ReviewInsulin: Its role in the central control of reproduction

- Insulin plays a key role in the regulation of reproduction in addition to metabolism.
- Insulin regulates both pulsatile secretion and surge secretion of GnRH/LH.
- Insulin may be a signal in prenatal programming of adult reproductive function.
- Insulin targets in the brain include kisspeptin, AgRP and POMC neurons.
- Insulin resistance in human disease is associated with reproductive dysfunction.

Insulin has long been recognized as a key regulator of energy homeostasis via its actions at the level of the brain, but in addition, plays a role in regulating neural control of reproduction. In this review, we consider and compare evidence from animal models demonstrating a role for insulin for physiological control of reproduction by effects on GnRH/LH secretion. We also review the role that insulin plays in prenatal programming of adult reproduction, and consider specific candidate neurons in the adult hypothalamus by which insulin may act to regulate reproductive function. Finally, we review clinical evidence of the role that insulin may play in adult human fertility and reproductive disorders. Overall, while insulin appears to have a significant impact on reproductive neuroendocrine function, there are many unanswered questions regarding its precise sites and mechanisms of action, and their impact on developing and adult reproductive neuroendocrine function.