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Objective: As thyroid hormone metabolism slows with advancing age, treatment dosing requirements change. Guidelines recommend titration from a low starting dose for older adults with hypothyroidism while providing weight-based estimates for younger populations. However, rapid replacement may be appropriate with acute onset of overt hypothyroidism. Therefore, a weight-based recommendation specific to older adults is needed., Methods: We determined mean levothyroxine dose using actual and ideal body weight (IBW) ratios for the outcome of euthyroid on therapy relative to assay-specific and proposed age-specific ranges for independently living participants aged ≥65 years in the Baltimore Longitudinal Study of Aging. We examined risk factors to identify those at highest risk of overtreatment using regression analyses adjusted for potential covariables and clustering to account for multiple visits per individual., Results: One hundred eighty-five participants aged ≥65 years were on levothyroxine at 645 eligible visits. At euthyroid visits, participants were on an average dose of 1.09 μg/kg (1.35 μg/kg IBW), with 84% of euthyroid individuals on a dose of <1.6 μg/kg. Average euthyroid dose did not differ by sex using either actual body weight (ABW) or IBW. For obese individuals, mean euthyroid dose was lower if calculated using ABW (0.9 μg/kg vs 1.14 μg/kg; P < .01) but similar if calculated using IBW (1.42 vs 1.32 μg/kg IBW; P = .41) compared with those with a body mass index of <30., Conclusion: Thyroid hormone dose per body weight estimates for replacement in older adults (1.09 μg/kg ABW or 1.35 μg/kg IBW) are one-third lower than current weight-based dose recommendations for younger populations., Competing Interests: Disclosure The authors have no multiplicity of interest to disclose., (Copyright © 2023 AACE. All rights reserved.)

Background: Although elevated thyrotropin (TSH) is common in older adults, controversy exists over what degree of elevation should be treated with thyroid hormone supplements. Isolated, elevated TSH in this population can be consistent with aging-related adaptations rather than indicative of primary thyroid disease, raising the possibility that thyroid hormone replacement may be harmful., Objectives: Determine the association between all-cause mortality and levothyroxine use among older adults., Design: Longitudinal observational study., Setting: Baltimore Longitudinal Study of Aging., Participants: One thousand two hundred and fifty eight community dwelling adult participants aged 65+ with an average of 9 years of follow up., Measurements: Thyroid and pituitary hormone levels and thyroid hormone supplementation were determined at each visit. Incident rate ratios (IRR) for all-cause mortality were calculated using time-dependent Poisson regression models to accommodate the varying start times. To isolate the effects of hormone replacement from its effects on TSH, the association between treatment and all-cause mortality was analyzed in participants with stable thyroid function status throughout follow-up (N = 638)., Results: Thyroid hormone supplementation was not associated with a significant increase all-cause mortality in the subsequent year in the fully adjusted model (IRR = 1.40, 95% confidence interval (CI) = 0.93-2.12). In a stratified analysis of euthyroid participants, thyroid hormone use was associated with significantly greater mortality, with an adjusted IRR = 1.81 (95% CI = 1.10-2.98)., Conclusion: The increased mortality associated with thyroid hormone use among the subclass of euthyroid community dwelling older adults is consistent with a model in which TSH elevation can result from a variety of underlying pathophysiologic processes, not all of which should be treated with thyroid hormone supplementation. Clinicians should consider overall clinical status when interpreting an isolated elevated TSH in older adults., (© 2021 The American Geriatrics Society.)

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.