That’s the red-herring, T4 (free specifically) is active and the body has receptors for it. So much focus is put on ft3 and rt3, but missing the point of having higher ft4 being beneficial for your health.
T4 is very important in males, which you will see in the article. It mentions that the ft3 and various other parameters are all identical with the exception of ft4, which is causing the ED/libido issues because it’s lower. You will also see that prolactin (and estrogen) is elevated in lower ft4 patients. Once this is fixed, erections return to normal and I can only assume libido does as well.
In another thread, I commented about the same thing and me and @dextermorgan exchanged thyroid labs. He has a high libido (as stated in his previous posts) and no ED issues. He is on a high dosage of TRT, but seeing good results. Our labs match up pretty much identically with the exception of Free T4, which (when converted) on his is around 15.3 which is the level needed as per stated in all journels/articles for normal thyroid function in people. When I was fully functioning, my level was around 15.9.
When I converted mine it was around 8-9, which is wayyyy too low and would be considered acute subclinical hypothyroidism since my Free T3 is in range.
You can see the thread here: Varicocele Influence on Testosterone - #38 by dextermorgan