Subsequent to hormone binding, a signal is transduced to the interior of the cell, where second messengers and phosphorylated proteins generate appropriate metabolic responses.
The main second messengers are c AMP, Ca), and diacylglycerol (DAG).
In a separate but related system, exocrine tissues secrete their products into ducts and then to the outside of the body or to the intestinal tract.
Classically, endocrine hormones are considered to be derived from amino acids, peptides, or sterols and to act at sites distant from their tissue of origin.
When G-proteins bind to receptors, GTP exchanges with GDP bound to the α subunit of the G-protein.However, the latter definition has begun to blur as it is found that some secreted substances act at a distance (classical endocrines), close to the cells that secrete them (paracrines), or directly on the cell that secreted them (autocrines).Insulin-like growth factor-I (IGF-I), which behaves as an endocrine, paracrine, and autocrine, provides a prime example of this difficulty.Descriptive Table of Vertebrate Hormones Structure and Function of Hormones Receptors for Peptide Hormones Basics of Peptide Hormones The Hypothalamic-Pituitary Axis The Glycoprotein Hormone Family The Gonadotropins (LH, FSH, h CG) Thyroid Stimulating Hormone (TSH) Pro-Opiomelanocortin (POMC) Family Adrenocorticotropic Hormone, ACTH POMC-Derived Melanocortins & Feeding Behavior The Posterior Pituitary Hormones Vasopressin and Oxytocin The Growth Hormone Family Growth Hormone (GH) Human Chorionic Somatomammotropin (h CS) Prolactin (PRL) The Pancreatic Polypeptide Family: PP, PYY, NPY Melanin-Concentrating Hormone, MCH The Orexins Gastrointestinal Hormones and Peptides Adipose Tissue Hormones and Cytokines Irisin: Exercise-Induced Skeletal Muscle Hormone Natriuretic Hormones Renin-Angiotensin System Parathyroid Hormone (PTH) Calcitonin Family Erythropoietin, EPO The Pancreatic Hormones Insulin and Glucagon Somatostatin Amylin The integration of body functions in humans and other higher organisms is carried out by the nervous system, the immune system, and the endocrine system.The endocrine system is composed of a number of tissues that secrete their products, endocrine hormones, into the circulatory system; from there they are disseminated throughout the body, regulating the function of distant tissues and maintaining homeostasis.