Abstract: Calretinin, also known as calcium retinal protein, is an important calcium-binding protein （CaBP）. CaBPs are important active substances in the nerve cells，which regulate the intracellular calcium ion concentration. Ca2+ is also the intracellular second messengers which in turn activates many physiological functions of enzymes or proteins in cells，such as the Ca2+-dependent protein kinase C and calcium calmodulin.Ca2+-CaBPs participate in a variety of cellular activities, including metabolism，skeletal muscle/cardiac contraction，nerve reaction impulse conduction. Calretinin predominantly expressed in the central nervous tissue，while it also expressed in some steroidogenic organs，such as testis （mainly in Leydig cell），ovary and adrenal. Function of calretinin in different tissues could be different，including regulation of hormonal production in cytoplasm，and regulatory effects on cell differentiation，development，proliferation and apoptosis. Effect of calretinin in reproductive endocrinology is a new area.

Key words: Neurons, Leydig cells, Ovary, Calretinin