An Overview of the Biological Actions and Neuroendocrine Regulation of Growth Hormone
This chapter presents an overview of the biological actions of growth hormone and its neuroendocrine regulation. It aims to provide an introduction into the history of, and topics related to, the actions and regulation of growth hormone. In humans, there appears to be alternative splicing of growth hormone mRNA leading to a 20-kDa variant of growth hormone. Studies of serum levels of growth hormone have revealed discrete pulses with amplitude and frequencies that vary between species and within males and females of the same species. Growth hormone is a potent diabetogenic agent, producing hyperglycemia and an insensitivity to elevated levels of insulin, which results from decreased uptake and utilization of carbohydrate. The generally accepted model for regulation of growth hormone secretion proposes a dynamic interrelationship between somatostatin and growth hormone releasing hormone. The tripeptide thyrotropin-releasing hormone (TRH) can release growth hormone in cows and sheep, although in other species the action of TRH is controversial.