I had hypo I think since my pregnancy. At 34. I wasn't diagnosed until a decade later, because my blood work was confusing, and only a radio uptake scan showed a damaged gland.

My internist thinks I had it longer however.
I don't think treatment for thyroid is perfect...it is close, but the human body is very complicated and highly balanced and humans just cannot duplicate the thyroid actions well.

At least I don't have the autoantibodies, and my last test was negative for them (in Dec.). Some people do swing up and down and that may signal Hashimoto's. But then I am not an expert on this-- only just another cryptic case that eluded detection!

By the time I got Synthroid, my feet were pretty numb and my hands were moderate. It took a year, but my feet did wake up, only not 100%. I'd say I have about 10% residual numbness in the tips of 2 toes on each foot (next to the big toe). I also have arthritis and broken sesamoid bones, and the terrible scar, which now throbs some days. That took 50 yrs to manifest! It is like a blast from the past, that scar, now! This scar is S shaped, and covers 80% of the instep. It had a zillion small stitches from the plastic surgeon who did not graft skin to cover the hole left from removing the tumor, but pulled the skin over to cover instead. Said it would heal better. It was a LONG recovery I remember! I was just a 12 yr old then with lots of restrictions etc. It is a difficult place to fix. The magnesium lotion stops it from throbbing which seems to happen when I go to bed at night. During the day it stings some depending on the shoe I might have on. Last 3 days that foot has been swelling again. sigh.