Second, despite a 5-fold elevation of TSH (Figure 4A), there was no evidence of thyroid gland growth after GRP170 deletion (Figure 3B and Supplemental Figure 1B) and no increased expression of any TSH-dependent thyroid genes (Figure 5C) that are known to be upregulated in primary hypothyroidism (Supplemental Figure 3). Here, HYOU1 is linked to hypothyroidism.