STAR (steroidogenic acute regulatory protein) is a mitochondrial protein that plays a crucial role in steroid hormone biosynthesis by mediating cholesterol transport from the outer to the inner mitochondrial membrane, where it serves as substrate for pregnenolone synthesis 1. STAR functions as a sterol transfer protein, with its cholesterol-transferring activity residing in the C-terminal region 1. This regulated transport is essential for initiating all steroid hormone production in steroidogenic tissues including the adrenal cortex and gonads 2. Biallelic STAR mutations cause lipoid congenital adrenal hyperplasia (LCAH), characterized by severe impairment of adrenal and gonadal steroidogenesis 2. Disease pathogenesis follows a two-hit model: first, impaired mitochondrial cholesterol import eliminates substrate for steroid synthesis; second, cytoplasmic lipid accumulation causes adrenal cell death and gland destruction 2. Loss-of-function mutations produce classic LCAH with severe early-onset disease, while partial-activity variants cause non-classic LCAH with milder, later-onset presentation featuring isolated adrenal insufficiency 2. Clinically, STAR deficiency manifests as primary adrenal insufficiency and 46,XY disorders of sex development, with good genotype-phenotype correlation established for described variants 2. STAR knockout animal models phenocopy the human condition, confirming STAR's essential regulatory role in steroid biosynthesis 1.