M al Kandari reported that three out of five patients developed hypothyroidism with homozygous frameshift mutation p.Ile154fsX248 (15), and a recent study reported hypothyroidism (TSH 10.61 mIU/L) in a neonatal FGD1 patient with compound heterozygous p.R145C/p.H238Y variant, but the repeated TSH levels without hormone replacement therapy at the age of 1.4 months were normal (16). Here, FGD1 is linked to hypothyroidism.