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The article discusses the results of the health, aging and body composition study on the link between thyroid hormone use and the diagnosis of dementia. Topics mentioned include the distribution of thyroid stimulating hormone (TSH) by thyroid hormone use and dementia status, the risk of isolated TSH elevation for iatrogenic thyrotoxicosis resulting to accelerating cognitive decline, and the association of thyroid hormone supplementation with increased risk of both over and under-treatment.

Background: Emerging evidence suggests that mildly down-regulated thyroid function in older persons may protect and/or reflect maintained health.Methods: Using observational data collected between January 2006 and March 2014 on a volunteer sample of 602 men and women aged 68-97 years with normal thyroid function participating in the Baltimore Longitudinal Study of Aging, this study examines the concurrent relationship between reported walking ability, usual and rapid gait speed, endurance walk performance, fatigability, and reported energy level with respect to free thyroxine (FT4) within the normal range (0.76-1.50ng/dL) as a continuous variable and categorized as low (lower quartile), medium (interquartile), or high (upper quartile).Results: Adjusting for sex, age, race, height, weight, exercise and smoking, reported walking ability, usual and rapid gait speed, 400-m time, fatigability, and reported energy level were less favorable with increasing FT4 (p = .013 to <.001). In sex-strata, similar associations were observed except for walking ability in men and energy level in women. Categorical analyses revealed that persons with low FT4 exhibited better functional mobility, fitness, and reported energy than persons with intermediate or high levels (p < .05 for all). Persons with high-normal versus medium FT4 had slower usual and rapid gait speed (p < .05) only.Conclusion: Older adults with low-normal FT4 exhibit better mobility, fitness, and fatigue profiles. Mildly down-regulated thyroid function appears to align with better function in old age and may serve as a biomarker of healthy longevity. [ABSTRACT FROM AUTHOR]

Background: Both endogenous and exogenous thyrotoxicosis has been associated with atrial fibrillation and low bone mineral density. Therefore, this study investigated the risk factors associated with prevalent and incident thyrotoxicosis and the initiation of thyroid hormone therapy in a healthy, aging cohort. Methods: A total of 1450 ambulatory community volunteer participants in the Baltimore Longitudinal Study of Aging examined at the NIA Clinical Research Unit in Baltimore, MD, have undergone longitudinal monitoring of serum thyrotropin (TSH) and thyroid hormone (free thyroxine and free triiodothryonine) levels as well as medication use every one to four years, depending on age, between 2003 and 2014. Results: The prevalence of low TSH was 9.6% for participants on thyroid hormone and 0.8% for nontreated individuals ( p < 0.001). New cases occurred at a rate of 17.7/1000 person-years of exposure to thyroid hormone therapy [CI 9-32/1000] and 1.5/1000 person-years in the unexposed population [CI 0.7-2.9/1000]. Women were more likely to be treated and more often overtreated than men were. The adjusted hazard ratio (HR) for thyrotoxicosis between treated and untreated women was 27.5 ([CI 7.2-105.4]; p < 0.001) and 3.8 for men ([CI 1.2-6.3]; p < 0.01). White race/ethnicity and older age were risk factors for thyroid hormone therapy but not overtreatment. Body mass index was not associated with starting therapy (HR = 1.0). Thyroid hormone initiation was highest among women older than 80 years of age (3/100 person-years). For one-third of treated participants with follow-up data, overtreatment persisted at least two years. Conclusions: Iatrogenic thyrotoxicosis accounts for approximately half of both prevalent and incident low TSH events in this community-based cohort, with the highest rates among older women, who are vulnerable to atrial fibrillation and osteoporosis. Physicians should be particularly cautious in treating subclinical hypothyroidism in elderly women in light of recent studies demonstrating no increased risk of cardiovascular morbidity or death for individuals with elevated TSH levels <10 mIU/L. [ABSTRACT FROM AUTHOR]