title: Does low-normal serum TSH level adversely impact cognition in elderly adults and might methimazole therapy improve outcomes?
abstract: Serum thyroid stimulating hormone (TSH) levels increase with age. This elevation has been associated with better outcomes in very elderly subjects; however, little is known about the relationship between TSH below the lower limit of the reference range and health-related outcomes. Here, we investigated the association between cognitive impairment or depressive symptoms and low-normal serum TSH (<1.0 μIU/mL, in the reference range) in elderly subjects and whether the use of methimazole in subjects without dementia but with low-normal TSH could affect cognition or depressive symptoms. From 293 healthy adults ≥65 years old with normal TSH included in the sectional phase, only subjects without dementia were prospectively analyzed: 1) TSH ≥1.0 μIU/mL (observation; untreated); 2) TSH <1.0 μIU/mL (observation; untreated); and 3) TSH <1.0 μIU/mL (methimazole therapy). Cognition was assessed, using the Mini Mental State Examination (MMSE) and depressive symptoms (at MMSE ≥ 13) by the Geriatric Depression Scale (GDS). Age >80 years was the sole independent factor associated with dementia (OR=2.89; confidence interval [CI] 1.72-4.86; p<0.01). Prospectively, 93 completed follow-up, with 7.5% (7) receiving methimazole intervention. Untreated subjects with lower TSH showed the greatest declines in MMSE scores during follow-up that was not observed in those with serum TSH ≥1.0 μIU/mL. Lower MMSE score reductions were associated with elderly subjects receiving methimazole. There were no significant changes in depressive symptoms and GDS scores among those with serum TSH <1.0 μIU/mL. In this study, low-normal TSH was not associated with higher prevalence of dementia. However, in elderly subjects without dementia, low TSH was associated with worsening cognition.
authors.affiliation: Medicine School - Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Dhiãnah Santini de Oliveira
authors.initials: DS
authors.lastname: Chachamovitz
authors.forename: Patrícia Dos Santos
authors.initials: Pdos S
authors.lastname: Vigário
authors.forename: Silvana Oliveira E
authors.initials: SO
authors.lastname: Silva
authors.forename: Letícia B B de Mello
authors.initials: LB
authors.lastname: Teixeira
authors.forename: Michele Lopes
authors.initials: ML
authors.lastname: Fagundes
authors.forename: Mário
authors.initials: M
authors.lastname: Vaisman
authors.forename: Patrícia de F Dos S
authors.initials: Pde F
authors.lastname: Teixeira
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000097:blood*; D003071:Cognition / Q000187:drug effects; D003072:Cognition Disorders / Q000097:blood* / Q000188:drug therapy*; D003430:Cross-Sectional Studies; D003863:Depression / Q000097:blood; D005260:Female; D015577:Geriatric Assessment; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008713:Methimazole / Q000627:therapeutic use*; D010865:Pilot Projects; D012016:Reference Values; D013960:Thyroid Function Tests / Q000592:standards; D013972:Thyrotropin / Q000097:blood*
chemical_list: D008713:Methimazole; D013972:Thyrotropin