnoses that should be evaluated separately.

Standards for thyroid laboratory testing, and cognitive functions after menopause

INTRODUCTION

The aim of the study is to analyze the relationship between normative and non-normative thyroid tests (TSH, TT4, TT3, FT3, FT4, anti-TPO, anti-Tg, AB-TSHR) and the level of cognitive functions in postmenopausal women.

MATERIAL AND METHODS

The study group consisted of 383 women from south-eastern Poland, aged 50-65 years. The cognitive functions were evaluated using a diagnostic instrument - Central Nervous System - Vital Signs (CNS-VS). Blood was collected for determination of the following parameters: TSH, TT4, TT3, FT3, FT4, anti-TPO, anti-Tg, AB-TSHR.

RESULTS

There were significant differences in NCI, executive functions, psychomotor speed, reaction time, complex attention and cognitive flexibility, depending on the normative and non-normative level of TSH. Women whose level of FT3 was at the lower limit of the normal range obtained poorer results in psychomotor speed, while subjects with levels of FT4 below the standard achieved significantly lower scores for this function. The relationship between NCI and cognitive functions, and the normative and non-normative anti-TPO results, showed significant differences in verbal memory, visual memory, processing speed and reaction time. The level of AB-TSHR reported as normal or above the norm significantly differentiated from the results of NCI, processing speed, executive functions, psychomotor speed, complex attention and cognitive flexibility.

CONCLUSIONS

Concentrations of laboratory parameters assessing the thyroid function located within the upper limits of the normal range showed a different relationship with the cognitive performance than concentrations located within the lower limits of the standard.

Treatment with thyroid hormone

Thyroid hormone deficiency can have important repercussions. Treatment with thyroid hormone in replacement doses is essential in patients with hypothyroidism. In this review, we critically discuss the thyroid hormone formulations that are available and approaches to correct replacement therapy with thyroid hormone in primary and central hypothyroidism in different periods of life such as pregnancy, birth, infancy, childhood, and adolescence as well as in adult patients, the elderly, and in patients with comorbidities. Despite the frequent and long term use of l-T4, several studies have documented frequent under- and overtreatment during replacement therapy in hypothyroid patients. We assess the factors determining l-T4 requirements (sex, age, gender, menstrual status, body weight, and lean body mass), the major causes of failure to achieve optimal serum TSH levels in undertreated patients (poor patient compliance, timing of l-T4 administration, interferences with absorption, gastrointestinal diseases, and drugs), and the adverse consequences of unintentional TSH suppression in overtreated patients. Opinions differ regarding the treatment of mild thyroid hormone deficiency, and we examine the recent evidence favoring treatment of this condition. New data suggesting that combined therapy with T3 and T4 could be indicated in some patients with hypothyroidism are assessed, and the indications for TSH suppression with l-T4 in patients with euthyroid multinodular goiter and in those with differentiated thyroid cancer are reviewed. Lastly, we address the potential use of thyroid hormones or their analogs in obese patients and in severe cardiac diseases, dyslipidemia, and nonthyroidal illnesses.

Thyroid disease and cognition

Overt hypothyroidism and thyrotoxicosis are associated with significant decrements in mood and cognitive function, and therapy usually leads to improvement in these symptoms. In contrast, major affective or cognitive dysfunction is not typical of subclinical thyroid disease. Subtle deficits in specific cognitive domains (primarily working memory and executive function) likely exist in subclinical hypothyroidism and thyrotoxicosis, but these are unlikely to cause major problems in most patients. Patients with mild thyroid disease and significant distress related to mood or cognition most likely have independent diagnoses that should be evaluated and treated separately.

An update on subclinical hypothyroidism and subclinical hyperthyroidism

Subclinical thyroid dysfunction is characterized by normal levels of peripheral thyroid hormone, paired with a TSH level that is either lower than (subclinical hyperthyroidism) or higher than (subclinical hypothyroidism) the normal laboratory reference range. Slight shifts in peripheral hormone levels result in significant serum TSH changes. The exact upper limit of normal TSH and the management of subclinical hypothyroidism are still controversial. For those with TSH between high upper limit of normal and 10 mIU/L, the authors suggest selective use of thyroxine therapy. The authors agree with the general consensus in favor of therapy for those with serum TSH levels above 10 mIU/L. This recommendation is compatible with guidelines of American Thyroid Association and American Association of Clinical Endocrinologists. For subclinical hyperthyroidism persistent serum TSH <0.1 mIU/L should be treated particularly if the etiology is nodular toxic goiter. For serum TSH between 0.1 mIU/L and lower limit of normal, serum TSH co-morbidities such as cardiac risk factors and osteoporosis may favor therapy.

Lower-but-normal serum TSH level is associated with the development or progression of cognitive impairment in elderly: Korean Longitudinal Study on Health and Aging (KLoSHA)

CONTEXT

The association between subclinical hyperthyroidism and the risk of dementia has been validated in several studies. However, the effect of thyroid function within reference range on the risk of cognitive dysfunction including mild cognitive impairment (MCI) and dementia is still unclear.

OBJECTIVE

Our aim was to investigate the association between thyroid function and the risk of MCI and dementia in euthyroid elderly subjects.

DESIGN, SETTING, AND PARTICIPANTS

We conducted a population-based prospective study as a part of the Korean Longitudinal Study on Health and Aging. A total of 313 participants who were euthyroid and nondemented at baseline and completed cognitive function tests at a 5-year follow-up evaluation (mean age 72.5 ± 6.9 y) were analyzed in the present study.

MAIN OUTCOME MEASURE

Baseline thyroid function was compared according to the development of MCI or dementia during the study period. Binary logistic regression analysis was performed to investigate the independent association between thyroid function and cognitive impairment.

RESULTS

At baseline evaluation, 237 subjects were cognitively normal, and 76 subjects had MCI. Diagnoses of cognitive function in 259 subjects remained unchanged or improved during the study period (nonprogression group), whereas 54 subjects showed progression of cognitive impairment to MCI or dementia (progression group). In the progression group, baseline serum TSH levels were lower than those in nonprogression group. Baseline serum free T₄ levels were not significantly different between these two groups. The association between lower baseline serum TSH levels and the development of MCI or dementia was maintained after adjustment for conventional baseline risk factors.

CONCLUSIONS

Lower serum TSH level within the reference range was independently associated with the risk of cognitive impairment including MCI and dementia in elderly subjects.

Circulating biomarkers that predict incident dementia

Dementia is currently diagnosed based on clinical symptoms and signs, but significant brain damage has already occurred by the time a clinical diagnosis of dementia is made, and it is increasingly recognized that this may be too late for any effective intervention. It would therefore be of great public health and preventive value to define a variety of biomarkers that could permit early detection of persons at a higher risk for developing dementia, and specifically dementia due to Alzheimer's disease. Nevertheless, for the purpose of large-scale screening, circulating biomarkers are more appropriate because they are less invasive than lumbar puncture, less costly than brain amyloid imaging and can be easily assessed repeatedly in a primary care clinic setting. In this brief review we will review a number of candidate molecules implicated as possible predictors of dementia risk. These candidates include markers of vascular injury, metabolic and inflammatory states, amyloid and tau pathway markers, measures of neural degeneration and repair efforts, and other molecules that might contribute to anatomical and functional changes characteristic of dementia and Alzheimer's disease.

The role of thyroid hormones as inductors of oxidative stress and neurodegeneration

Reactive oxygen species (ROS) are oxidizing agents amply implicated in tissue damage. ROS production is inevitably linked to ATP synthesis in most cells, and the rate of production is related to the rate of cell respiration. Multiple antioxidant mechanisms limit ROS dispersion and interaction with cell components, but, when the balance between ROS production and scavenging is lost, oxidative damage develops. Many traits of aging are related to oxidative damage by ROS, including neurodegenerative diseases. Thyroid hormones (THs) are a major factor controlling metabolic and respiratory rates in virtually all cell types in mammals. The general metabolic effect of THs is a relative acceleration of the basal metabolism that includes an increase of the rate of both catabolic and anabolic reactions. THs are related to oxidative stress not only by their stimulation of metabolism but also by their effects on antioxidant mechanisms. Thyroid dysfunction increases with age, so changes in THs levels in the elderly could be a factor affecting the development of neurodegenerative diseases. However, the relationship is not always clear. In this review, we analyze the participation of thyroid hormones on ROS production and oxidative stress, and the way the changes in thyroid status in aging are involved in neurodegenerative diseases.