individual is inflicted by gigantism, it is the endocrine system that is being affected. Because it is the endocrine system that regulates the secretion of hormones in the body, it directly affects just about every other system in our bodies. From the reproductive system to the digestive system, it is the hormones released by the endocrine system that make everything function the way it is supposed to.

The growth hormone has two main functions when it comes to regulating various bodily functions in adults. It has both direct and indirect effects. To begin with, growth hormone, which is part of the endocrine system, binds onto receptor cells on the body part that it will directly affect. For example, the growth hormone will bind onto the fat cells which have growth hormone receptors, in order to make them function and break down triglyceride and suppress their ability to take up and accumulate circulating lipids (Waters & Kaye, 2002). The growth hormone also has indirect functions in an adult body. These indirect effects are mediated primarily by an insulin-like growth factor-I (IGF-I), a hormone that is secreted from the liver and other tissues as a response to growth hormone. This is actually what promotes the growth portion of this hormone because the IGF-I act on the target cells. Not only does growth hormone affect the growth in humans by stimulating the liver and other tissues to secrete IGF-I so that proliferation of cartilage cells results in bone growth and muscle growth, but it also has important effects on protein, lipid, and carbohydrate metabolism (Melmed et al., 2008).

Although this is a natural process that occurs automatically in the body, malfunctions could occur and cause an excess secretion of growth hormone. This growth hormone is modulated by many factors including stress, exercise, nutrition, sleep, and growth hormone itself, but its primary controllers are two hypothalamic hormones called growth hormone-releasing hormone (GHRH) and somatostatin (SS) and one hormone from the stomach, ghrelin (Bellone et al., 2002). Excess secretion of growth hormone could be due to lesions in either the hypothalamus, the pituitary, or in target cells. The effect that the out of control secretion of growth hormone could have on the body depends greatly on the age on onset, and can be caused by either a heritable or acquired disease.

Growth hormone has an anti-insulin activity because it suppresses the abilities of insulin to stimulate the uptake of glucose in peripheral tissues and it enhances glucose synthesis in the liver (Camacho & Savage, 2001). This leads to an excess level of insulin going through the body which is actually the cause of Diabetes Type 2. Because growth hormone is involved in carbohydrate metabolism, it complicates the relationship it has with insulin. For example, someone with an excessive amount of growth hormone will lead to an uncontrollable amount of insulin. Growth hormone doesn’t allow fat cells to absorb the insulin that it needs, which in a way could also be beneficial for those who are elderly and have diabetes. It reduces the amount of fat cells and therefore allows for a person’s glucose level to be regulated. The metabolism of fat is affected by growth hormone because it gets broken down and therefore allows it to travel freely throughout the body. This is what complicates the interaction between growth hormone and insulin (Rosenfalck et al., 1999).

Unlike dwarfism, gigantism is pretty difficult to treat. Gigantism is caused by an overproduction of growth hormone during childhood, right before the bone caps are sealed. This leads to an abnormal increase in height and is very rarely reversible. Dwarfism on the other hand, is an under-production of growth hormone and can be treated easier than gigantism because artificial growth hormone could be introduced into the body and could allow for more, or at least a more normal, height in a person. Gigantism is mostly treated by surgery since most of these cases are caused by tumors in the pituitary system (Melmed et al., 2008). But rarely can these individuals return to a normal height or be of a normal height. The over-production of growth hormone has so many other complications aside from height, that it makes gigantism a harder disease to combat than dwarfism.

Oxytocin is one of the hormones secreted by the pituitary. This hormone specifically affects the reproductive system in females as it is a main hormone in reproduction and in maintaining a healthy fetus (Waters & Kaye, 2002). Oxytocin is in a nine amino peptide that is synthesized in hypothalamic neurons and transported down axons of the posterior pituitary for secretion into the blood. Although oxytocin was known as being an “uncomplicated” hormone, with only a few well-defined activities related to birth and lactation, it actually has profound effects on the brain in relation to behavior. It does have a direct affect on the reproductive system though, especially in females when it comes to the actual process of giving birth to a child and in feeding it. It promotes lactation in women who breastfeed and is in charge of the “let-down” sensation when nursing. And most importantly, it is the oxytocin is the hormone that stimulates contractions of the uterine smooth muscle. In males however, oxytocin is present in the testes and can be detected during ejaculation which means that it facilitates transport from the male reproductive system to the female reproductive system (Waters & Kaye, 2002).

Another hormone secreted by the pituitary is the antidiuretic hormone which actually affects the excretory system as it is a key component in keeping the kidneys viable and hydrated for a person. It conserves body water by reducing the loss of water in urine. Antidiuretic hormone binds receptors on cells in the collecting ducts of the kidney and promotes reabsorption of water back into circulation. If this hormone wasn’t present, the collecting ducts are virtually impermeable to water, and it flows out as urine. This hormone also affects the vascular system since in many species, high concentrations of antidiuretic hormone cause widespread constriction of arterioles, which leads to increased arterial pressure (Melmed et al., 2008).

Although anabolic steroids and growth hormone basically do the same thing, they differ in the fact that growth hormone does more physical change, as in more muscle definition, while anabolic steroids does more acting change, as is more strength. In terms of actual difference when taken artificially (because although both are made naturally in the body, they are manufactured and produced as supplements), anabolic steroids are highly addictive, while growth hormone is not (Rosenfalck et al., 1999). Steroids are injected into the body, while growth hormone is an actual pill supplement. Growth hormone is also a more natural and therefore is safer than anabolic steroids.

References:

Melmed S, Kleinberg D., Kronenberg HM, Melmed S, Polonsky KS, Larsen PR. (2008) Anterior pituitary. In: Williams Textbook of Endocrinology. 11th ed. Philadelphia, PA: Saunders Elsevier; Chapter 8.

Rosenfalck A.M., Fisker, S., Hilsted, J., Dinesen, B., Volund, A., Jorgensen, J.O., Christiansen, J.S., & Madsbad, S. (1999). The effect of the deterioration of insulin sensitivity on beta-cell function in growth-hormone-deficient adults following hormone replacement therapy. Growth Hormone & IGF Research, 9(2), 96 — 105.

Waters MJ, Kaye PL. (2002) The role of growth hormone in fetal development. GH and IGF Res 12:137-146

Bellone S, Rapa A, Vivenza D, Castellino N. et al. (2002) Circulating ghrelin levels as a function of gender, pubertal status and adiposity in childhood. J Clin Endocrinol Investigation 25:RC13-15.

Camacho-Hubner C, Savage MO. (2001) Insulin-like growth factor-I deficiency. Horm Res 55 (Suppl) 1:17-20.

Hamilton, S. (1993) Looking back and up: At Robert Pershing Wadlow, the gentle giant. Illinois: Alton Museum of History and Art.

Growth Hormone