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Do T3 and T4 Decrease with Age? Understanding Thyroid Changes

According to a 2023 review in the journal *Thyroid Research*, free triiodothyronine (FT3) levels fall with age, but thyroid-stimulating hormone (TSH) often rises. This reveals a complex reality behind the simple question: do T3 and T4 decrease with age? While T3 often shows a clear decline, the picture for T4 is more nuanced, with several factors influencing its circulating levels in older adults.