IFIH1 and hypothyroidism: A splice donor variant in IFIH1 (interferon induced with helicase C domain 1), c.1641 + 1G > C (rs35337543, allele frequency 1.5% in European ancestry), is associated with a reduced risk of hypothyroidism in UK Biobank participants (OR 0.77 CI 0.70, 0.85; P = 5 × 10−9; Table 1).