Module 2 Lesson 3 - 2
Lesson 3 — Human Growth Hormone
Human Growth Hormone
Read pages 444 - 446
The human growth hormone (hGH) is produced and stored in the anterior pituitary gland. The release of hGH is controlled through a negative feedback loop. The hypothalamus is stimulated to secrete the human growth hormone releasing hormone (hGHRH), which triggers the production of hGH in the anterior pituitary.
The anterior pituitary regulates growth, muscle development, and fat metabolism through the production of human growth hormone (hGH), which ultimately affects every part of the 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, human growth hormone (hGH) inhibits use of carbohydrates such as glucose. Older people are also interested in using human growth hormone (hGH) because, as one ages, the levels of this hormone decrease and fat accumulates and muscles become flabby.
Nearly every child is interested in how tall he or she is going to be. Human growth hormone stimulates the growth plates at the end of the long bones and causes these bones to lengthen and increase the person's height.
Disorder Related to Human Growth Hormone (hGH)
- Too much human growth hormone (hGH) during childhood causes gigantism. Robert Wadlow was the tallest person ever recorded at a height of 2.72 m or 8 feet 11 inches.
- Too little human growth hormone (hGH) during childhood results in pituitary dwarfism. Chandra Bahadur Dangi, the shortest person ever recorded, was only 57 cm or 21.5 inches tall.
- Over-production of human growth hormone (hGH) in adulthood, after the final growth spurt, results in acromegaly instead of gigantism. Because the growth plates have sealed, overproduction of hGH cannot result an increase in height. Instead, the soft tissue and bones widen. The jaw thickens as do the ribs, and the fingers, toes, and nose become enlarged.
To learn more about human growth hormone and to summarize the functions and effects of this important hormone, read pages 444 to 446 in your textbook.
Watch and Listen
To explore visually some interesting concepts about human growth hormone, watch the following segment of Biologix-09 on Growth Hormone (11 minutes):
Try This
Emily's husband had become very concerned about some of the symptoms that she had been exhibiting and the inability of several physicians to diagnose and treat whatever was wrong. Finally, a doctor determined what was wrong, but he provided Emily and her husband with only limited information. Her husband decided to do a online search before their next appointment.
What kind of information do you think her husband will find? Use the following information to guide your research. Define the health condition, explain the symptoms of the condition, and outline possible treatment.
- Emily is 30 years old.
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For the last several years she has suffered from numerous violent headaches.
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She has blurred vision, particularly to the sides.
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Her endocrine specialist confirmed that she has acromegaly. Do you agree?
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What causes acromegaly?
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Is treatment successful?
- Will acromegaly shorten Emily's life?
Try This Answer
In children, human growth hormone allows for the attainment of height programmed by the genes. The bones lengthen at growth plates on their ends. At the end of the growing period, these plates seal and no more growth is possible. In adults, too much growth hormone leads to radical changes in body appearance, but the changes occur so slowly that often they go unrecognized. Hands and feet become thick and wide. The forehead enlarges and the jaw juts. Spaces appear between the teeth. Blood pressure rises and the heart enlarges.
Headaches are a common sign of a pituitary tumor. Vision problems arise because the pituitary gland lies behind the optic nerve, and a pituitary tumor presses on the nerve and interferes with transmission of visual images to the brain.
Diagnosis of acromegaly is established by measuring blood growth hormone levels. A scan of the brain can detect clearly the presence of a tumour. Treatment consists of removal of the tumour, which can often be done with instruments passed through the nose or palate. When surgery is not feasible, medicines can dampen the production of growth hormone. Sometimes focused radiation therapy can shrink the tumour.
Emily might not have any noticeable physical changes associated with acromegaly. Her life will not be shortened.