Homovanillic acid (HOC6H3(OCH3)CH2COOH; synonyms: 3-Methoxy-4-hydroxyphenyl acetic acid; HVA; 4-Hydroxy-3-methoxy-benzeneacetic acid; 4-Hydroxy-3-methoxyphenylacetic acid) is a major catecholamine metabolite. It is used as a reagent to detect oxidative enzymes, and is associated with dopamine levels in the brain.
Fasting plasma levels of HVA are known to be higher in females than in males. This does not seem to be influenced by adult hormonal changes, as the pattern is retained in the elderly and post-menopausal as well as transsexuals according to their genetic sex, both before and during cross-sex hormone administration. Differences in HVA have also been correlated to tobacco usage, with smokers showing significantly lower amounts of plasma HVA.