Growth Hormone TestGrowth hormone GHalso known as human growth hormone Trenbolone acetate kura or somatotropin, is one of several hormones produced by the pituitary gland in your brain. GH plays a crucial role in normal human growth and development, especially in children and adolescents. GH levels that are higher or lower than they should be can lead to health problems in both children and adults. A serum growth hormone test GH test is used to measure the amount of GH in your blood. It is not a routine blood test, since abnormalities of Human growth hormone levels are typically higher when we are are uncommon.
9 Benefits of Human Growth Hormone (Along with Side Effects) - Dr. Axe
Growth hormone GH is a single-chain protein of amino acids with a molecular size of approximately 22kDa that is synthesized by and secreted from the somatotroph cells of the anterior pituitary gland. Encyclopedia of Neuroscience, Frohman, in Encyclopedia of Neuroscience , GH exerts a broad spectrum of effects, leading to the promotion of growth and the regulation of carbohydrate, lipid, protein, and mineral metabolism.
GH synthesis and secretion are regulated in a complex manner, primarily through the actions of hypothalamic neuropeptides that integrate hormonal, metabolic, and neurogenic signals.
Alterations in GH secretion lead to disorders of growth and metabolism. This article addresses the identification and structure of this critical hormone, its expression and regulation in the pituitary gland, its mechanisms of action, both peripherally and within the central nervous system, diseases of GH secretion, and the therapeutic use of GH.
Shunsuke Moriyama, in Handbook of Hormones , GH is a single-chain polypeptide containing two highly conserved intramolecular disulfide bonds that are important for biological activity. The actions of GH are initiated by its binding to a membrane-bound GHR that is located in various tissues, including the liver, muscle, adipose tissue, mammary gland, bone, kidney, and embryonic stem cells. GH in tetrapods as well as in fish is involved in the regulation of somatic growth primarily through the induction of IGF.
It is also implicated in metabolism, reproduction, immunity, and seawater adaptation. Recombinant human GH is used for treatment of GH deficiency and dwarfism. Growth hormone GH , secreted by anterior pituitary somatotroph cells, binds to hepatic GH receptors, initiating several intracellular signaling pathways resulting in IGF-I generation, cytoskeletal changes, alterations in glucose metabolism, and modulation of cell proliferation genes. Metabolic actions of GH also affect carbohydrate, protein, and lipid metabolism and alter body composition.
GH and IGF-I influence body composition, cardiovascular function, muscle strength, and exercise performance. Clinical evaluation of GH excess or deficiency requires estimation of GH responses to inhibitory or stimulatory factors, during provocative testing.
GH replacement therapy has beneficial effects in GH-deficient children with short stature and adults with GH deficiency. Short- and long-term actions of GH have been evaluated for potential beneficial effects in the aging population and for enhanced athletic performance by athletes, with lack of proven efficacy. Growth hormone GH , secreted by anterior pituitary somatotroph cells, binds to hepatic GH receptors, initiating several intracellular signaling pathways resulting in the generation of insulin-like growth factor IGF -1, cytoskeletal changes, alterations in glucose metabolism, and modulation of cell proliferation genes.
IGF-1, synthesized primarily in the liver, mediates most of the growth-promoting actions of GH. GH and IGF-1 influence body composition, cardiovascular function, muscle strength, and exercise performance. Clinical evaluation of GH excess or deficiency requires estimation of GH responses to inhibitory or stimulatory factors during provocative testing.
Adult and Pediatric Seventh Edition , Growth hormone GH secretion is regulated by a complex system involving two releasing hormones produced in the hypothalamus: GH-releasing hormone GHRH and ghrelin which is also produced in even greater quantities in the stomach , and one inhibiting hormone: In addition to their effects on the pituitary gland, these hormones interact with one another in the hypothalamus as well as being influenced by other neurotransmitters within the central nervous system.
Importantly, feedback mechanisms involving both GH and IGF-1 constitute another level of regulation of GH secretion and involves both the hypothalamus and pituitary gland. Gonadal, adrenal, and thyroid hormones also modulate the environment in both the hypothalamus and pituitary gland with resulting effects on the GH secretory response.
A schematic model of the main components of this regulatory system is shown in Figure In the remainder of this chapter, we will discuss relevant data associated with GHRH and ghrelin.
We have not emphasized data concerning somatostatin because this topic is covered in several chapters of this volume. Mahan, in Textbook of Nephro-Endocrinology , Growth hormone GH primarily exerts its somatotropic and metabolic effects by stimulating production of insulin-like growth factor-1 IGF-I Roelfsema and Clark, ; Pombo et al. Circulating IGF-I is released into the bloodstream as a result of liver production and functions as a classic endocrine hormone.
The production of GH and IGF-I and the important interactions of these two proteins are quite complex and are typically altered in individuals with renal insufficiency, with the degree of alteration variably affected by level of renal impairment, nutritional status, altered systemic hormones and sex steroids estrogen, testosterone Pombo et al.
Other potential consequences, such as decreased muscle mass, decreased bone mass, impaired neurocognitive development and disordered plasma lipids, may also develop and cause significant morbidity Mahesh et al. In adults with renal insufficiency, GH and IGF-I abnormalities have also been identified and may lead to decreased muscle mass, decreased bone mass, altered plasma lipids and altered metabolism Hirschberg and Adler, This represents an important new framework in the care of individuals with CKD.
The gene locus of human pituitary growth hormone GH is on the long arm of chromosome Apart from the normal gene GH-N , a highly homologous variant gene GH-V has been identified, which is expressed in the human placenta. The predominant pituitary GH form is a single-chain pure peptide of amino acids with two intramolecular disulfide bridges and a molecular mass of 22 kDa, designated 22K.
Additional heterogenous GH forms can be detected both within the pituitary and in the circulation. These include deamidated forms of 22K and oligomeric forms of both 22K and 20K, which represent native pituitary posttranslational modifications Baumann, The biological activity and role of 20K and the other heterogenous GH forms are unclear, wherefore this chapter will focus on the actions of monomeric pituitary 22K. Growth hormone is positively stimulated by growth hormone —releasing hormone and inhibited by somatostatin.
These hypothalamic-releasing factors are not usually measurable in the serum but act locally within the pituitary to provide pulses of growth hormone secretion throughout the day.
Growth hormone's biologic effects are mediated through insulin-like growth factor-1 IGF-1 produced in the liver and growth hormone itself. Growth hormone levels are labile, whereas IGF-1 levels represent an integrated growth hormone effect.
In men, onset of sleep, in concert with the first phase of slow-wave sleep, results in the largest growth hormone pulse of the day. Young premenopausal women demonstrate a slightly different pattern, with larger pulses during the day and a less prominent pulse with onset of slow-wave sleep.
Aging is associated with decreased levels of growth hormone and parallels decreases in slow-wave sleep, decreased responsiveness to GHRH, and increased somatostatin tone. Although there appears to be a circadian pattern of growth hormone secretion, the major determinant of growth hormone secretion appears to be the sleep-related increase in GHRH.
Ghrelin has been found to be an endogenous growth hormone secretagogue. Ghrelin administration has also been shown to increase slow-wave sleep and growth hormone secretion in humans. Growth hormone secretion is abnormal in a variety of illnesses. In acromegaly, a disease associated with elevated growth hormone and IGF-1 levels, there is loss of the usual pattern of an initial growth hormone spike at sleep onset. In addition, there are unpredictable spikes of growth hormone secretion throughout the day, with generally higher basal levels of secretion compared with normal.
Kate Felmet, Joseph A. Growth hormone is a large peptide hormone produced by the anterior pituitary. It is structurally similar to prolactin. Like prolactin, growth hormone has immune stimulatory effects and is suppressed by catecholamines.
It decreases glucose uptake and utilization and promotes differentiation. Growth hormone induces liver production of insulin-like growth factor-1, which mediates many of the effects of growth hormone. Growth hormone supports the immune response. Animal models suggest an important role for growth hormone in the development of the immune system.
In growth hormone —deficient humans, growth hormone increases the differentiation of B-cell and NK-cell activity. Like prolactin, growth hormone is produced by cells throughout the immune system. The hypercatabolic state seen in critically ill patients has been attributed in part to growth hormone dysfunction. Trauma, sepsis, and surgery are thought to induce a state of growth hormone resistance. The hyperglycemic catabolic state induced by growth hormone depletion and resistance is compounded by the normal stress response, the effects of immune-derived cytokines, and inadequate calorie delivery in the ICU.
Administering growth hormone perioperatively improves nitrogen balance, increases liver protein synthesis, increases muscle strength and lean body mass, and decreases postoperative fatigue over controls. Growth hormone also increases the rate of healing in burn patients and increases the rate of protein synthesis in sepsis and trauma patients.
Unfortunately, an elevated growth hormone level in critically ill patients is associated with increased mortality. In two large European studies of growth hormone use in critically ill adults, patients treated with growth hormone had a 1. Growth hormone -treated patients also had increased morbidity as measured by prolonged mechanical ventilation and longer ICU stay.
The reasons behind this association between elevated growth hormone and increased morbidity and mortality are not clearly understood. Growth hormone treatment is associated with an increase in blood glucose concentration, which may support bacterial growth. At very high levels, growth hormone binds in significant quantities to the prolactin receptor. Both of these hormones, at 10 to 20 times physiologic levels, may mediate immunosuppressive effects in vitro.
For more information on growth hormone and insulin-like growth factor in the ICU, the reader is referred to the excellent reviews by Carroll 67 and G. Gore, in Fundamental Neuroscience Fourth Edition , Growth hormone , or somatotropin, is a —amino acid protein that contains two disulfide bonds that give it a three-dimensional conformation that is necessary for its biological activity.
Release of the growth hormone is triggered by GHRH and is inhibited by somatostatin. The growth hormone plays a negative feedback role in the somatotropic axis, feeding back at the level of the GHRH neuron in the hypothalamus to inhibit GHRH mRNA levels and synthesis and stimulating somatostatin gene expression and release. Not only does the regulation of growth hormone involve the balance between GHRH and somatostatin, but it also involves other neurotransmitters and neuroactive substances, such as dopamine, vasoactive intestinal peptide, pituitary adenylate cyclase-activating peptide, TRH, galanin, neuropeptide Y, motilin, and interleukins.
In addition, other hormones, such as the thyroid hormone, glucocorticoids, sex steroid hormones, and metabolic fuels, can influence the release of growth hormone , highlighting the interwoven nature of the different neuroendocrine systems.
Cookies are used by this site. For more information, visit the cookies page. Growth hormone Growth hormone GH is a single-chain protein of amino acids with a molecular size of approximately 22kDa that is synthesized by and secreted from the somatotroph cells of the anterior pituitary gland.
Encyclopedia of Neuroscience, Related terms: Growth Hormone Vivien S. Herman-Bonert, Shlomo Melmed, in The Pituitary Third Edition , Growth hormone GH , secreted by anterior pituitary somatotroph cells, binds to hepatic GH receptors, initiating several intracellular signaling pathways resulting in IGF-I generation, cytoskeletal changes, alterations in glucose metabolism, and modulation of cell proliferation genes.
Bonert, Shlomo Melmed, in The Pituitary Fourth Edition , Introduction Growth hormone GH , secreted by anterior pituitary somatotroph cells, binds to hepatic GH receptors, initiating several intracellular signaling pathways resulting in the generation of insulin-like growth factor IGF -1, cytoskeletal changes, alterations in glucose metabolism, and modulation of cell proliferation genes.
Volume I John J. Adult and Pediatric Seventh Edition , Growth Hormone Secretion Growth hormone GH secretion is regulated by a complex system involving two releasing hormones produced in the hypothalamus: Growth Hormone John D.
Sleep Physiology Pierre Giglio, Ioana Dumitru, in Review of Sleep Medicine Second Edition , The Somatotropic Axis Growth hormone is positively stimulated by growth hormone —releasing hormone and inhibited by somatostatin.