Steroidogenic Effect of Insulin May Not Be Mediated Through Somatomedin-C/IGF-I Receptors

Insulin and Somatomedin-C/insulin-like growth factor-I (IGF-I) are capable of eliciting selective differentiative changes in ovarian granulosa cells of several species including growth promotion, enhanced steroidogenesis and induction of luteinizing hormone (LH) receptors (1–3). Insulin and IGF-I can also amplify the stimulatory effects of classical ovarian effector hormones and low-density lipoproteins (LDL) on progesterone (P4) biosynthesis in ovarian cells (3–5). IGF-I receptors have recently been shown to be present, and it is possible that the action of insulin may be mediated through the IGF-I receptors (2).