7ñ-Hydroxy-4-cholesten-3-one is an intermediate in the biochemical synthesis of bile acids from cholesterol. Its precursor, 7ñ-hydroxycholesterol, is produced from cholesterol by hepatic cholesterol 7ñ-hydroxylase (CYP7A1).
It is metabolized by the enzyme 7ñ-hydroxycholest-4-en-3-one 12ñ-hydroxylase to 7ñ,12ñ-dihydroxycholest-4-en-3-one and then to cholic acid, the major primary bile acid in humans. Alternatively, it can be converted into 5ò-cholestane-3ñ,7ñ-diol and then to chenodeoxycholic acid, the other major primary bile acid in humans.
Serum 7ñ-hydroxy-4-cholesten-3-one concentrations reflect the activity of the bile acid synthetic pathway. Serum 7ñ-hydroxy-4-cholesten-3-one values vary during the day as bile acid synthetic rates have a diurnal rhythm.
Elevated values are found in patients with bile acid malabsorption and may be useful in the diagnosis of this condition as high values are associated with low SeHCAT retention. The increase in serum 7ñ-hydroxy-4-cholesten-3-one concentrations reflects the loss of bile acids secondary to bile acid malabsorption or the increased synthesis found in primary bile acid diarrhea associated with impaired negative feedback of CYP7A1 by FGF19.