Stearoyl-CoA desaturase (SCD) is an enzyme involved in unsaturated fatty acid synthesis, primarily converting saturated fatty acids to monounsaturated fatty acids. The SCD family includes multiple subtypes, such as SCD1, SCD2, SCD3, and SCD4, with SCD1 being the most common in mammals. These enzymes are mainly located on the endoplasmic reticulum membrane and are expressed in tissues such as the liver, adipose tissue, and skin. SCD plays a crucial role in regulating lipid metabolism, cell membrane fluidity, and signal transduction. The specific expression and mutations of the genes are associated with various diseases, including obesity, diabetes, cardiovascular diseases, and cancer.