Homovanillic acid-d5 (Vanilacetic acid-d5) is the deuterium labeled Homovanillic acid (HY-N0384). Homovanillic acid (Vanilacetic acid) is a dopamine metabolite found to be associated with aromatic L-amino acid decarboxylase deficiency, celiac disease, growth hormone deficiency, and sepiapterin reductase deficiency[1].