Serum thyroxine level and cognitive decline in euthyroid older women

Abstract

In older women, low T(4) levels, within the normal range, were associated with a greater risk of cognitive decline over a 3-year period. Thyroid hormone levels may contribute to cognitive impairment in physically impaired women.

Longitudinal evidence of the impact of normal thyroid stimulating hormone variations on cognitive functioning in very old age

“…The prospective analyses of baseline TSH and thyroxine regressed on cognitive change were included in order to replicate the study by Volpato et al (2002). Similar to that study, we found that baseline TSH did not predict future decline of cognitive performance.…”

“…Wahlin et al (1998) found cross-sectional associations between TSH but not thyroxine and episodic memory. Volpato et al (2002) and van Boxtel et al (2004) failed to find any cross-sectional associations involving thyroxine and TSH, respectively, but the Volpato et al study found that baseline thyroxine levels predicted future cognitive decline, particularly on tasks involving episodic memory components. Van Boxtel and colleagues (2004) argued that one explanation for the lack of TSH-related effects in their study, was that their sample was younger than that examined by Wahlin et al (1998).…”

“…Volpato et al (2002), published data on physically impaired women, aged 65 years and older, and with normal thyroid gland function at baseline, showing that low baseline thyroxine but not TSH within normal ranges predicted cognitive decline across three years, as assessed by the Mini-Mental State Examination Scale (MMSE : Folstein et al, 1975). No cross-sectional associations were detected in this study.…”

Thyroid hormones and cognitive functioning in healthy, euthyroid women: A correlational study

“…The few studies that had investigated the relationship between normal levels of THs and cognitive performance in healthy individuals found inconsistent results (Wahlin et al, 1998;Prinz et al, 1999;Volpato et al, 2002;Gussekloo et al, 2004). For example, in older, euthyroid women lower total serum T4 (TT4) levels were associated with a greater risk of cognitive decline over a 3-year period (Volpato et al, 2002).…”

“…For example, Wahlin et al (1998) found a significant positive association between TSH, but not T4, and scores on a verbal learning and memory test in individuals whose average age was 83 years. In physically impaired, but cognitively healthy 65 year old euthyroid women, lower but normal levels of total T4 were associated with a greater risk of cognitive decline over a three year period (Volpato et al, 2002). In contrast, Prinz et al (1999) found a positive correlation between total T4 levels and performance of 72-year old men on several cognitive tests, suggesting that middle to high normal levels of THs might be optimal for maintaining cognitive functions.…”