HSL ( hormone- sensitive lipase ) is an enzyme involved in hydrolysis of stored triglycerides and fatty acids; important for regulation of energy homeostasis. It has a long and a short form, generated by use of alternative translational start codons. The long form is expressed in steroidogenic tissues such as testis, where it converts cholesteryl esters to free cholesterol for steroid hormone production. The short form is expressed in adipose tissue, among others, where it hydrolyzes stored triglycerides to free fatty acids.