Thyroid function and cognition in the euthyroid elderly: A case–control study embedded in Quebec longitudinal study – NuAge

Castellano, Christian‐Alexandre; Laurin, Danielle; Langlois, Marie‐France; Fortier, Mélanie; Tessier, Daniel; Gaudreau, Pierrette; Ferland, Guylaine; Payette, Hélène; Lorrain, Dominique; Cunnane, Stephen C.

doi:10.1016/j.psyneuen.2013.02.013

Cited by 17 publications

(12 citation statements)

References 28 publications

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“…After carefully scanning the titles and abstracts, 39 articles that were potentially eligible for inclusion were retrieved. After reading the full texts, 28 articles were excluded for the following reasons: nine studies were not cohort or case-control studies181920212223242526; 13 lacked usable data13141727282930313233343536; four had different study purposes37383940; one did not perform FT4 and TSH measurements41; and one was a replicate study with a shorter follow-up42 than that by de Jong et al 10 (Fig. 1).…”

Section: Resultsmentioning

confidence: 99%

Higher FT4 or TSH below the normal range are associated with increased risk of dementia: a meta-analysis of 11 studies

Pei

Wang

et al. 2016

Sci Rep

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Observational studies of thyroid function and dementia have reported conflicting results. We reviewed cohort and case-control studies from MEDLINE, EMBASE, Web of Science and the Cochrane Library that focused on the association between serum thyroxine, thyrotropin and dementia. A total of 24,952 participants from three case-control and eight cohort studies were included. The relationships between dementia and the per standard deviation (SD) increment of free thyroxine (FT4) (random relative ratio (RR) = 1.08, 95% confidence interval (CI) 1.00–1.17) and thyroid-stimulating hormone (TSH) (fixed RR = 0.91, 95% CI 0.84–0.99) were well established. TSH levels in the low category were associated with an increased risk of dementia (fixed RR = 1.60, 95% CI 1.27–2.00). However, the positive association was confined to TSH levels below the normal range (fixed RR = 1.77, 95% CI 1.31–2.39), not those in the lower tertile of the normal range (fixed RR = 1.39, 95% CI 0.98–1.97). Additionally, dementia was not significantly associated with high TSH levels (fixed RR = 0.99, 95% CI 0.76–1.29). Furthermore, there was no positive association between dementia and the low or high categories of TSH in men. Thus, individuals with higher FT4 levels or those with TSH levels below the normal range have an increased risk of dementia.

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Section: Resultsmentioning

confidence: 99%

Higher FT4 or TSH below the normal range are associated with increased risk of dementia: a meta-analysis of 11 studies

Pei

Wang

et al. 2016

Sci Rep

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“…Normal aging is associated with changes in the production of thyroid hormones and their metabolism[21]. Secretion of thyroxine and triiodothyronine is reduced in healthy aged individuals, and an age-dependent decline in circulating total and free triiodothyronine concentrations occur because of reduced peripheral conversion from thyroxine hence decreased secretion[21]. However, serum concentrations of total and free thyroxine remain relatively unchanged in these individuals because thyroxine degradation is reduced[2223].…”

Section: Discussionmentioning

confidence: 99%

The synthetic thyroid hormone, levothyroxine, protects cholinergic neurons in the hippocampus of naturally aged mice

Zhou

2014

Neural Regen Res

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The thyroid hormones, triiodothyronine and thyroxine, play important roles in cognitive function during the mammalian lifespan. However, thyroid hormones have not yet been used as a therapeutic agent for normal age-related cognitive deficits. In this study, CD-1 mice (aged 24 months) were intraperitoneally injected with levothyroxine (L-T4; 1.6 μg/kg per day) for 3 consecutive months. Our findings revealed a significant improvement in hippocampal cytoskeletal rearrangement of actin and an increase in serum hormone levels of L-T4-treated aged mice. Furthermore, the survival rate of these mice was dramatically increased from 60% to 93.3%. The Morris water maze task indicated that L-T4 restored impaired spatial memory in aged mice. Furthermore, level of choline acetyltransferase, acetylcholine, and superoxide dismutase were increased in these mice, thus suggesting that a possible mechanism by which L-T4 reversed cognitive impairment was caused by increased activity of these markers. Overall, supplement of low-dosage L-T4 may be a potential therapeutic strategy for normal age-related cognitive deficits.

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“…TSH is considered the most important indicator for the evaluation of thyroid function [ 6 ]. FT3 and FT4 are the active biological state in plasma, and therefore, FT3 and FT4 are considered to be sensitive and meaningful indicators for the diagnosis of thyroid disease.…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, T4 is more reliable than T3 in assessing thyroid function in patients with hypothyroidism. From Castellano's study, the analyses of five serum indicators, including TT4, TT3, FT4, FT3, and TSH, in patients with hypothyroidism showed that the correlation between TT4, FT4, and TSH was closer than the correlation of TT3, FT3, and TSH with TSH which was the most important indicator in the diagnosis of hypothyroidism [ 6 ]. Thus, it can be interpreted that T4 is more suitable than T3 in assessing thyroid function in hypothyroidism patients.…”

Section: Discussionmentioning

confidence: 99%

“…In a survey from 110 countries (mostly in developing countries), hyperthyroidism and hypothyroidism were considered responsible for the morbidity at large [ 4 ]. TSH regulates the synthesis and secretion of the thyroid hormone through the hypothalamic-pituitary-thyroid axis [ 5 ] and is considered the primary indicator to assess thyroid function [ 6 ]. Currently, thyrotropin (TSH), free thyroxine (FT4), or FT4 combined with total triiodothyronine (TT3) is recommended for use as indicators in laboratory testing to assess thyroid function clinically (e.g., in the guidelines of the American Thyroid Association (ATA)) [ 7 , 8 ].…”

Section: Introductionmentioning

confidence: 99%

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Clinical Evaluation of Various Thyroid Hormones on Thyroid Function

Yuan

Liu

et al. 2014

International Journal of Endocrinology

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To clarify the clinical value of serums total triiodothyronine (TT3), total thyroxine (TT4), free triiodothyronine (FT3), and free thyroxine (FT4) and provide a more eligible and economic strategy to assess thyroid function. A total of 2,673 participants (500 patients with hyperthyroidism, 500 patients with hypothyroidism, and 1,673 healthy people) were involved in our study. Serums TT3, TT4, FT3, and FT4 and thyrotropin (TSH) were measured with VIDAS fluorescent enzyme immunoassay. The Pearson correlation between TT3, TT4, FT3, and FT4 and TSH was determined to identify the most important indicator for thyroid function besides TSH. The correlation of TT4, and FT4 with TSH was statistically significant in healthy individuals (P < 0.01), and the R-values were −0.065 and −0.152, respectively. The correlation of TT4, FT4, TT3, and FT3 with TSH was statistically significant in patients with hyperthyroidism, and the R-values were −0.241, −0.225, −0.195, and −0.176, respectively. The correlation of TT4, FT4, TT3, and FT3 with TSH was statistically significant in patients with hypothyroidism, and the R-values were −0.322, −0.262, −0.179, and −0.136, respectively. In our opinion, TSH and FT4 are the most valuable indicators in assessing thyroid function in a healthy population, and TSH and TT4 are the most meaningful in hyperthyroidism and hypothyroidism.

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Thyroid function and cognition in the euthyroid elderly: A case–control study embedded in Quebec longitudinal study – NuAge

Cited by 17 publications

References 28 publications

Higher FT4 or TSH below the normal range are associated with increased risk of dementia: a meta-analysis of 11 studies

Higher FT4 or TSH below the normal range are associated with increased risk of dementia: a meta-analysis of 11 studies

The synthetic thyroid hormone, levothyroxine, protects cholinergic neurons in the hippocampus of naturally aged mice

Clinical Evaluation of Various Thyroid Hormones on Thyroid Function

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