Subclinical hypothyroidism, mood, and cognition in older adults: a review

Mapping Thyroid Hormone Action in the Human Brain

Background: Normal brain development, mood, and cognitive functions depend on thyroid hormone (TH) action. However, little is known about how TH mediates its actions in the human brain. This is due to limited access to human brains deprived of TH during fetal and early postnatal life, as well as from adults with altered thyroid status. One way to partially bypass these limitations is by using magnetic resonance imaging and spectroscopy, two neuroimaging techniques that provide detailed, noninvasive information on human brain structure and function. Another way is using human-induced pluripotent stem cell (hiPSCs)-derived three-dimensional in vitro systems, known as brain organoids, which allow for the study of fundamental aspects of the early stages of human brain development. Summary: This narrative review focuses on neuroimaging and brain organoid studies. Neuroimaging of human brains performed in individuals with different thyroid conditions provides information on the volume, myelination, blood flow, neural activity, and connectivity of different areas. Such studies show that suboptimal thyroid status can impact human brain development and its normal function throughout life. This is true not only for patients with sporadic congenital hypothyroidism, during pregnancy or early after birth, but also for adult patients with hypo- or hyperthyroidism, patients carrying mutations that manifest as impaired sensitivity to TH, and even for normal individuals during aging. Studies using brain organoids generated from hiPSCs of healthy individuals or patients with thyroid genetic conditions provide insights into how TH can impact the early development of the human cerebral cortex. Conclusions: The developmental alterations in children born to mothers with different degrees of gestational hypothyroidism or who developed hypothyroidism early in life are remarkable, affecting multiple brain regions and pathways, including the cerebral cortex, hippocampus, cerebellum, interhemispheric and corticospinal tracts, and associative nuclei. The data connecting such changes to poor neurological outcomes in adult patients with hypothyroidism represent an objective link between thyroid-specific functional brain alterations and behavior. Growing brain organoids require TH, which is critical for human neurogenesis and oligodendrogenesis. These models have proven useful in screening drugs with potential therapeutic effects for patients with genetic thyroid diseases.

Impaired T3 uptake and action in MCT8-deficient cerebral organoids underlie Allan-Herndon-Dudley syndrome

Patients with mutations in the thyroid hormone (TH) cell transporter monocarboxylate transporter 8 (MCT8) gene develop severe neuropsychomotor retardation known as Allan-Herndon-Dudley syndrome (AHDS). It is assumed that this is caused by a reduction in TH signaling in the developing brain during both intrauterine and postnatal developmental stages, and treatment remains understandably challenging. Given species differences in brain TH transporters and the limitations of studies in mice, we generated cerebral organoids (COs) using human induced pluripotent stem cells (iPSCs) from MCT8-deficient patients. MCT8-deficient COs exhibited (i) altered early neurodevelopment, resulting in smaller neural rosettes with thinner cortical units, (ii) impaired triiodothyronine (T3) transport in developing neural cells, as assessed through deiodinase-3-mediated T3 catabolism, (iii) reduced expression of genes involved in cerebral cortex development, and (iv) reduced T3 inducibility of TH-regulated genes. In contrast, the TH analogs 3,5-diiodothyropropionic acid and 3,3',5-triiodothyroacetic acid triggered normal responses (induction/repression of T3-responsive genes) in MCT8-deficient COs, constituting proof of concept that lack of T3 transport underlies the pathophysiology of AHDS and demonstrating the clinical potential for TH analogs to be used in treating patients with AHDS. MCT8-deficient COs represent a species-specific relevant preclinical model that can be utilized to screen drugs with potential benefits as personalized therapeutics for patients with AHDS.

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.

Cerium Oxide Nanoparticles Protect Cortical Astrocytes from Oxygen-Glucose Deprivation through Activation of the Ca2+ Signaling System

Most of the works aimed at studying the cytoprotective properties of nanocerium are usually focused on the mechanisms of regulation of the redox status in cells while the complex effects of nanocerium on calcium homeostasis, the expression of pro-apoptotic and protective proteins are generally overlooked. There is a problem of a strong dependence of the effects of cerium oxide nanoparticles on their size, method of preparation and origin, which significantly limits their use in medicine. In this study, using the methods of molecular biology, immunocytochemistry, fluorescence microscopy and inhibitory analysis, the cytoprotective effect of cerium oxide nanoparticles obtained by laser ablation on cultured astrocytes of the cerebral cortex under oxygen-glucose deprivation (OGD) and reoxygenation (ischemia-like conditions) are shown. The concentration effects of cerium oxide nanoparticles on ROS production by astrocytes in an acute experiment and the effects of cell pre-incubation with nanocerium on ROS production under OGD conditions were studied. The dose dependence for nanocerium protection of cortical astrocytes from a global increase in calcium ions during oxygen-glucose deprivation and cell death were demonstrated. The concentration range of cerium oxide nanoparticles at which they have a pro-oxidant effect on cells has been identified. The effect of nanocerium concentrations on astrocyte preconditioning, accompanied by increased expression of protective proteins and limited ROS production induced by oxygen-glucose deprivation, has been investigated. In particular, a correlation was found between an increase in the concentration of cytosolic calcium under the action of nanocerium and the suppression of cell death. As a result, the positive and negative effects of nanocerium under oxygen-glucose deprivation and reoxygenation in astrocytes were revealed at the molecular level. Nanocerium was found to act as a "double-edged sword" and to have a strictly defined concentration therapeutic "window".

Axonal T3 uptake and transport can trigger thyroid hormone signaling in the brain

The development of the brain, as well as mood and cognitive functions, are affected by thyroid hormone (TH) signaling. Neurons are the critical cellular target for TH action, with T3 regulating the expression of important neuronal gene sets. However, the steps involved in T3 signaling remain poorly known given that neurons express high levels of type 3 deiodinase (D3), which inactivates both T4 and T3. To investigate this mechanism, we used a compartmentalized microfluid device and identified a novel neuronal pathway of T3 transport and action that involves axonal T3 uptake into clathrin-dependent, endosomal/non-degradative lysosomes (NDLs). NDLs-containing T3 are retrogradely transported via microtubules, delivering T3 to the cell nucleus, and doubling the expression of a T3-responsive reporter gene. The NDLs also contain the monocarboxylate transporter 8 (Mct8) and D3, which transport and inactivate T3, respectively. Notwithstanding, T3 gets away from degradation because D3's active center is in the cytosol. Moreover, we used a unique mouse system to show that T3 implanted in specific brain areas can trigger selective signaling in distant locations, as far as the contralateral hemisphere. These findings provide a pathway for L-T3 to reach neurons and resolve the paradox of T3 signaling in the brain amid high D3 activity.

Association of Hypothyroidism and the Risk of Cognitive Dysfunction: A Meta-Analysis

Objectives: The purpose of this meta-analysis was to assess whether there is an association between hypothyroidism and the risk of cognitive dysfunction. Methods: PubMed, Cochrane Library, and Embase were searched for relevant studies published from database inception to 4 May 2022, using medical subject headings (MeSHs) and keywords. Results: Eight studies involving 1,092,025 individuals were included, published between 2010 and 2021. The pooled analysis showed that there was no association between hypothyroidism and cognitive dysfunction (OR = 1.13, 95% CI = 0.84−1.51, p = 0.426), including both all-cause dementia (OR = 1.04, 95% CI = 0.76−1.43, p = 0.809) and cognitive impairment (OR = 1.50, 95% CI = 0.68−3.35, p = 0.318). Neither overt hypothyroidism (OR = 1.19, 95% CI = 0.70−2.02, p = 0.525) nor subclinical hypothyroidism (OR = 1.04, 95% CI = 0.73−1.48, p = 0.833) was associated with cognitive dysfunction. Neither prospective cohort (OR = 1.08, 95% CI = 0.77−1.51, p = 0.673) nor cross-sectional studies (OR = 1.23, 95% CI = 0.63−2.42, p = 0.545) had any effect on the association. Interestingly, the risk of cognitive dysfunction was significantly increased in the group not adjusted for vascular comorbidity (OR = 1.47, 95% CI = 1.07−2.01, p = 0.017), while it was reduced in the adjusted group (OR =0.82, 95% CI = 0.79−0.85, p < 0.001). Conclusions: This meta-analysis shows that hypothyroidism was associated with a reduced risk of cognitive dysfunction after adjustment for vascular-disease comorbidities. More prospective observational studies are needed in the future to investigate the relationship between hypothyroidism and cognitive dysfunction.

The prevalence and clinical correlates of suicide attempts in comorbid subclinical hypothyroidism in patients with never-treated major depressive disorder in China

BACKGROUND

Previous studies have emphasized the possible association between subclinical hypothyroidism (SCH) and major depressive disorder (MDD). This study aimed to further investigate suicide attempts and their clinical correlates in MDD patients with comorbid SCH.

METHODS

This cross-sectional study recruited 1706 eligible MDD outpatients. The Hamilton Depression Rating Scale (HAMD), Hamilton Anxiety Rating Scale (HAMA), Positive and Negative Syndrome Scale (PANSS) and Clinical Global Impression of Severity Scale (CGI-S) were applied to evaluate mental status. Fasting blood samples were collected to examine thyroid function. SCH was defined as thyroid stimulating hormone (TSH) > 8 mIU/L with normal free thyroxine levels.

RESULTS

The prevalence of suicide attempts in the SCH group (51.7 %) was significantly higher than that in the non-SCH group (15.4 %; p < 0.001). Logistic regression showed that patients with comorbid SCH were 1.81 times more likely to have attempted suicide as compared with those without (p = 0.001). Among those with TSH > 8 mIU/L, patients with severe anxiety were 3.57 times more likely to attempt suicide compared with those without (p < 0.01). Logistic regression also showed that the CGI-S score (p < 0.001) was independently associated with suicide attempts, while TSH level was not.

CONCLUSIONS

SCH comorbidity may pose a specific hazard in MDD patients due to increased suicide attempts. Exhibiting severe anxiety, overall severity of depressive and psychotic symptoms, but not TSH levels, may be independently correlated with suicide attempts in MDD patients with TSH > 8 mIU/L.

Peripheral Markers of Depression

Major Depressive Disorder (MDD) is a leading cause of disability worldwide, creating a high medical and socioeconomic burden. There is a growing interest in the biological underpinnings of depression, which are reflected by altered levels of biological markers. Among others, enhanced inflammation has been reported in MDD, as reflected by increased concentrations of inflammatory markers-C-reactive protein, interleukin-6, tumor necrosis factor-α and soluble interleukin-2 receptor. Oxidative and nitrosative stress also plays a role in the pathophysiology of MDD. Notably, increased levels of lipid peroxidation markers are characteristic of MDD. Dysregulation of the stress axis, along with increased cortisol levels, have also been reported in MDD. Alterations in growth factors, with a significant decrease in brain-derived neurotrophic factor and an increase in fibroblast growth factor-2 and insulin-like growth factor-1 concentrations have also been found in MDD. Finally, kynurenine metabolites, increased glutamate and decreased total cholesterol also hold promise as reliable biomarkers for MDD. Research in the field of MDD biomarkers is hindered by insufficient understanding of MDD etiopathogenesis, substantial heterogeneity of the disorder, common co-morbidities and low specificity of biomarkers. The construction of biomarker panels and their evaluation with use of new technologies may have the potential to overcome the above mentioned obstacles.

Thyroid gland and brain: Enigma of Hashimoto's encephalopathy

The versatile clinical manifestations of the Hashimoto's chronic autoimmune thyroiditis often include psycho-neurological disorders. Although hypothyroidism disturbs significantly the ontogenesis and functions of central nervous system, causing in severe cases of myxedema profound impairment of cognitive abilities and even psychosis, the behavioral, motor and other psychoneurological disorders accompany euthyroid and slightly hypothyroid cases and periods of Hashimoto's disease as well, thus constituting the picture of so called "Hashimoto's encephalopathy". The entity, although discussed and explored for more than 50 years since its initial descriptions, remains an enigma of thyroidology and psychiatry, because its etiology and pathogenesis are obscure. The paper describes the development of current views on the role of thyroid in ontogeny and functions of brain, as well as classical and newest ideas on the etiology and pathogenesis of Hashimot's encephalopathy. The synopsis of the world case reports and research literature on this disorder is added with authors' own results obtained by study of 17 cases of Hashimoto's thyroiditis with schizophrenia-like clinical manifestations. The relation of the disease to adjuvant-like etiological factors is discussed. Three major mechanistic concepts of Hashimoto's encephalopathy are detailed, namely cerebral vasculitis theory, hormone dysregulation theory and concept, explaining the disease via direct action of the autoantibodies against various thyroid (thyroperoxidase, thyroglobulin, and TSH-receptor) and several extrathyroid antigens (alpha-enolase and other enzymes, gangliosides and MOG-protein, onconeuronal antigens) - all of them expressed in the brain. The article demonstrates that all above mentioned concepts intermingle and prone to unification, suggesting the unified scheme of pathogenesis for the Hashimoto's encephalopathy. The clinical manifestations, criteria, forms, course, treatment and prognosis of Hashimoto's encephalopathy and its comorbidity to other diseases - are also discussed in brief. The relation between Hashimoto's encephalopathy and non-vasculitis autoimmune encephalomyelitides of paraneoplastic and non-paraneoplastic origin is emphasized [1 figure, bibliography - 200 references].

Association between subclinical hypothyroidism and depression: an updated systematic review and meta-analysis

BACKGROUND

Although depression is associated with changes in the hypothalamic-pituitary-thyroid axis, its relationship with subclinical hypothyroidism (SCH) is controversial. To date, there is a lack of data on the improvement of depressive symptoms with levothyroxine therapy among individuals with coexistent SCH.

METHODS

We conducted a meta-analysis to evaluate the association between SCH and depression including 1) the prevalence of depression in SCH (with a sub-analysis of the geriatric cohort), 2) thyroid stimulating hormone (TSH) level among patients with depression and 3) the effect of levothyroxine therapy among patients with SCH and coexistent depression.

RESULTS

In a pooled analysis of 12,315 individuals, those with SCH had higher risk of depression than euthyroid controls (relative risk 2.35, 95% confidence intervals [CI], 1.84 to 3.02; p < 0.001). Geriatric cohort with SCH had a 1.7-fold higher risk of depression compared with healthy controls (odds ratio 1.72, CI, 1.10 to 2.70; p = 0.020). There was no difference in the mean TSH level between individuals with depression and healthy controls (2.30 ± 1.18 vs. 2.13 ± 0.72 mIU/L, p = 0.513). In individuals with SCH and coexistent depression, levothyroxine therapy was neither associated with improvement in the Beck Depression Inventory scoring (pooled d + = - 1.05, CI -2.72 to 0.61; p = 0.215) nor Hamilton Depression Rating Scale (pooled d + = - 2.38, CI -4.86 to 0.10; p = 0.060).

CONCLUSION

SCH has a negative impact on depression. Early and routine screening of depression is essential to prevent morbidity and mortality. However, the use of levothyroxine among patients with SCH and coexistent depression needs to be individualized.

Effects of Shuganjianpihuatanxingqi decoction on mild subclinical hypothyroidism: A SPIRIT compliant randomized controlled trial study protocol

INTRODUCTION

Mild subclinical hypothyroidism (SCH) can cause depression, fatigue, cognitive dysfunction, or other hypothyroid symptoms, and even progress to hypothyroidism. The treatment of mild SCH is controversial. Shuganjianpihuatanxingqi decoction (SD) is a frequently prescribed Chinese herbal medicine in patients with mild SCH. However, scientific evidence is needed to confirm the therapeutic effect of SD.

METHODS AND ANALYSIS

This study is a randomized, double-blind, and controlled clinical trial. A total of 228 participants with the diagnosis of mild SCH will be randomly assigned to the SD or placebo group in a ratio of 1:1. Participants will receive treatment for 12 weeks and undergo 12-month follow-up. The primary outcome measure is the thyroid-stimulating hormone level, and secondary outcomes will be the differences in the results of Thyroid-related Quality of Life Questionnaire, blood lipids, and Traditional Chinese Medicine Symptom Score Scale between baseline and at 12 weeks after intervention.

ETHICS AND DISSEMINATION

The study has been approved by Guang'anmen Hospital of China Academy of Chinese Medical Sciences (no.2018-005-ky-01). The trial results will be published via peer-reviewed journals and the Clinical Research Information Service.

TRIAL REGISTRATION NUMBER

ChiCTR1800015781 (approval date: 20 April 2018).

Thyroid disease symptoms during early pregnancy do not identify women with thyroid hypofunction that should be treated

OBJECTIVE

To evaluate whether women during early pregnancy with "hypothyroidism" symptoms are at risk of biochemically defined hypothyroidism. The 2017 Guidelines of the American Thyroid Association (ATA) recommend case-finding on the basis of symptoms to identify these women during pregnancy, while evidence is lacking.

DESIGN

Construct validation of a thyroid hypofunction symptom checklist during the first trimester of pregnancy comparing high scores with biochemically defined hypothyroidism.

PATIENTS

A total of 2198 healthy pregnant women from an iodine-sufficient area in 2013-2014.

MEASUREMENTS

Completion of a draft questionnaire with "classical" symptoms of hypothyroidism at 12 weeks of gestation. The 2.5th and 97.5th percentiles of TSH and fT4 during pregnancy in TPO-Ab-negative (<35 kU/L) women were used to define euthyroid women and those with overt (clinical) and subclinical hypothyroidism. The prevalence of overt (subclinical) hypothyroidism was compared between women with high symptom scores and those with low symptom scores.

RESULTS

According to fT4 and TSH cut-offs (0.23-4.0 mIU/L and 11.5-18.0 pmol/L, respectively), there were 15 women with "to treat hypofunction" (overt hypothyroidism or TSH >10 mIU/L) and 68 women with subclinical hypothyroidism. Questionnaire construct validation revealed a 12-item hypothyroid checklist with normally distributed scores. The cut-off indicating high scores of OH was set at 1 SD > mean. Women with high symptom scores did not present more often with biochemically defined thyroid hypofunction.

CONCLUSION

This study does not support the ATA recommendation that pregnant women who require levothyroxine therapy can be identified by case-based screening of women with symptoms of thyroid disease.

Subclinical Hypothyroidism - Whether and When To Start Treatment?

Subclinical hypothyroidism represents a state with increased values of thyroid stimulating hormone (TSH) and normal values of thyroxine (T4) and triiodothyronine (T3). The disorder is asymptomatic, and the diagnosis is made based on the results of laboratory findings when the level of TSH reaches values above 4.0 mU/l. It is still subject to debate whether patients with subclinical hypothyroidism are at increased risk of cardiovascular disease, neuropsychiatric and neuromuscular disorders. Studies have shown that the appearance of general symptoms and complications are more common in patients whose values of TSH are above 10 mU/l. Therefore, the initiation of therapy with levothyroxine, which is the foundation of substitution therapy, is advised in patients whose TSH is >10 mU/l. As for patients whose values of TSH are from 4.0 to 10.0 mU/l and who make up 90% of the patients with subclinical hypothyroidism, further research is needed to determine the effects of the disorder and levothyroxine therapy on the health. Until then, the introduction of the substitution therapy in patients with TSH which is <10 mU/l should be considered in the case of the presence of general symptoms, anti-thyroid antibodies, increased lipids and other risk factors, goitre, pregnancy, ovarian dysfunction and infertility.

Thyroid Function in Aging: A Discerning Approach

Thyroid disease, increasingly common among the general population, is also rising among the elderly, which, given that the global population is aging, constitutes a serious public health issue that needs to be urgently addressed. The most common thyroid disease in younger and older individuals alike is hypothyroidism, including subclinical (SCH) and overt disease. Since TSH tends to increase with age due to intrinsic changes of thyroid metabolism and the gradual resetting of the hypothalamic-pituitary-thyroid axis, the diagnosis of "true" hypothyroidism is challenging, another difficulty being distinguishing disease-specific from aging-associated clinical symptoms. Hypothyroidism in the elderly may cause or exacerbate macrocytic anemia, hypercholesterolemia and kidney dysfunction, therefore careful clinical and biochemical control is necessary. Meanwhile, as an increase of TSH in the old and very old has been associated with longevity, a resetting of the TSH normal range according to age is strongly required before any diagnosis is made and treatment is implemented. Levothyroxine, which remains the treatment of choice, should be initiated in the old at TSH>10 mIU/l, starting with 25 μg/daily followed by cautious upward titration. Recent data (the TRUST study) revealed that treatment of SCH in the elderly does not improve hypothyroid symptoms and the tiredness score when compared with a placebo group. Hyperthyroidism is associated with increased mortality in the aged, this dependent upon type and adequacy of treatment. Treatment should be seriously considered in older patients who have endogenous subclinical hyperthyroidism with a TSH between 0.1 and 0.4 mIU/L, with regular monitoring being strongly advised.

Biomarkers for depression: recent insights, current challenges and future prospects

A plethora of research has implicated hundreds of putative biomarkers for depression, but has not yet fully elucidated their roles in depressive illness or established what is abnormal in which patients and how biologic information can be used to enhance diagnosis, treatment and prognosis. This lack of progress is partially due to the nature and heterogeneity of depression, in conjunction with methodological heterogeneity within the research literature and the large array of biomarkers with potential, the expression of which often varies according to many factors. We review the available literature, which indicates that markers involved in inflammatory, neurotrophic and metabolic processes, as well as neurotransmitter and neuroendocrine system components, represent highly promising candidates. These may be measured through genetic and epigenetic, transcriptomic and proteomic, metabolomic and neuroimaging assessments. The use of novel approaches and systematic research programs is now required to determine whether, and which, biomarkers can be used to predict response to treatment, stratify patients to specific treatments and develop targets for new interventions. We conclude that there is much promise for reducing the burden of depression through further developing and expanding these research avenues.

Thyroid Function Variations Within the Reference Range Do Not Affect Quality of Life, Mood, or Cognitive Function in Community-Dwelling Older Men

BACKGROUND

Variations in thyroid function within the laboratory reference range have been associated with a number of clinical outcomes. However, quality of life, mood, and cognitive function have not been extensively studied, and it is not clear whether mild variations in thyroid function have major effects on these neurocognitive outcomes.

METHODS

Data were analyzed from the Osteoporotic Fractures in Men (MrOS) Study, a cohort of community-dwelling men aged 65 years and older in the United States. A total of 539 participants who were not taking thyroid medications and had age-adjusted TSH levels within the reference range underwent detailed testing of quality of life, mood, and cognitive function at baseline. The same quality of life, mood, and cognitive outcomes were measured again in 193 of the men after a mean follow-up of 6 years. Outcomes were analyzed using thyrotropin (TSH) and free thyroxine (FT4) levels as continuous independent variables, adjusting for relevant covariates.

RESULTS

At baseline, there were no associations between TSH or FT4 levels and measures of quality of life, mood, or cognition in the 539 euthyroid men. Baseline thyroid function did not predict changes in these outcomes over a mean of 6 years in the 193 men in the longitudinal analysis.

CONCLUSIONS

Variations in thyroid function within the age-adjusted laboratory reference range are not associated with variations in quality of life, mood, or cognitive function in community-dwelling older men.

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.

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.

Antidepressant behavior in thyroidectomized Wistar rats is induced by hippocampal hypothyroidism

Thyroidectomy is a surgical procedure indicated in cases of several maligned or benign thyroid diseases, thus, the aim of our study was to verify how the hypothyroidism induced by thyroidectomy influences behavioral parameters and its relation to thyroid hormones metabolism and neurogenesis at hippocampus. For this purpose, Adult male Wistar rats underwent to thyroidectomy to induce hypothyroidism. Behavioral tests, the thyroid profile and hippocampal gene expression were evaluated in control and in thyroidectomized animals. It was observed that thyroidectomized group had a significant increasing in serum thyroid-stimulating hormone (TSH) and a decreasing in thyroxine (T4) levels as well as in triiodothyronine (T3) serum level. It was also observed reduction of the monocarboxylate transporter 8 (Mct8), thyroid hormone receptor alfa (Trα1), deiodinase type 2 (Dio2), ectonucleotide pyrophosphatase/phosphodiesterase 2 (Enpp2) and brain-derived neurotrophic factor (Bdnf) mRNA expression in hippocampus of thyroidectomized animals. In the forced swimming test, it was verified that thyroidectomy promotes a decrease in time of immobility and climbing when compared with the control group. In summary, we demonstrated that antidepressant behavior in thyroidectomized Wistar rats is induced by hippocampal hypothyroidism. This effect could be associated to an impaired neuronal activity in acute stress response as it is observed in forced swimming paradigm.

Levothyroxine treatment of mild subclinical hypothyroidism: a review of potential risks and benefits

Subclinical hypothyroidism (SCH) is defined as elevated thyroid stimulating hormone (TSH) with normal levels of free triiodothyronine (FT3) and free thyroxine (FT4). SCH is further classified into a milder condition with TSH levels between 4.0 and 10.0 milli-international units (mIU)/l (mild-SCH) and a severe form with TSH >10.0 mIU/l (severe-SCH). SCH is a common problem (prevalence is greater in women than men), which increases further with increasing age and TSH levels. Even though the risk of progression to overt hypothyroidism is higher in patients with severe-SCH, the risk is also significant in patients having mild-SCH; it has been suggested that every twofold rise in serum TSH would increase the risk from 1 to 4%, which further increases to 38% if thyroid antibodies are positive. Current data have shown increased cardiovascular risk in patients with mild-SCH and have demonstrated some benefits of levothyroxine treatment in reducing these events. However, evidence on the association of mild-SCH and musculoskeletal system, cognitive dysfunction, mood disorders, dyslipidaemia, diabetes and goitre is conflicting. Similarly, the discussion regarding the exact upper limit of normal for serum TSH remains controversial. The data have also shown increased risk of adverse pregnancy outcomes in patient with mild-SCH, with some benefits of thyroxine treatment. The recent available guidelines related to management of patients with serum TSH <10 mIU/l have suggested decisions should be made taking into account the age of the patient, associated risk factors and comorbid conditions. This chronicle review assesses current evidence regarding the risks associated and the recommendations related to benefits of levothyroxine treatment in patients having mild-SCH.

Subclinical hypothyroidism and cognitive function in people over 60 years: a systematic review and meta-analysis

Subclinical hypothyroidism (SCH), defined as elevated thyroid stimulating hormone (TSH) and normal thyroid hormone levels, and cognitive impairment are both common in older people. While the relation between overt hypothyroidism and cognitive impairment is well established, data on the association between SCH and cognitive impairment are conflicting. This systematic review and meta-analysis was performed to assess available evidence on the association of SCH with cognition in community dwelling, relatively healthy older adults. PubMed, EMBASE, Web of Science, COCHRANE, CINAHL, PsycINFO, and Academic Search Premier (January 1966 to April 1, 2015) were searched without language restrictions, as were references of key articles, for studies on the association between SCH and cognition in older adults (>60 years). These studies were reviewed by two independent reviewers according to predefined criteria for eligibility and methodological quality, and data were extracted using standardized forms. Of the 844 reports initially identified, 270 remained after exclusion of duplicates. Of the 270, 15 studies comprising 19,944 subjects, of whom 1,199 had subclinical hypothyroidism were included. Data from the 15 studies was pooled, and meta-analyzed cross-sectionally for global cognition [assessed by Mini-Mental State Examination (MMSE)], executive function, and memory, using random effects models. Pooled effect size (ES) for MMSE was −0.01 (95% CI −0.09, 0.08), with heterogeneity (I²) of 55.1%. Pooled ES was < 0.001 (95% CI −0.10, 0.09) for executive function (I² = 13.5%), and 0.01 (95% CI −0.12, 0.14) for memory (I² = 46.9%). In addition, prospective analysis including four studies showed pooled ES of 0.033 (95% CI −0.001 − 0.067) for MMSE (I² < 0.001%), indicating that subclinical hypothyroidism was not significantly associated with accelerated cognitive decline. This systematic review and meta-analysis provides no evidence that supports an association between SCH and cognitive impairment in relatively healthy older adults.

Thyroid hormones are associated with longitudinal cognitive change in an urban adult population

Recent evidence indicates that thyroid hormones may be closely linked to cognition among adults. We investigated associations between thyroid hormones and longitudinal cognitive change, within and outside of reference ranges, stratifying by sex and race. This longitudinal study used data from the Healthy Aging in Neighborhoods of Diversity Across the Lifespan study, set in Baltimore City, MD, 2004-2013, on adults aged 30-64 years at baseline visit, with a length of follow-up between visits 1 and 2 ranging from <1 to 8 years; mean ± standard deviation: 4.64 ± 0.93. The final analytic sample sizes ranged from 1486 to 1602 participants with 1.6-1.7 visits per participant (total visits: 2496-2757), depending on the cognitive test. Eleven cognitive test scores spanning domains of learning or memory, language or verbal, attention, visuospatial and/or visuoconstruction, psychomotor speed, executive function, and mental status were used. Mixed-effects regression models were conducted, interacting time of follow-up with several thyroid exposures. Whites performed better than African Americans, with only 4 cognitive test scores of 11 declining significantly over time. Importantly, above reference range thyroid stimulating hormone (vs. reference range, thyroid stimulating hormone, above reference range [TSHarr]) was linked to faster rates of decline on the digits span backwards test, reflecting working memory (TSHarr × time γ ± standard error: -0.14 ± 0.05, p = 0.006) and clock-command, at test of visuospatial and/or visuoconstruction abilities (TSHarr × Time γ ± standard error: -0.10 ± 0.04, p = 0.004). The latter finding was replicated when comparing normal thyroid function to "subclinical hypothyroidism". Within-reference ranges, a higher thyroid stimulating hormone was related to faster decline on the clock-command test scores in women. In sum, higher baseline thyroid stimulating hormone was associated with faster cognitive decline over-time among urban US adults, specifically in domains of working memory and visuospatial and/or visuoconstruction abilities.

Vitamin D and chronic hepatitis C: effects on success rate and prevention of side effects associated with pegylated interferon-α and ribavirin

Chronic hepatitis C (CHC) is one of the most common causes of liver diseases worldwide, affecting 3% of the world population and 3 to 4 million people acquire new infection annually. Despite the recent introduction of novel antiviral drugs for the treatment of CHC, these drugs are expensive and the access to them is not an option for many patients. Hence, the traditional therapy by pegylated interferon-α (Peg-IFN-α) and ribavirin may still have a role in the clinical management of CHC especially in developing countries. However, this standard therapy is associated with several severe extra-hepatic side effects and the most common adverse events are hematological abnormalities and thyroid disorders and they could result in dose reduction and/or termination of therapy. Vitamin D has been shown to be a key regulatory element of the immune system, and its serum concentrations correlate with the severity of liver damage and the development of liver fibrosis/cirrhosis. Furthermore, supplementation with vitamin D with Peg-IFN-α based therapy for the treatment of CHC could be beneficial in increase the response rate to Peg-INF-α based therapy. Vitamin D has also been shown to regulate the thyroid functions and the process of erythropoiesis. This review appraises the data to date researching the role of vitamin D during the treatment of CHC and the potential role of vitamin D in preventing/treating Peg-IFN-α induced thyroiditis and anemia during the course of treatment.

The significance of an isolated elevated TSH level in a depressed patient: a clinical commentary

OBJECTIVE

To discuss the approach to the isolated finding of an elevated thyrotropin (TSH) level on routine biochemical screening of a depressed patient.

METHOD

A focused literature review as well as discussion of published clinical guidelines and the formulation of a rational clinical approach.

RESULTS

Screening for thyroid dysfunction is part of the routine assessment of the depressed patient. It is not uncommon for such patients to have an isolated elevation of TSH levels with nor laboratory or clinical features of thyroid disease. There is often misunderstanding about how to deal with this isolated laboratory finding which can lead to unnecessary investigation and treatment.

CONCLUSIONS

A rational approach to evaluation and management of an isolated elevated TSH level is suggested.

Reversible morbidity markers in subclinical hypothyroidism

IMPORTANCE

Subclinical hypothyroidism (SCH) is a common clinical entity with a putative role in a wide range of disorders. The impact of SCH on mortality and markers of morbidity has been demonstrated, but studies have shown inconsistent results. Evidence regarding the effect of levothyroxine treatment on reversing morbidity markers is emerging, but the value of treatment is still unclear.

OBJECTIVE

The objectives of this review were to assess recent, high-quality studies evaluating the role of SCH in cardiovascular health, cognition, mood, pregnancy, anemia, and renal disease; to examine the effects of levothyroxine on reducing mortality or reversing markers of morbidity in these conditions; and to consider how new research insights may help guide clinical practice.

EVIDENCE REVIEW

A PubMed search was conducted (using 'subclinical hypothyroidism' [Title/Abstract] AND morbidity [MeSH Subheading] as search criteria) and was restricted to human studies published in the English language between 1990 and 2013. Subsequent searches of retrieved articles yielded further studies, which were included based on quality. Emphasis was given to large observational studies, well-conducted meta-analyses, and randomized controlled trials.

FINDINGS

The difficulty of diagnosing SCH, particularly in the elderly, may underlie many of the conflicting results seen in the literature. Increased understanding of the at-risk patient population will result in better selection of study subjects and, likely, unequivocal results. Regardless of the current confusion, emerging evidence suggests that certain markers of morbidity are reversed by levothyroxine therapy across the disorders examined here.

CONCLUSION AND RELEVANCE

Future large, well-controlled studies will not only clarify the role of SCH but also help identify patients for whom levothyroxine treatment will provide the most benefit.

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.

Impact of thyroid status and age on comprehensive geriatric assessment

This study aimed to evaluate the prevalence of thyroid dysfunction in elderly subjects attending an outpatient clinic at a tertiary hospital and to assess whether subclinical hypothyroidism (SCH) or aging affected activities of daily living (ADLs), instrumental activities of daily living (IADLs), cognitive status, or depressive symptoms. This crosssectional study included 411 patients recruited in the outpatient geriatric setting. 48 subjects reported levothyroxine use and were evaluated separately. After excluding subjects with diseases or drugs which could influence thyroid status, the 284 subjects remaining were classified as having euthyroidism (n = 235, 82.8 %), subclinical hypothyroidism (n = 43, 15.1 %), subclinical hyperthyroidism (n = 4, 1.4 %), or overt hyperthyroidism (n = 2, 0.7 %). ADLs and IADLs were assessed using the Katz Index (ranging from 0 [independence] to 6 [dependence in all activities]) and Health Assessment Questionnaire (ranging from 0 to 3 [severely disabled]), respectively. Cognition was assessed using the mini mental state depressive symptoms that were assessed using the Geriatric depression scale or cornell scale for depression in dementia. SCH did not reduce performance in ADLs or IADLs in elderly subjects as a whole, but was an independent protective factor against dependence in ADLs (OR = 0.196 [0.045-0.853]; p = 0.003) and IADLs (OR = 0.060 [0.010-0.361]; p = 0.002) in subjects aged ≥85 years. Very old subjects with SCH showed better performance in ADLs than did those with euthyroidism (Katz Index: 0.9 ± 1.6 [median: 0.5] vs. 1.7 ± 1.7 [1.0], p = 0.024; HAQ: 1.2 ± 0.8 [0.9] vs. 1.8 ± 1.0 [1.9], p = 0.015). This putative protective effect of SCH was not found in subjects aged <85 years. The number of falls, number of medications used, depressive symptoms, and cognitive impairment did not differ among thyroid status groups, regardless of age. In conclusion, SCH does not have impact functional performance in the elderly population as a whole, but was associated with better functional status in subjects aged ≥85 years.

Neurologic complications of nondiabetic endocrine disorders

PURPOSE OF REVIEW

This article provides an overview of the neurologic complications found in the various endocrine disorders affecting adult patients. Specifically, disorders in pituitary hormones (prolactin, growth hormone, vasopressin, and oxytocin), thyroid hormones, adrenal hormones (glucocorticoids), and sex hormones (estrogen and testosterone) will be covered, with an emphasis on identifying the signs and symptoms in addition to diagnosing and managing these disorders.

RECENT FINDINGS

Hyperthyroidism in the young was found to increase the risk for ischemic stroke in a recent prospective case-cohort study. The cognitive effects of hormonal therapy in postmenopausal women remain controversial, but a recent study found no benefit or risk in cognitive function when treating younger (50 to 55 years of age) postmenopausal women with hormonal therapy.

SUMMARY

Endocrine disorders can cause various neurologic complications, from insidious myopathy to acute encephalopathy. Diagnosing the endocrine disorder as the cause of the neurologic impairment is essential, as treating the underlying hormonal dysfunction will often rapidly reverse the neurologic symptoms. Ongoing research is needed to further clarify the role of hormonal dysfunction in neurologic disorders.

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.

Depression-like behavior in subclinical hypothyroidism rat induced by hemi-thyroid electrocauterization

The purpose of this study was to investigate the depression-like behavior performances of subclinical hypothyroidism (SCH) rat. SCH rat model was induced by hemi-thyroid electrocauterization, and the behavior performances were measured by sucrose preference test, force swimming test (FST), and tail suspension test (TST). SCH rat model was established successfully by hemi-thyroid electrocauterization. In the behavior tasks, SCH rats displayed depression-like behavior were indicated as a significant elevation of immobility time in both the TST and FST, though the sucrose preference was not significantly decreased. The index of left adrenal cortex in both SCH and clinical hypothyroidism (CH) group significantly increased, and many large lipid vacuoles were observed in the zona fasciculata cells. The serum corticosterone concentration and hypothalamic corticotropin-releasing hormone mRNA expression 2 h after behavior test was markedly up-regulated in CH rats, but not SCH rats, indicated that SCH induced a less impairment of HPA axis than CH did. The important finding of this study was that the concentration of hippocampal T3 was lower in SCH group than that of the sham group. Furthermore, the results of Pearson correlation test showed that the immobility behaviors in TST and FST were both negatively correlated with hippocampal T3 concentration. Taking together, our results indicated that SCH could result in depression-like behavior, accompanied with subtle hyperactivity of HPA axis. The reduced hippocampal T3 prior to the reduction of thyroid hormone in serum might be taken as an early sign of hippocampus impairment in the progression from SCH to CH.

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.

2013 ETA Guideline: Management of Subclinical Hypothyroidism

Subclinical hypothyroidism (SCH) should be considered in two categories according to the elevation in serum thyroid-stimulating hormone (TSH) level: mildly increased TSH levels (4.0-10.0 mU/l) and more severely increased TSH value (>10 mU/l). An initially raised serum TSH, with FT4 within reference range, should be investigated with a repeat measurement of both serum TSH and FT4, along with thyroid peroxidase antibodies, preferably after a 2- to 3-month interval. Even in the absence of symptoms, replacement therapy with L-thyroxine is recommended for younger patients (<65-70 years) with serum TSH >10 mU/l. In younger SCH patients (serum TSH <10 mU/l) with symptoms suggestive of hypothyroidism, a trial of L-thyroxine replacement therapy should be considered. For such patients who have been started on L-thyroxine for symptoms attributed to SCH, response to treatment should be reviewed 3 or 4 months after a serum TSH within reference range is reached. If there is no improvement in symptoms, L-thyroxine therapy should generally be stopped. Age-specific local reference ranges for serum TSH should be considered in order to establish a diagnosis of SCH in older people. The oldest old subjects (>80-85 years) with elevated serum TSH ≤10 mU/l should be carefully followed with a wait-and-see strategy, generally avoiding hormonal treatment. If the decision is to treat SCH, then oral L-thyroxine, administered daily, is the treatment of choice. The serum TSH should be re-checked 2 months after starting L-thyroxine therapy, and dosage adjustments made accordingly. The aim for most adults should be to reach a stable serum TSH in the lower half of the reference range (0.4-2.5 mU/l). Once patients with SCH are commenced on L-thyroxine treatment, then serum TSH should be monitored at least annually thereafter.

Neuropsychiatric manifestations of thyroid disease

The interface between thyroid hormone action and neuropsychiatric function is intricate, and several mechanisms of thyroid hormone uptake into brain tissues, hormone activation, and influences on neurotransmitter generation have been identified. Symptoms of hypothyroidism are nonspecific, whereas those attributed to thyrotoxicosis may be more characteristic. Neuropsychiatric manifestations triggered by thyroid dysfunction likely respond well to reestablishment of the euthyroid state, although some patients have persistent complaints. The addition of LT3 to ongoing LT4 replacement has yet to be definitively shown to be advantageous. Treatment of euthyroid depression with LT3 in addition to antidepressant therapy lacks convincing evidence of superior outcomes.