Ketone bodies are produced by the process of ketogenesis, which occurs when acetyl-CoA accumulates beyond its capacity to be oxidized or used for fatty acid synthesis. Under these conditions, the thiolase-catalyzed reaction favors production of acetoacetyl-CoA (Figure 18.21), which is ultimately converted to the ketone bodies - acetoacetate, acetone, and -hydroxybutyrate.

-Hydroxybutyrate