Peptide hormones act as ligands for a wide range of G protein-coupled receptors. Peptide hormones are secreted and function in an endocrine manner to regulate many physiological functions, including growth, appetite and energy metabolism, cardiac function, stress, and reproductive physiology. Many signal via G protein-coupled receptors (GPCRs). Some examples include the growth-regulating hormones somatostatins and parathyroid hormone. Angiotensin plays a critical role in blood pressure regulation. Food intake, wakefulness, and energy homeostasis are all regulated by HCRTR2, the receptor for Orexin A/B. In addition, oxytocin is involved in the regulation of reproductive physiology and parent-child pair bonding after birth. In summary, peptide hormone-GPCRs encompass a broad range of physiological processes.