Fig. 3

Insulin receptor tyrosine kinases. The α subunit binds insulin and the β transmits a signal from bound insulin to the cytoplasm. The insulin signal activates the receptor’s protein kinases domain in the cytoplasm. Proteine kinases from the receptor phosphorylate insuline-response substrates triggering other chemical responses inside the cell. When IGFBPs binds and therefore activates the IGF-Ir, the hepatic synthesis of IGFBP-I is decreased, making IGF-I more biologically available, thus enhancing androgen production by theca interstitial and stromal cells