The function of FXYD1 (FXYD domain containing ion transport regulator 1, Ensembl gene identifier ENSG00000266964) is as follows. Associates with and regulates the activity of the sodium/potassium-transporting ATPase (NKA) which transports Na(+) out of the cell and K(+) into the cell. Inhibits NKA activity in its unphosphorylated state and stimulates activity when phosphorylated. Reduces glutathionylation of the NKA beta-1 subunit ATP1B1, thus reversing glutathionylation-mediated inhibition of ATP1B1. Contributes to female sexual development by maintaining the excitability of neurons which secrete gonadotropin-releasing hormone. {ECO:0000250|UniProtKB:O08589, ECO:0000250|UniProtKB:P56513, ECO:0000250|UniProtKB:Q9Z239}.