The function of SULT1A3 (sulfotransferase family 1A member 3, Ensembl gene identifier ENSG00000261052) is as follows. Sulfotransferase that utilizes 3'-phospho-5'-adenylyl sulfate (PAPS) as sulfonate donor to catalyze the sulfate conjugation of phenolic monoamines (neurotransmitters such as dopamine, (R)- adrenaline/epinephrine, (R)-noradrenaline/norepinephrine and serotonin) and phenolic and catechol drugs (PubMed:8093002, PubMed:29524394, PubMed:14622112, PubMed:15358107). Catalyzes the sulfation of T4 (L- thyroxine/3,5,3',5'-tetraiodothyronine), T3 (3,5,3'-triiodothyronine), rT3 (3,3',5'-triiodothyronine) and 3,3'-T2 (3,3'-diiodothyronine), with a substrate preference of 3,3'-T2 > rT3 > T3 > T4 (PubMed:10199779). {ECO:0000269|PubMed:10199779, ECO:0000269|PubMed:14622112, ECO:0000269|PubMed:15358107, ECO:0000269|PubMed:29524394, ECO:0000269|PubMed:8093002}.