One more for those who know more

Am I understanding this correctly. Hyperthyroidism a rare disorder perhaps 1-3% of the population and the scourge of my life the last 40 years as a caregiver.

So the thyroid secretes an A antigen in a human with a blood type for example O-?

How the heck did the wrong thyroid get installed in the wrong body?

It does not make sense?