Central hypothyroidism?

I was diagnosed hypothyroidism over 10 years ago. I recently read that there are different forms of hypothyroidism, including central hypothyroidism (which stems from a problem with the pituitary gland). It’s usually is marked by low normal TSH with low FT4. This was my situation when I was diagnosed. My doctor called it subclinical hypothyroidism, but now I’m worried I may have had central (pituitary) hypothyroidism this entire time. My doctor never sent me for imaging to check for pituitary masses. Over this time, my thyroglobulin has decreased from 9.1 to 2.9. Doctor now says my thyroid is pretty much dead. Would treatment have been different if I had been diagnosed with pituitary hypothyroidism? I’m worried maybe the wrong treatment all these years has killed my thyroid.