Title: Hormones Affecting Hormonal Growth
Science Encyclopedia identifies eight growth hormones which are responsible for human growth. These are somatotropin, somatomedins, thyroid hormones, androgens, estrogens, glucocorticoids, insulin and genetics, the conditions of which either promote or inhibit the normal growth process. The presence of these hormones are normally measured by plasma levels in the blood- the more volume a hormone in the plasma is, the more active it is in doing its functions.
Of the eight hormones, Somatotropin, also called the major growth hormone (HGH) or synthetic growth hormone, is the most significant since “its presence in cells and tissues from birth to puberty (ages 13-19)” determines the growth pattern of an individual. HGH is a synthesis of several amino acids secreted by the anterior portion of the pituitary gland and is most responsible for linear skeletal and, cellular and fissial maturity. Most medical laboratories nowadays encourage the uses of HGH treatment to children and adults with growth hormone deficiency (GHD), a condition wherein the body does not produce the amount of growth hormone necessary for normal bone and muscle growth. The root cause of GHD is generally idiopathic or unknown although most scientific speculations and laboratory test experiments posit the presence of mutated genes or malformed pituitary glands as culprits. The general context of GHD is characterized by improper bone growth and muscle development which leads to short stature and underdeveloped muscles for children. This is a crucial concern because it delays puberty and causes underdeveloped bones and muscles, as well as, it induces the possibility of hypoglycemia or low blood sugar and seizures for children. To adults, symptoms of GHD includes the tendency of the adult to become overly fat, to have immature face, decreased bone and muscle density, and hence, reduced energy. Thus, to combat the problem, medical researchers developed the HGH treatment wherein patients with positive GHD are injected with HGH hormones to return their growth hormone levels. It is understood however, that HGH treatment would no longer promote growth after puberty.
Somatedins, like somatotropins, are proteins that function like insulin. These growth hormones are usually stimulated by the presence of hGH in the liver. There are two types of somatedins- the insulin-like growth factor I and II (IGF-I, IGF-II); while IGF-I is responsible for cartilage growth and collagen formation somewhere between ages 13 and 17, IGF-II is for fetal development and protein synthesis of RNA and DNA. Hence, the main function of somatedins is for cell growth and division, upon their stimulation by the somatotropins.
Thyroid hormones also affect human growth. James Norman, on his blog article entitled, “Your Thyroid Gland”, describes the functions of thyroid gland, a small gland located in front of the neck “under the control of the pituitary gland” and is responsible for “absorption and conversion of iodine into thyroid hormones, which regulate metabolism and growth in humans.” He describes how hyperthyroidism, a condition of the thyroid gland where it produces too much hormone and, hypothyroidism, when it secretes too little hormones, could exist. The effect of these conditions on human growth is apparent since abnormal secretion of thyroid hormones would significantly be accountable in gigantism (or over-tallness) or dwarfism (or over-shortness). Since thyroid gland follows a second-order control from the anterior pituitary gland (since the pituitary gland is regulated by the hypothalamus, the organ that regulates the endocrine system), it follows that the performance of the thyroid hormones depend heavily on the activity of hypothalamus regulators. There are certain cases when the hypothalamus does not function well, such as when the person is sickly, or when the presence of mutated genes is distinguished.
Androgen and estrogen hormones also play roles in human growth. According to Wikipedia, androgen, for instance, induces the secretion of fibroglast growth factor 8, or commonly called FGF8, a protein embedded in the FGF8 gene and which belongs to the fibroglast growth family, which is responsible mainly for “embryonic development, cell growth, morphogenesis, tissue repair, tumor growth and invasion.” When this gene is over-expressed, meaning, when it is overly produced, there is a tendency for the development of tumor and mammary cells in the male individuals. Likewise, estrogen, a hormone that induces sexual activity in both men and women (with greater volume in the female sex) also helps in the structural formation of bones, metabolism acceleration and promotion of protein bonds.
Lastly, the genetic make-up of an individual is considered to be a major element in human growth and development since the stature and growth pattern of an individual is usually dictated by the physical appearance of their parents.
References: 1. Growth Hormones – Normal Growth, Abnormal Growth, Aging And Growth
Hormone Therapy In Adults, Science Encyclopedia, [online]. Available at:
http://science.jrank.org/pages/3159/Growth-Hormones.html.
[Accessed 24 April 2011].
2. Norman, James. Functions of the Thyroid Gland, Endocrine Web, [online]. Available at: http://www.endocrineweb.com/conditions/thyroid/thyroid-gland-function. [Accessed 24 April 2011].
3. FGF8, Wikipedia, [online]. Available at: http://en.wikipedia.org/wiki/FGF8. [Accessed 24 April 2011].
4. Estrogen, Wikipedia, [online]. Available at: http://en.wikipedia.org/wiki/estrogen. [Accessed 24 April 2011].
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