Lesson 1.2.2

1.2.2 page 4

Human Growth Hormone

 

© Tiplyashin Anatoly/shutterstock

© Sandra G/shutterstock

 

 

The anterior pituitary regulates growth, muscle development, and fat metabolism through the production of human growth hormone (hGH), which ultimately affects every part of your body. Athletes are interested in using human growth hormone to improve performance because it stimulates protein synthesis and subsequent muscle development as well as toning of muscles. Overweight people are interested in using this hormone to fight obesity because it inhibits storage of fat and encourages its use for cellular respiration. At the same time hGH inhibits use of carbohydrates such as glucose. Older people are also interested in using hGH. As one ages, the levels of this hormone decrease - fat is harder to keep off and muscles become flabby. Testimonials, by aging stars, such as Sylvester Stallone, are prominent in advertisements for hGH. You will examine some of these ideas in the Thought Lab further in this lesson.

 

gigantism: a condition where a person produces excess hGH during childhood, resulting in a height of 8 feet or more

 

pituitary dwarfism: a condition where a person does not produce enough hGH during childhood, resulting in short stature

 

acromegaly: a condition brought about by excessive secretion of human growth hormone in an adult; hands, feet and nose widen and enlarge, jaw protrudes, voice becomes husky, barrel chest may develop, sweat glands enlarge, heart enlarges, high blood pressure may develop, enlarged tissues press on nerves, especially optic nerves causing loss of vision, particularly in the outer fields, and pressure on the brain causes severe headaches; there is an increased likelihood of developing diabetes mellitus

Nearly everyone is interested being tall. Girls usually imagine being swept away by a hero who is “tall, dark, and handsome”. Human growth hormone stimulates the growth plates at the end of the long bones and causes these bones to lengthen and increase a person’s height. Too much hGH during childhood causes gigantism. Today, Leonid Stadnyk is the tallest living person at a height of 2.57 m or 8 feet 5.5 inches. Too little hGH during childhood results in pituitary dwarfism. Thapa Magar, the shortest living person is only 50.8 cm or 20 inches tall. Emily, who you met earlier, had some minute tumors develop in the anterior pituitary several years after her final growth spurt. Instead of gigantism, she shows the symptoms of acromegaly. Because her growth plates have sealed, she cannot grow in height. Instead, her jaw has thickened, as have her ribs, and her fingers, toes, and nose have become enlarged.

 

Read

 

To learn more about human growth hormone and to summarize the functions and effects of this important hormone read pages 444 – 446 in your textbook. Figures 13.11 and 13.15 are good summaries that you may want to include in your course folder along with your notes.