A hormone is a biochemical molecule produced in any part of an organism and transferred to another part to influence a specific physiological process and therefore act as a messenger carried by the bloodstream to a different cell in the body where the message relayed is interpreted. A number of hormones in the body make up the endocrine system which is a control system made up of ductless glands which function to secrete hormones within specific organs. The endocrine system functions by providing an electrochemical connection from the hypothalamus part of the brain to all the organs that control the growth, development, metabolism, and reproduction of the body. The hormones found in the body of a human being are mainly divided into two types based on the site of action, these are local hormones and general hormones. The local hormones have specific local effect while the general hormones are mainly secreted by endocrine glands of specific origin and are later transported to influence physiological action through the bloodstream at distances which are remote from their cells of origin. The aim of this paper is to discuss the production process of growth hormones. The release of hormones is facilitated by glands of two main types namely the endocrine and exocrine glands.
Growth hormones make part of the endocrine gland hormones secreted by the pituitary gland (a part attached to the hypothalamus of the lower part of the brain). Consequently, pituitary gland consists of three main regions: the anterior pituitary gland/lobe (adreno-hypophysis/pars distalis), the intermediate lobe (pas intermedia), and the posterior pituitary gland/lobe (neuro-hypophysis/pars nervesa). The growth hormone is among the hormones produced by the anterior pituitary gland in response to a variety of chemical signals from the hypothalamus. The growth hormone is also called somatotropin or somatotrophic hormone (SH). The biochemistry of somatotropin is that it is a peptide whose molecular weight is 27000 with 191 amino acid residues consisting of 2 disulfide bridges between the adjacent cysteine (Cys) residues located at positions 153-164 and 181-188 respectively. Additionally, the N-terminal and the C-terminal residues of the hormone are phenylalanine (Phe) residues. The functionality of somatotrophic hormone remains distinct from other hormones of the anterior pituitary lobe in the sense that its effects are not due its influence on other endocrine glands but instead it acts directly upon a variety of tissues to produce a diversity of effects. The functions of the somatotrophic hormone include affecting the skeletal growth rate and the gaining of body weight. It also causes an abnormal increase in the amount of blood sugar by altering (by increasing) the production of degenerative changes in the islet of Langerhans (Rizza, Mandarino, & Gerich, 1982). Somatotropin also stimulates the growth of islet of Langerhans, this is referred to as the pancreatropic effect. SH also functions in controlling the production levels of fats in the body and their deposition in the liver, what is referred to as the ketogenic effect. During fasting, it prevents the release of muscle glycogen. Galactopoietic effect referring to the stimulation of the secretion of milk and mammary glands growth is another function of the somatotrophic hormone. Adrenal gland enlargement corticotropic effect is initiated by the growth hormone.
Studies have indicated that the production of the growth hormone is high in children and adolescents than in adults. At the latter stages, that is, the period between childhood to puberty the level of production of the somatotrophic hormone increases steadily, while at adulthood the production level reduces unless there is a condition that demands for an increase in secretion, for instance, gaining body weight. High levels of production of somatotropin cause a rapid increase in the rate of activity of the anterior pituitary lobe region to secrete the growth hormone. At higher levels, a negative inhibition mechanism occurs to prevent the excessive accumulation of the growth hormone in the bloodstream. A negative inhibition mechanism functions by reducing the physiological process and the metabolic production at the respective pathways involved in the augmentation of the secretion of a biochemical molecule.
According to Bilezikjian and Vale (1983), a rapid intensification in the production of cyclic ammonium monophosphate (cAMP) is associated with the stimulation of the secretion of the somatotrophic hormone by a synthetic growth-hormone regulating factor (hpGRF). The accumulation of cAMP to the extracellular medium in the body is also facilitated by the growth hormone (GH). Somatostatin functions by blocking the release of hpGRF-stimulated growth hormone while it partially attenuates the production of cAMP whether there is a phosphodiesterase inhibitor or not. Additionally, the release of the growth hormone is also inhibited by another compound known as verapamil in response to the hpGRF. The difference in the inhibition process of somatotropin and verapamil is that, unlike somatotropin, the inhibition effect of verapamil has no association with cAMP attenuation. Conversely, the presence of verapamil in the secretion of GH slightly increases the levels of intracellular cAMP; this provides an indication that a calcium ion is necessary for the release process of the hormone instead of the activating adenylate cyclase. Verapamil also blocks the release of the somatotrophic hormone in the presence of 8-bromocAMP. The exertion of inhibitory effects by cobalt chloride and cadmium chloride on the release of the basal and hpGRF-stimulated growth hormone provides an indication why the calcium ion is required. Therefore, it is worth noting that cAMP plays a critical role in the action of the growth regulator hormone factor as an intracellular mediator in somatotrophs. In addition, a calcium ion is an important component required during the release process of the growth hormone.
In other cases, other animal strains in culture have shown that the pituitary cells producing the growth hormone secrete another (second) protein hormone known as prolactin (Tashjian, Bancroft, & Levine, 1970). Prolactin as a protein hormone has a close function in the milk production process in the body of an organism, thus its secretion involves the enlargement of the mammary glands during lactation. The rate at which prolactin is secreted in the body varies proportionately with the amount of the growth hormone in the body such that the level a low proportion of prolactin in the bloodstream coincides with a high secretion amount of the growth hormone. The rates at which organisms produce prolactin along with the growth hormone (prolactin to growth hormone ratios) vary significantly based on a number of factors such as body surface area to volume ratio.
The production of the growth hormone augments by decreasing the amount of cortisol in the body. Cortisol is a biochemical molecule (a steroid hormone) that inhibits the production of the growth hormone; this occurs via the mechanism of an augmented density of the beta-adrenergic receptors along with resulting in adenyl cyclase and the release of somatostatin stimulation. With this effect, a compound referred to as pyridostigmine functions by reducing the tone of somatostatin in the hypothalamus, a situation which can be compared to the reversibility of the deficiency of the growth hormone in fibromyalgia on a physiologic basis. Fibromyalgia which is a condition affecting adults is responsible for their growth hormone deficiency; having diverse effects like increased morbidity, impairment in the quality of life, and in some instances death. The function of the growth hormone in adults with regards to fibromyalgia is maintenance of the muscle homeostasis. When an adult is suffering from a deficiency in the growth hormone production, then the likely signs and symptoms will include experiences like cold intolerance, low energy, dysthymia, muscle weakness, poor general health, decreased lean body mass, and reduced exercise capacity (Bennett, 2013).
In plants, the production of the growth hormones plays a significant role in explaining the process of growth and development of the plant at specific regions. The growth and development of the plant involve hormones which function in response to changes that occur during the gene transcription process. During gene transcription, the plant hormones act as the regulators of the process for consistency in growth. Plants growth occur mainly at two regions: the root and the shoot. Auxins are hormones responsible for the cell elongation of the root region on the ground to provide support to the plant. Cytokinins are plant hormones responsible for the cell division process essential in gene expression along with the auxins. Cytokinins also function to control the lateral growth of the shoot region of the plant (Davies, 2012; 2013). Interference with the growth genes of an organism alters the rate at which that organism grows and thus influences its development process.
References
Bennett, R. (2013). Growth Hormone Deficiency in Fibromyalgia.
BILEZIKJIAN, L. M., & VALE, W. W. (1983). Stimulation of adenosine 3, 5-monophosphate production by growth hormone-releasing factor and its inhibition by somatostatin in anterior pituitary cells in vitro. Endocrinology, 113(5), 1726-1731.
Davies, P. (Ed.). (2012). Plant hormones and their role in plant growth and development. Springer Science & Business Media.
Davies, P. (Ed.). (2013). Plant hormones: physiology, biochemistry and molecular biology. Springer Science & Business Media.
Rizza, R. A., Mandarino, L. J., & Gerich, J. E. (1982). Effects of growth hormone on insulin action in man: mechanisms of insulin resistance, impaired suppression of glucose production, and impaired stimulation of glucose utilization. Diabetes, 31(8), 663-669.
Tashjian, A. H., Bancroft, F. C., & Levine, L. (1970). Production of both prolactin and growth hormone by clonal strains of rat pituitary tumor cells. The Journal of cell biology, 47(1), 61-70.
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