SLC5A5 and goiter: Experimental validation included: (1) establishing a propylthiouracil (PTU)-induced goiter rat model with 16S rRNA sequencing of fecal samples, (2) targeted SCFAs quantification, (3) thyroid/serum iodine measurement, (4) thyroid hormone assays, and (5) sodium-iodide symporter (NIS) protein expression analysis.