@missey Hi, please provide a link to the study you mention showing no need for Synthroid after 65.
Up until three years ago I had never taken a thyroid medication and the numbers like the TSH did not indicate a great need for it.
I started taking Armor Thyroid when I was 72 and it was a game changer. More energy and vitality and it coincided at least with a lessoning of 40 years of food and chemical sensitivities.
The status quo in medicine is to treat the thyroid by the numbers. But before that low thyroid was treated by the symptoms. I'm combining the two.
My favorite information source on Thyroid is Alan Gaby MD. Here's a couple of older pieces by him. There are more recent updates and comments in the Townsend Letter where he had a column, which largely express the same opinion. That you've got to be informed by the symptom picture and that for many patients (but not all) thyroid meds with T3 and T4 give better symptom results than Synthroid.
https://altmedrev.com/wp-content/uploads/2019/02/v9-2-157.pdf
https://townsendletter.com/editorial-06-22-gaby-practice-guidelines-for-the-treatment-of-hypothyroidism/