TPO and hematocrit: In the thyroid, this framework is particularly well developed: immune-checkpoint loci converge with thyroid-specific genes (TSHR, TG, TPO), helping explain why susceptibility clusters within families yet partitions into Graves’ disease (GD) or Hashimoto’s thyroiditis (HT) depending on additional modifiers [1,2,3,6,10,11,14,15,16].