Influences of thyroid stimulating hormone on cognitive functioning in very old age.
ABSTRACT This study investigated the relationship of thyroxine (T4) and thyroid stimulating hormone (TSH) within normal ranges to cognitive performance in very old age. The participants (N = 200) were selected from a population-based study of nondemented persons aged 75 to 96 years (M = 83.9 years). Tasks assessing episodic memory, verbal fluency, visuospatial ability, short-term memory, and perceptual-motor speed were examined. Results indicated that T4 was unrelated to performance. However, TSH was positively related to episodic memory performance, and the effects were independent of the influence of age, level of education, and depressive mood symptoms. There was no reliable effect of TSH on verbal fluency, short-term memory, perceptual-motor speed, or visuospatial functioning. The influence of TSH on episodic memory was interpreted in terms of its potential effects on encoding and consolidation processes.
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ABSTRACT: Context: Several studies have reported an association between low serum TSH, or subclinical hyperthyroidism (SH), and dementia, but little emphasis has been placed on this field because not all studies have demonstrated the same association. We performed a detailed systematic review to assess the evidence available to support the association between these two conditions. Methods: We performed a systematic search through the PubMed, Embase (1996 to 2012 wk 4), Cochrane Library, and Medline (1996 to January wk 4, 2012) electronic databases using key search terms encompassing subclinical hyperthyroidism, TSH, dementia, and cognitive impairment. Results: This review examines the 23 studies that provide information about the association between SH or lower serum TSH within the reference range and cognition. Fourteen of these studies, including several well-designed and well-powered cross-sectional and longitudinal analyses, have shown a consistent finding of an association between SH with cognitive impairment or dementia. Conclusion: There is a substantial body of evidence to support the association between SH and cognitive impairment, but there is no clear mechanistic explanation for these associations. Nor is there an indication that antithyroid treatment might ameliorate dementia. Larger and more detailed prospective longitudinal or randomized controlled trials are required to inform these important questions.The Journal of clinical endocrinology and metabolism 08/2012; 97(10):3438-49. · 6.50 Impact Factor
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ABSTRACT: Thyroid hormone production, metabolism, and action change with aging. The reference ranges for serum thyrotropin and thyroid hormones are derived mainly from younger populations. Thus, the prevalence of subclinical thyroid dysfunction is increased greatly in the elderly. However, it is unclear whether mild thyroid dysfunction in the elderly is associated with adverse outcomes. In this review, we discuss current evidence-based literature on thyroid function in the elderly and whether subclinical thyroid dysfunction in the elderly should be treated.Journal of thyroid research. 01/2013; 2013:481287.
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ABSTRACT: Context:Recent evidence indicates that thyroid hormones may be closely linked to cognition among adults.Objective:We investigated associations between thyroid hormones and cognitive performance, while testing effect modification by sex, race and elevated depressive symptoms (EDS).Design:This cross-sectional study used extensive data from the HANDLS study.Setting:Baltimore City, MD, 2004-2009.Participants:U.S. adults aged 30-64y. Sample size ranged from 1,275 to 1,346.Main outcome measures:Outcomes included thirteen cognitive test scores spanning domains of learning/memory, language/verbal, attention, visuo-spatial/visuo-construction, psychomotor speed, executive function, and mental status.Results:Within reference ranges, and after Bonferroni correction, elevated free thyroxine (fT4) was associated with better performance on tests of visuo-spatial/visuo-construction ability (overall, women and African-Americans), learning/memory (women and African-Americans); whereas a higher total thyroxine (tT4) level was associated with better performance in the domain of psychomotor speed (individuals without EDS) and a higher level of both fT4 and tT4 was linked to better language/verbal test performance among men. In contrast, higher T3(%uptake) was related to better performance on tests of visuo-spatial/visuo-construction ability and psychomotor speed among Whites. When comparing above reference range to within in the overall population, and after Bonferroni correction, within reference range fT4 was linked to better performance on visuo-spatial/visuo-constrution ability and psychomotor speed, while being below the normal range thyroid stimulating hormone (TSH) level (compared to the reference range) was linked to better performance in domains of psychomotor speed and attention.Conclusions:Thyroid hormones and cognition are closely linked, differentially by sex, race and EDS status.The Journal of clinical endocrinology and metabolism 05/2013; · 6.50 Impact Factor