Involved in the final steps of cholesterol and steroid degradation (PubMed:28377529). Probably catalyzes the oxidation of the 5-OH group of (5R,7aS)-5-hydroxy-7a-methyl-1-oxo-2,3,5,6,7,7a-hexahydro-1H-indene-carboxyl-CoA, leading to the formation of HIEC-CoA (Probable). (5R,7aS)-5-hydroxy-7a-methyl-1-oxo-2,3,5,6,7,7a-hexahydro-1H-indene-carboxyl-CoA + NAD(+) = (7aS)-7a-methyl-1,5-dioxo-2,3,5,6,7,7a-hexahydro-1H-indene-carboxyl-CoA + H(+) + NADH Requires the presence of IpdC. Steroid metabolism; cholesterol degradation. Belongs to the short-chain dehydrogenases/reductases (SDR) family.