Abstract
To assess studies that evaluate the relation between serum thyrotropin concentration, very old subjects, and their events. We searched the PubMed, SciELO, and LILACS databases for articles published between 2004 and 2012. Our search was restricted to studies involving humans aged 65 years or older, and written in English, Spanish, or Portuguese. Studies that evaluated the association between elevated serum thyrotropin concentration among elderly subjects with subclinical hypothyroidism were chosen since at least in part they included a subpopulation of individuals aged 80 years and above. Thirteen studies were selected. No significant increase in risk of cardiovascular events, coronary heart disease, or total mortality was observed. Elevated thyrotropin concentration was associated with longevity. More randomized controlled trials are required to better define the potential benefits of elevated thyrotropin concentration in this oldest old population, hormone replacement, and longevity.
Highlights
Subclinical hypothyroidism is a laboratory diagnosis(1) defined by an abnormally high serum thyrotropin (TSH) level associated with a normal plasma concentration of free thyroxin.(2-4) It is common among elderly individuals and its prevalence increases with age, affecting 6% of population between 70 and years and 10% of individuals above years of age.(5,6) The prevalence of subclinical hypothyroidism is lower in blacks compared with whites, in women over the age of 80 years, and in populations with iodine deficiency.(1)
Studies evaluating the association between elevated serum TSH levels among elderly subjects with subclinical hypothyroidism were included, since at least in part, they included a subpopulation of individuals aged 80 years and more
One was a longitudinal epidemiological study(9) involving six centers in England and Wales evaluating the association between cognitive decline, assessed by the Mini-Mental State Examination (MMSE), and high TSH levels in
Summary
Subclinical hypothyroidism is a laboratory diagnosis(1) defined by an abnormally high serum thyrotropin (TSH) level associated with a normal plasma concentration of free thyroxin (fT4).(2-4) It is common among elderly individuals and its prevalence increases with age, affecting 6% of population between 70 and years and 10% of individuals above years of age.(5,6) The prevalence of subclinical hypothyroidism is lower in blacks compared with whites, in women over the age of 80 years, and in populations with iodine deficiency.(1)Subclinical thyroid dysfunction has been associated with several negative clinical outcomes such as hypercholesterolemia, atherosclerosis,(7) coronary heart disease events and mortality,(2,7) cognitive impairment,(2,8,9) depression,(10) disability,(2) lower physical function,(11) and risk of progression to overt hypothyroidism.(12)Serum TSH concentration increases slightly in very old healthy individuals,(13) regardless of the presence of antithyroid antibodies(5,14) and along with an agedependent decline in serum free and total triiodothyronine (T3), suggesting that some very elderly individuals118 Duarte GC, Cendoroglo MS, Araújo LM, Almada Filho CM may have an altered set point of the hypothalamicpituitary-thyroid axis.(4) Despite a likely increase in serum reverse triiodothyronine (rT3) with age,(11) free and total serum thyroxin (T4) concentrations remain unchanged, complicating the interpretation of these measurements since concomitant chronic illnesses and use of medications are often present in this population. It is possible that the decrease in thyroid function and metabolic rate(11) may be adaptive mechanisms to prevent catabolism and reduce damage to DNA by reactive oxygen species.(13) reports have demonstrated that centenarians(14) and their offspring have higher serum TSH levels, characterizing a heritable phenotype.(15-17). Despite this evidence, the hypothesis that some degree of physiological decrease in thyroid activity at a tissue level may favor effects in oldest old subjects remains uncertain
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