Serum Thyrotropin Levels Across Older Age Groups in Geriatric Outpatients Without Documented or Clinically Evident Thyroid Disease: A Retrospective Cross-Sectional Study

Background/Objectives: Reported age patterns in serum thyroid-stimulating hormone (TSH) vary across populations and assays. We examined age and sex associations with TSH levels in clinically selected geriatric outpatients in Ankara, Türkiye.

Methods

This retrospective cross-sectional study analyzed records from 1 October to 31 December 2022. After clinical, medication, and laboratory exclusions, 206 participants aged ≥65 years remained. Linear regression of log-transformed TSH included age per five years and sex, with HC3 robust standard errors. Sensitivity models added comorbidities and medication count and applied the institution-specific TSH and fT4 reference intervals. Exploratory quantile regression used bootstrap confidence intervals (CIs) and formal comparisons of percentile-specific coefficients.