The hypothalamus is a small part of the vertebrate brain that contains a number of nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamus is located below the thalamus and is part of the limbic system. It forms the basal part of the diencephalon. All vertebrate brains contain a hypothalamus. In humans, it is about the size of an almond.
Pro-opiomelanocortin (POMC) is a precursor polypeptide with 241 amino acid residues. POMC is synthesized in corticotrophs of the anterior pituitary from the 267-amino-acid-long polypeptide precursor pre-pro-opiomelanocortin (pre-POMC), by the removal of a 26-amino-acid-long signal peptide sequence during translation. POMC is part of the central melanocortin system.
Somatostatin, also known as growth hormone-inhibiting hormone (GHIH) or by several other names, is a peptide hormone that regulates the endocrine system and affects neurotransmission and cell proliferation via interaction with G protein-coupled somatostatin receptors and inhibition of the release of numerous secondary hormones. Somatostatin inhibits insulin and glucagon secretion.
The paraventricular nucleus of hypothalamus is a nucleus in the hypothalamus, that lies next to the third ventricle. Many of its neurons project to the posterior pituitary where they secrete oxytocin, and a smaller amount of vasopressin. Other secretions are corticotropin-releasing hormone (CRH) and thyrotropin-releasing hormone (TRH). CRH and TRH are secreted into the hypophyseal portal system, and target different neurons in the anterior pituitary. Dysfunctions of the PVN can cause hypersomnia in mice. In humans, the dysfunction of the PVN and the other nuclei around it can lead to drowsiness for up to 20 hours per day. The PVN is thought to mediate many diverse functions through different hormones, including osmoregulation, appetite, wakefulness, and the response of the body to stress.
The tuberoinfundibular pathway refers to a population of dopamine neurons that project from the arcuate nucleus in the tuberal region of the hypothalamus to the median eminence. It is one of the four major dopamine pathways in the brain. Dopamine released at this site inhibits the secretion of prolactin from anterior pituitary gland lactotrophs by binding to dopamine receptor D2.
Ghrelin is a hormone primarily produced by enteroendocrine cells of the gastrointestinal tract, especially the stomach, and is often called a "hunger hormone" because it increases the drive to eat. Blood levels of ghrelin are highest before meals when hungry, returning to lower levels after mealtimes. Ghrelin may help prepare for food intake by increasing gastric motility and stimulating the secretion of gastric acid.
Neuropeptide Y (NPY) is a 36 amino-acid neuropeptide that is involved in various physiological and homeostatic processes in both the central and peripheral nervous systems. It is secreted alongside other neurotransmitters such as GABA and glutamate.
The median eminence is generally defined as the portion of the ventral hypothalamus from which the portal vessels arise. The median eminence is a small swelling on the tuber cinereum, posterior to and on top of the pituitary stalk; it lies in the area roughly bounded on its posterolateral region by the cerebral peduncles, and on its anterolateral region by the optic chiasm.
Releasing hormones and inhibiting hormones are hormones whose main purpose is to control the release of other hormones, either by stimulating or inhibiting their release. They are also called liberins and statins (respectively), or releasing factors and inhibiting factors. The principal examples are hypothalamic-pituitary hormones that can be classified from several viewpoints: they are hypothalamic hormones, they are hypophysiotropic hormones, and they are tropic hormones.
Agouti-related protein (AgRP), also called agouti-related peptide, is a neuropeptide produced in the brain by the AgRP/NPY neuron. It is synthesized in neuropeptide Y (NPY)-containing cell bodies located in the ventromedial part of the arcuate nucleus in the hypothalamus. AgRP is co-expressed with NPY and acts to increase appetite and decrease metabolism and energy expenditure. It is one of the most potent and long-lasting of appetite stimulators. In humans, the agouti-related peptide is encoded by the AGRP gene.
Neuroendocrinology is the branch of biology which studies the interaction between the nervous system and the endocrine system; i.e. how the brain regulates the hormonal activity in the body. The nervous and endocrine systems often act together in a process called neuroendocrine integration, to regulate the physiological processes of the human body. Neuroendocrinology arose from the recognition that the brain, especially the hypothalamus, controls secretion of pituitary gland hormones, and has subsequently expanded to investigate numerous interconnections of the endocrine and nervous systems.
The hypothalamic–pituitary–gonadal axis refers to the hypothalamus, pituitary gland, and gonadal glands as if these individual endocrine glands were a single entity. Because these glands often act in concert, physiologists and endocrinologists find it convenient and descriptive to speak of them as a single system.
Growth hormone–releasing hormone (GHRH), also known as somatocrinin among other names in its endogenous form and as somatorelin (INN) in its pharmaceutical form, is a releasing hormone of growth hormone (GH). It is a 44-amino acid peptide hormone produced in the arcuate nucleus of the hypothalamus.
The periventricular nucleus is a thin sheet of small neurons located in the wall of the third ventricle, a composite structure of the hypothalamus. It functions in analgesia.
Growth hormone secretagogue receptor(GHS-R), also known as ghrelin receptor, is a G protein-coupled receptor that binds growth hormone secretagogues (GHSs), such as ghrelin, the "hunger hormone". The role of GHS-R is thought to be in regulating energy homeostasis and body weight. In the brain, they are most highly expressed in the hypothalamus, specifically the ventromedial nucleus and arcuate nucleus. GSH-Rs are also expressed in other areas of the brain, including the ventral tegmental area, hippocampus, and substantia nigra. Outside the central nervous system, too, GSH-Rs are also found in the liver, in skeletal muscle, and even in the heart.
The central melanocortin system is defined anatomically as a collection of central nervous system circuits which include:
Hypothalamic–pituitary hormones are hormones that are produced by the hypothalamus and pituitary gland. Although the organs in which they are produced are relatively small, the effects of these hormones cascade throughout the body. They can be classified as a hypothalamic–pituitary axis of which the adrenal, gonadal, thyroid, somatotropic, and prolactin axes are branches.
Galanin-like peptide (GALP) is a neuropeptide present in humans and other mammals. It is a 60-amino acid polypeptide produced in the arcuate nucleus of the hypothalamus and the posterior pituitary gland. It is involved in the regulation of appetite and may also have other roles such as in inflammation, sex behavior, and stress.
Hunger is a sensation that motivates the consumption of food. The sensation of hunger typically manifests after only a few hours without eating and is generally considered to be unpleasant. Satiety occurs between 5 and 20 minutes after eating. There are several theories about how the feeling of hunger arises. The desire to eat food, or appetite, is another sensation experienced with regard to eating.
Pathophysiology of obesity is the study of disordered physiological processes that cause, result from, or are otherwise associated with obesity. A number of possible pathophysiological mechanisms have been identified which may contribute in the development and maintenance of obesity.
