Sanger sequencing of the coding exons of SLC5A5 (RefSeq: NM_000453.3) revealed a homozygous missense mutation (c.1067C>T, p.S356F), segregating with hypothyroidism in the family (Fig. 1B), which was absent from the gnoMAD database and predicted to be pathogenic by PolyPhen-2: 0.999 (scale: 0: benign, 1.0 probably damaging), MutationTaster2, p = 0.99 (p-values close to 1 indicate a high confidence prediction) and sorting intolerant from tolerant: 0.00 (scale 0: deleterious, 1: tolerated). The gene discussed is SLC5A5; the disease is hypothyroidism.