RET and medullary thyroid gland carcinoma: Among 169 RET pathogenic variant carriers in UK Biobank, only 2 (1.2% [95% CI, 0.1%-4.2%]) had medullary thyroid cancer at recruitment, 1 with a high-risk variant and 1 with a moderate-risk variant (eTables 5 and 6 in Supplement 1).