Basic Information:Growth hormone (GH), also called human growth hormone (HGH or hGH) or somatotropic hormone, somatotropin is a single polypeptide chain of 191 amino acids(qv) having two disulfide bonds, one between Cys-53 and Cys-165, forming a large loop in the molecule, and the other between Cys-182 and Cys-189, forming a small loop near the C-terminus. The structure of GH is shown in Figure 1; molecular mass is 22,125; the empirical formula is C990H1529N262O300S7.
Purified GH is a white amorphous powder in its lyophilized form. It is readily soluble (concentrations>10 mg/mL) in dilute aqueous buffers at pH values above 7.2. The isoelectric point is 5.2 and the generally accepted value for the extinction coefficient at 280 nm is 17, 700 (M?cm)?1, although other values have been reported. The equilibrium denaturation of GH has been studied. A two-state mechanism is indicated with a Gibbs free energy of unfolding of 60.7 ± 4 kJ/mol (14.5 ± 1 kcal/mol).
In solution, GH exists predominantly as a monomer, with a small fraction as a dimer and higher molecular weight oligomers. Under certain conditions, GH can be induced to form larger amounts of dimers, trimers, and higher oligomers although the conditions leading to self-association are not well understood. GH is a globular protein having approximately 55% α-helical character, a value determined independently in studies using circular dichroism and Raman spectroscopy. A protein of a high degree of homology and structural similarity is porcine growth hormone, the crystal structure of which has been solved. This structure shows four antiparallel helices connected by strands of polypeptide having little structure. A crystal structure of GH complexed with the extracellular domain of its receptor has been reported. In this complex, the structure of GH is readily obvious and shows the four-helical bundle connected in an up–up–down–down fashion rather than the more common up–down–up–down. This work has convincingly shown that GH possesses two binding sites for its receptor and that the hormone functions by dimerizing its receptor on the cell membrane.
The product should be stored at –20 °C. The lyophilized product remains active for one year at –20 °C. Upon reconstitution, the cytokine can be stored at 2–8 °C for short term only or at –20 °C to –80 °C in aliquots for long term. Avoid repeated freeze-thaw cycles.
Control of growth hormone release:Growth hormone release is not continuous; it is released in a number of ‘bursts’ or pulses every three to five hours. The pulsatile release of GH into circulation is regulated by the concerted actions of the hypothalamic hormones GH-releasing hormone (GHRH), which stimulates the pituitary to release growth hormone, and somatostatin (SST), which inhibits that release as well as by signals from the periphery ghrelin and leptin. In addition, one hormone called Ghrelin from the stomach binds to receptors on somatotrophs and potently stimulates secretion of growth hormone. The control process can be shown as follows:
On healthy people:A healthy supply of GH keeps you healthy psychologically—it maintains your sense of well-being, keeping you happy, engaged, and able to handle stress—and physically, keeping your heart healthy, your cholesterol levels down, inflammation down, bones solid. It even boosts your body’s ability to heal faster. But that doesn’t mean GH is right for every guy.
Studies of healthy adults taking human growth hormone are limited. Although it appears that human growth hormone can increase muscle mass and reduce the amount of body fat in healthy older adults, the increase in muscle doesn't translate into increased strength. It isn't clear if human growth hormone might provide other benefits to healthy adults.
Human growth hormone might cause a number of side effects for healthy adults, including:
1.Carpal tunnel syndrome
2.Increased insulin resistance
3.Swelling in the arms and legs (edema)
4.Joint and muscle pain
5.For men, enlargement of breast tissue (gynecomastia)
Human growth hormone might also contribute to conditions such as type 2 diabetes and heart disease and possibly an increased risk of some cancers.
Some research suggests that side effects of human growth hormone treatments might be more likely in older adults than in younger people. Because the studies of healthy adults taking human growth hormone have been short term, it isn't clear whether the side effects could eventually dissipate or become worse.
Preparation and Uses:Growth hormone was identified in the 1920s as a growth promoting factor. Scientists began to harvest GH from the pituitary glands of cadavers in the 1950s, but didn’t synthesize the first GH in laboratories until 1981, with its use as a performance-enhancing drug becoming popular shortly thereafter. By mid to late 1980s scientists were able to produce this 191-residue protein hormone in bacteria using recombinant DNA technology.
With the availability of large quantities of this recombinant hormone, therapeutic uses of growth hormone became possible. Children and adults with growth hormone deficiency can now be treated with growth hormone supplements. Also, patients suffering from diseases that lead to muscle wasting and weakness (like AIDS) also benefit from such supplements. However, in some cases these supplements are exploited to reverse symptoms of aging, to increase muscle mass in athletes and to increase the height of growing children. Used by athletes and weightlifters is banned. In the food industry, the cow and pig versions of this recombinant hormone protein are used to accelerate growth in farm animals. Although some concerns have been expressed regarding possible effects of consuming meat and milk from these animals, studies show that the growth hormone from these animals does not act on humans.
Other uses of GH, eg, for burns, wound healing, cachexia, osteoporosis, malnutrition, and obesity, are being investigated.
Using GH can cause some side-effects, which could include headache, muscle pain, joint pain, salt and water retention and rare instances of carpal tunnel syndrome (pain or tingling in the first three or four fingers of the hand). Children treated with the drug over the long term develop antibodies to it, but these do not seem to have any harmful effects.
China
