Cells produce GHB by reduction of succinic semialdehyde via succinic semialdehyde reductase (SSR). This enzyme appears to be induced by cAMP levels, meaning substances that elevate cAMP, such as forskolin and vinpocetine, may increase GHB synthesis and release. Conversely, endogeneous GHB production in those taking valproic acid will be inhibited via inhibition of the conversion from succinic acid semialdehyde to GHB. People with the disorder known as succinic semialdehyde dehydrogenase deficiency, also known as γ-hydroxybutyric aciduria, have elevated levels of GHB in their urine, blood plasma and cerebrospinal fluid.