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

ABSTRACT: 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.

SUBMITTER: Wu Y

PROVIDER: S-EPMC4997309 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature

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

Wu Yue Y Pei Yuqing Y Wang Fei F Xu Danfei D Cui Wei W

Scientific reports 20160825

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 rati ...[more]

PMID: 27558885

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Project description:Background: Serum thyroid-stimulating hormone (TSH) and free thyroxine (FT4) change dynamically during pregnancy. Differences in geographic regions, populations, and manufacturer's methodologies can affect the reference intervals for thyroid function tests. The 2017 guidelines of the American Thyroid Association (ATA) recommended 4.0 mU/L as the cut-off point for the upper limit of serum TSH in early pregnancy. A systematic review is called for to establish practical, gestational-specific TSH and FT4 reference intervals for pregnant Chinese women and to explore whether the criteria are suitable for China. Methods: English and Chinese articles published from inception to Aug 2017 were searched in the PubMed, EMBASE, and SCIE English-language databases and the CNKI, WanFang, and CQVIP Chinese databases. The relative descent or ascent rates of serum TSH and FT4 were calculated, after which Comprehensive Meta-Analysis V2.0 software was used to analyze the data. Results: Eleven studies (6 in English and 5 in Chinese), five kits and 11,629 Chinese women from nine cities were considered in this meta-analysis. Compared with the reference ranges provided by manufacturers, serum TSH decreased in the first trimester, with the upper limit declining by 21.7% (5.0-36.6%), to a value close to 4.0 mU/L, and the lower limit declining by 85.7% (73.5-97.1%). It continued decreasing in the second trimester, with the upper limit declining by 24.0% (6.4-40.9%) and the lower limit declining by 40.7% (9.0-85.7%). For FT4, the upper limit fluctuated slightly, and the lower limit increased by 6.8% (1.0-14.6%) in the first trimester. Serum FT4 dropped gradually, with the upper limit declining by 21.8% (2.5-31.8%) and the lower limit declining by 12.7% (2.6-19.6%) in the second trimester. During the third trimester, the upper limit decreased by 25.1% (12.7-35.0%), while the lower limit decreased by 20.9% (14.8-27.3%). Conclusions: Various regions, kits and test methods affect the gestational TSH and FT4 levels. The non-pregnant serum TSH upper limit minus 22% is very close to 4.0 mU/L, which can be used as a sub-optimal approach to represent the cut-off value for pregnant Chinese women in the first trimester.

Project description:Evidence regarding thyroid-stimulating hormone (TSH) levels within the normal range and mortality in adults with diabetes is scarce. This study aimed to identify the association between TSH levels and cardiovascular disease (CVD) and all-cause mortality among euthyroid patients with diabetes. This prospective cohort study included 1830 adults with diabetes from the Third National Health and Nutrition Examination Survey III. Mortality outcomes were ascertained by linkage to National Death Index records through December 31, 2019. Participants were categorized by tertiles of TSH levels (low-normal, 0.39-1.30 mIU/L; medium-normal, 1.30-2.09 mIU/L; high-normal, 2.09-4.60 mIU/L). Multivariable Cox proportional hazards models were used to explore the association between TSH levels within the normal range and overall and CVD mortality. Furthermore, restricted cubic spline analyses were used to determine the nonlinear relationship between TSH levels and mortality. During a median follow-up of 17.1 years, 1324 all-cause deaths occurred, including 525 deaths from CVD. After multivariate adjustment, a U-shaped relationship was observed between TSH levels in euthyroid status and all-cause or CVD mortality among patients with diabetes (both P < 0.05 for nonlinearity). Compared with participants with medium-normal TSH levels, those with high-normal TSH levels had a significantly higher risk of all-cause (hazard ratio, 1.31; 95% confidence interval, 1.07-1.61) and CVD (1.52; 1.08-2.12) mortality. Similarly, low-normal TSH levels also increased all-cause (1.39; 1.12-1.73) and CVD (1.69; 1.17-2.44) mortality risk. In stratum-specific analyses, we found that high-normal TSH levels were associated with higher mortality risk in younger (< 60 years) patients with diabetes but not in older (≥ 60 years) participants. Low- and high-normal serum TSH levels were associated with increased all-cause and CVD mortality in euthyroid adults with diabetes. Further studies are needed to confirm the present observation in a wider population.

Project description:BackgroundAlteration in thyroid activity is a well-known cause of symptoms mimicking psychiatric disorders. There are reports on altered levels of thyroid hormones in patients with certain psychiatric disorders compared to healthy controls; still, the magnitude and importance of the phenomenon is not known. We wanted to explore the level of thyroid hormones in different diagnostic groups in an acute-psychiatric population. We also wanted to follow any change during their stay.MethodsPatients aged 18 years and older admitted to a closed, psychiatric inpatient ward were eligible if giving informed consent. For 539 patients representing all main psychiatric diagnostic groups and with equal gender distribution, data for FT4 were available for 539 patients, and data for TSH were available from 538 patients at admittance. For 239 patients, data for FT4 were available at both admittance and discharge, and the corresponding number for TSH was 236 patients.ResultsA significantly higher share of patients had higher levels of FT4 and TSH at admittance than expected for healthy individuals. No significant effect of gender or most diagnostic groups was seen. For female patients with substance-use disorder (SUD), the level of TSH was significantly lower than that for all other diagnostic groups. No other difference in the levels of FT4 and TSH was seen between the main diagnostic groups, and the effect in SUD was not seen in males. For the population with available markers at both admittance and discharge, in total, there was a significant reduction of FT4 from admittance to discharge, not followed by any change in TSH.ConclusionsIn acutely admitted psychiatric patients there seems to be an increased FT4 and TSH. FT4 is normalized during the inpatient stay independently of TSH. This indicates somatic effects of psychiatric stress that may be of clinical importance and the phenomenon should be further explored. Mainly different diagnostic groups did not differ in level of FT4 and TSH. Thus future studies on thyroid activity in psychiatric patients should focus on function and level of stress and suffering rather than diagnostic groups.

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

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

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