A Glimpse to Growth Hormone

“I was told I would never make it because I’m too short. Well, I’m still too short. It doesn’t matter what your height is, it’s what’s in your heart.”
- Kirby Puckett

This quotation by Kirby Puckett really inspires me and it comes across my mind whenever I hear comments about my height. Actually, when I was assigned to write about growth hormone, I got excited as I’m pretty interested about this topic because of my height. Being 4 feet, 11 inches tall, it seems like everyone is taller than me. And even though I’m already 19 years old, I still get called “kiddo” by others. I admit… I hate being short, but now I’m used to it though I’ll still jump high upon New Year’s Eve countdown (even if  to no avail, haha!).

Before, I always think that life is so unfair. Why are we not created equally, in terms of height? As they say, everything has a reason, ok? So where can we blame our height? Well, maybe we can blame it to the growth hormone… Here’s why…

Growth hormone (GH), secreted and stored by the somatotrophs in the anterior pituitary gland, is a 191 amino acid polypeptide hormone having two disulphide bonds. Also called somatotropin, growth hormone is an important hormone that stimulates the growth and development in humans. GH stimulates the liver and other tissues to produce insulin-like growth factor (IGF-1) which in turn stimulates the production of cartilage cells, facilitating bone and muscle growth. This hormone is responsible on how much growth one will have, depending on the level of its release in the body. It also participates in other complex physiologic processes such as in protein, fat, and carbohydrate metabolism.

What regulate the synthesis and secretion of GH? Two hypothalamic neuropeptides are responsible for this action. These neuropeptides are the growth hormone-releasing hormone (GHRH) and somatostatin (SS). GNRH stimulates both the synthesis and secretion of growth hormone. SS, in response to GNRH, inhibits the release of growth hormone and other stimulatory factors. Ghrelin, a peptide hormone secreted by the stomach, stimulates production of growth hormone by binding to receptors of somatotrophs. 

 

Too Much is Bad

Acromegaly is the result of overproduction of growth hormone that commonly presents during adulthood. The condition causes diffuse overgrowth of extremities, soft tissues, and organs. Other characteristic features of acromegaly include prognathism which is the bulging out of the lower jaw (mandible); spade-like hands; and frontal bossing. 

Acromegaly is caused by pituitary adenoma, a benign (non-cancerous) tumor in the pituitary gland. Pituitary adenoma raises GH level and also raises the level of IGF-1.

Can acromegaly be treated? Yes, it can be. Treatment includes surgery to remove the pituitary tumor, intake of drugs that block the action or lower the production of GH (i.e. octreotide, lanreotide, cabergoline, pegvisomant), and also radiation to destroy the tumor cells.

To further understand what acromegaly is, a YouTube video about the condition is presented below. Acromegaly was explained well by Dr. Frances Broyles of Swedish Medical Center.

Have you ever wondered how can one grow so tall, as in so tall, even up to 9 feet? It is because of the condition gigantism.

Excessive GH secretion that develops in adolescents or young children, that is before the closure of epiphyses, results to gigantism. The height of persons with gigantism falls between 7 feet (84 inches) and 9 feet (108 inches). Treatment is same with acromegaly.

To date, Sultan Kosen is the tallest man living as according to The Guinness Book of World Records. He measures 251 cm (8 ft, 3 in).

Sultan Kosen with He Pingping

Too Little = Too Short

Growth hormone deficiency (GHD) is a disorder that results when the pituitary gland does not produce enough growth hormone. In children, growth retardation or dwarfism is the major effect of the inadequate production of GH. An adult with a height less than 4 ft 10 inches (good thing I’m 4’11”) is considered a dwarf. Treatment for dwarfism includes surgery to correct bone problems, limb lengthening surgery, and hormone therapy in which the patient is injected with synthetic version of GH.

So, if there is the so-called ‘tallest man’, of course, there is a smallest man. The recognition goes to Chandra Bahadur Dangi. He holds the Guinness World Record for world’s shortest man living with a height of only 21.5 inches (54.6 centimeters). In our country, Philippines, there are even celebrities with dwarfism and they are known as Mahal, Mura, and Dagul.

In adults, GH is important to maintain the right amounts of body fat, muscle and bone. Adults with GHD may have reduced lean body mass, poor bone density, and may present emotional symptoms such as tiredness.

            GHD can be congenital or acquired after birth due to a tumor, brain injury, or radiation treatment to the head.

Chandra Bahadur Dangi

Tests Used to Diagnose GH Disorders

Here are some of the tests used to detect problems in GH release:

o        IGF-1 :

This test is a blood test used to determine the levels of IGF-1. As I stated above, IGF-1 is produced by GH, that means it can be used to determine the extent of GH release.

o        Oral glucose tolerance test:

Maybe you are thinking that OGTT is only used to diagnose instances of diabetes mellitus. Well, think again. OGTT can also be used in the diagnosis of GH disorders. It is a GH suppression test in which GH levels in the blood are measured after the intake of glucose solution. The glucose solution will inhibit the pituitary gland from producing GH. However, in patients with acromegaly, the GH level will not change because the pituitary tumor that produces GH will not stop releasing GH.

o        Insulin Tolerance Test:

A GH stimulation test regarded as the “gold standard” for measuring GHD. In this test, the pituitary gland is stimulated to produce GH by causing hypoglycemia. Other GH stimulants are arginine and clonidine.

o       Computed Tomography (CT) and Magnetic Resonance Imaging (MRI)

Images from these imaging tests may reveal a brain tumor which can be of help in the diagnosis of GH disorders.

So, that’s it. These are just some of the facts regarding growth hormone. I started this blog post with an inspiring quotation and I also want to end it with another quotation:

“It’s not the size of the dog in the fight, It’s the size of the fight in the dog.”

-          Mark Twain

*Thanks for reading my blog! I hope you learned something. God bless J

Oh by the way, take a look at these funny meme comics.... hahaha!

References:

McPherson, R.A., Pincus, M.R. Henry’s Clinical Diagnosis and Management by Laboratory Methods. 22^nd Edition. 2011

Bishop, M.L., et al. Clinical Chemistry: Techniques, Principles, Correlations. 6^th ed. 2010

Rosenbloom AL, Connor LE. Hypopituitarism and other disorders of the growth hormone-insulinlike growth factor I axis. In: Lifshitz F (ed), Pediatric Endocrinology, 3rd ed, New York, Informa Health Care 2007; 65-101.

Abrams RL, Parker ML, Blanco S, Reichlin S, Daughaday WH. Hypothalamic regulation of growth hormone secretion. Endocrinology 1966;78:605-613.

Photo credits:

https://en.wikipedia.org/wiki/File:Endocrine_growth_regulation.svg

http://www.netterimages.com/image/5748.htm

http://www.telegraph.co.uk/news/picturegalleries/howaboutthat/6988398/The-worlds-tallest-man-Sultan-Kosen-and-the-shortest-man-in-the-world-He-Pingping-meet.html

http://www.nwchc.com/body.cfm?xyzpdqabc=0&id=6&action=detail&AEArticleID=100146&AEProductID=Adam2004_1&AEProjectTypeIDURL=APT_3##

http://www.tumblr.com/tagged/shortness

Video Credits:

http://www.youtube.com/watch?v=AX48MPIDyYw