Hydroxycarboxylic acid receptors are a family of G protein-coupled receptors (GPCRs) consisting of three receptor subtypes: HCA1, HCA2, HCA3. Hydroxycarboxylic acid receptors all play a role in the mediation of fat cell lipolysis. While most mammals have HCA1 and HCA2 receptors, only monkeys, apes, and humans have the HCA3 receptor. HCA2 and HCA3 receptors are thought to play a role in anti-inflammatory effects. Continued research is being done on the medical viability of hydroxycarboxylic acid receptors.