Smith-Lemli-Opitz Syndrome: An autosomal recessive disorder of CHOLESTEROL metabolism. It is caused by a deficiency of 7-dehydrocholesterol reductase, the enzyme that converts 7-dehydrocholesterol to cholesterol, leading to an abnormally low plasma cholesterol. This syndrome is characterized by multiple CONGENITAL ABNORMALITIES, growth deficiency, and INTELLECTUAL DISABILITY.Dehydrocholesterols: Cholesterol derivatives having an additional double bond in any position. 24-Dehydrocholesterol is DESMOSTEROL. The other most prevalent dehydrocholesterol is the 7-isomer. This compound is a precursor of cholesterol and of vitamin D3.trans-1,4-Bis(2-chlorobenzaminomethyl)cyclohexane Dihydrochloride: An anticholesteremic agent that inhibits sterol biosynthesis in animals.Oxidoreductases Acting on CH-CH Group Donors: A subclass of enzymes which includes all dehydrogenases acting on carbon-carbon bonds. This enzyme group includes all the enzymes that introduce double bonds into substrates by direct dehydrogenation of carbon-carbon single bonds.Cholestadienols: Cholestadiene derivatives containing a hydroxy group anywhere in the molecule.Steroid Metabolism, Inborn Errors: Errors in metabolic processing of STEROIDS resulting from inborn genetic mutations that are inherited or acquired in utero.Sterols: Steroids with a hydroxyl group at C-3 and most of the skeleton of cholestane. Additional carbon atoms may be present in the side chain. (IUPAC Steroid Nomenclature, 1987)Cholesterol: The principal sterol of all higher animals, distributed in body tissues, especially the brain and spinal cord, and in animal fats and oils.StigmasterolDesmosterol: An intermediate in the synthesis of cholesterol.Syndrome: A characteristic symptom complex.Oxidoreductases: The class of all enzymes catalyzing oxidoreduction reactions. The substrate that is oxidized is regarded as a hydrogen donor. The systematic name is based on donor:acceptor oxidoreductase. The recommended name will be dehydrogenase, wherever this is possible; as an alternative, reductase can be used. Oxidase is only used in cases where O2 is the acceptor. (Enzyme Nomenclature, 1992, p9)Cholestenones: CHOLESTENES with one or more double bonds and substituted by any number of keto groups.Abnormalities, MultipleCholesterol, Dietary: Cholesterol present in food, especially in animal products.Intellectual Disability: Subnormal intellectual functioning which originates during the developmental period. This has multiple potential etiologies, including genetic defects and perinatal insults. Intelligence quotient (IQ) scores are commonly used to determine whether an individual has an intellectual disability. IQ scores between 70 and 79 are in the borderline range. Scores below 67 are in the disabled range. (from Joynt, Clinical Neurology, 1992, Ch55, p28)Anticholesteremic Agents: Substances used to lower plasma CHOLESTEROL levels.Disease Models, Animal: Naturally occurring or experimentally induced animal diseases with pathological processes sufficiently similar to those of human diseases. They are used as study models for human diseases.