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What Causes Growth Hormone Deficiency? (continued from Written by a "mom" page- click here to see first page)
Growth Hormone Deficiency is caused by the inability of the pituitary gland to make enough growth hormone. This can be caused by genetic mutations such as growth hormone receptor gene, Prop-1gene, Pit-1 gene, hypothalamus, or other pituitary problems from injury etc. However, most children who fail to grow the minimum of 2 and a half inches per year (see What is Normal Growth? for Infants and pubertal children’s growth) have no easily identifiable reason for the pituitary failure. This is called Idiopathic Growth Hormone Deficiency.
Growth is a tremendously complicated process. I have provided some details later . Basically, growth hormone is secreted by the pituitary gland (often referred to as the Master Gland). The pituitary Gland is about the size of a pea! It is in a bony cave like area at the base of the brain. It is surrounded by a skin like membrane called the sellar diaphragm. (This is important-remember it for later).
Growth Hormone is only one of a number of hormones affecting a child's growth. If a child has thyroid or other hormone deficiencies those problems can also affect how he or she grows. (See Hypothyroidism or Panhypopituitarism for additional details).
When does Growth Hormone Deficiency Show Up?
Growth Hormone Deficiency may become evident at any time during childhood. Children are often partially growth hormone deficient. This means that their bodies make growth hormone but in different amounts. To explain this difference, let’s have 2 imaginary children.
Child # 1 is 10 months old. He made enough growth hormone to have “normal” growth for the first 10 months of life. After which, his growth began to slow down dramatically.
Child # 2 was in the normal ranges until the age of 5 but by the age of 6 he began to only grow 1 and a half inches each year.
Both children test growth hormone deficient, but for some reason Child #1 showed the signs of the problem much younger.
Why? Child #2 is able to make enough growth hormone to maintain a body the size of a 5 year old but no bigger. But Child #1 can’t make it to the age of 2. This would probably mean (unless there are other medical challenges) that Child #2 is not as growth hormone deficient as Child #1. Remember- both are deficient- but one is affected more than the other.
It is crucial to pay attention to a child’s growth curve to determine growth failure (see Growth Charts). Growth problems showing up on a growth chart can range from slight (little if any growth) to minimal. Normal puberty may be affected if other hormones or the hypothalamus is involved.
What exactly does growth hormone do?
In a Nutshell- Growth hormone is the key to all cell growth and reproduction. It helps the body maintain a healthy immune system, helps balance other hormones and body functions, helps to maintain muscle tissue (including the heart and lungs), it is essential for the body to be able to use up and get rid of fats instead of storing them, and helps the bones regenerate cells to stay healthy and strong as well as grow.
1. The primary function of growth hormone is to stimulate the liver and other tissues to secrete (make) IGF-1. (Remember above mentioned Insulin-like Growth Factor-1). IGF-1 essentially helps to make chondrocytes (cartilage cells) which in turn creates the bones to grow. IGF-1 also (in a nutshell) is important in muscle maintenance and growth.
2. Growth hormone binds to cells and depending on what type of cell it is- causes reactions. For example, when growth hormone binds to fat cells (adipocytes) it causes them to break down fats (triglycerides) in the body and blocks the body from holding on to and storing them.
3. Growth hormone is an essential component for every human alive. It helps the body maintain normal blood sugars and decreased oxidation of proteins.
What can affect how much growth hormone is made by the body?
Stress
Lack of Exercise
Sleep- The body makes and uses most growth hormone while sleeping. (Minimal levels during the day).
Hypothalamus- A region of the brain which stimulates GHRH. (Growth hormone-releasing hormone)
A stomach hormone called Ghrelin, binds to the somatotrophs and helps in the stimulation of growth hormone.
All of these things and still more all impact how a child grows! And they all have to be working together! Nutrition is the number one issue which can impact how well or poorly a child grows!
Characteristics of a Growth Hormone Deficient Child
It is important to keep in your mind that these characteristics are the “average” – as we all know- there are always exceptions. Please keep this in mind when reviewing the following information. And remember-it does not matter if mom is 54 foot tall and dad is 5 foot 4- if their son or daughter is NOT growing a minimum of 2 1/2 inches each year...they need to be evaluated.
Normal body proportions
Normal Intelligence
Tend to look younger than other kids their same age
May be a little chubby (there are many children who are the reverse of this who are growth hormone deficient)
Fail to growth a minimum of 2 ½ inches per year
What kind of doctor specializes in these types of problems?
Pediatric Endocrinologists-if you need a referral please contact the MAGIC office!
How do doctors tell if a child has growth hormone deficiency? What testing is involved?
The first thing doctors look at is the child’s growth chart. A thorough exam and family history will also be taken. Small children often come from small parents. However, with the new genetic discoveries, if a child is not growing 2 ½ inches per year-do not simply assume anything.
If they notice a change from one year to the next in how much that child is growing, or suspect a problem it is normal to order some blood work. They will be looking at:
- Thyroid Stimulating Hormone (TSH)- this hormone regulates body metabolism and is absolutely essential for normal growth.
- 2. Adrenocorticoptopic Hormone (ACTH)- this hormone tells the adrenal glands to make cortisol and other hormones which help the child’s body respond to stress. If a child has an elevated (too high) level of cortisol, it will cause growth failure.
- Luteinizing Hormone and Follicle Stimulating Hormone- these 2 hormones are what direct a girls ovaries or a boys testes to make sex hormones. Failure by these hormones affects puberty and growth.
- Vasopressin- is our body’s natural anti-diuretic hormone. This means that it controls how much water is released by the kidneys.
- IGF-1- Insulin-like Growth Factor is a new discovery (see brochure by clicking on link to the right)
- Rule out known genetic syndromes and conditions
The doctor will probably also order a bone-age. All this is – is an x-ray of your child’s hand.
This is a bit tricky-hang on! Remember when your children were babies? They had a soft spot on their skull that you had to protect until the skull bone grew up over the soft spot and closed it up. Well believe it or not, children have a similar area at the ends of all of their bones. They are called growth plates and the “soft spots" openings called epiphysis. This is the area where growth happens-not all over the bones like most people think.
A child who is 5 years old has a very large epiphysis opening compared to a 15 year old because there are years of growth left for the 5 year old. But the 15 year old has very small epiphysis because he is close, if not finished with growth.
X-ray technology can tell the doctor (with the information from the bone age x-ray) what their bone age is. If a child is 5 years old, a normal bone age would be around the age of 5. If there is a problem, the bone age might be at the age of 3 or worse, the age of 9 (early puberty called Precocious Puberty). So ordering some blood work and an x-ray are the 2 most common “beginning” tests towards finding out if a child has growth hormone deficiency or not.
If additional testing is needed, there are several different tests which may be used by pediatric endocrinologists. Some tests take a few hours; others may require a one night hospital stay. If your child gets to this “phase” you will likely hear the term “stim” test (parents often call it stem test). “Stim” is just a shortened version of the word stimulation. .
These "stim" tests involve IV's, (oh boy needle's - shots- could your day get any better?) some require slight exercize, and other really fun stuff (especially if you have to try and keep a 2 year old still with an IV attached to them) over the coarse of several hours. So be prepared to be an entertainer, and have something to entertain yourself in case your child takes a nap for this test. These tests sound a bit “trying” but are essential to a good diagnosis. What the doctor does is “trick” the body into thinking it is asleep (when growth hormone levels are at their highest). This gives everyone a really good idea as to the child’s true hormone deficiency
Most all pediatric endocrinologists will order an MRI of your child’s head. This is just a fancy (x-ray like) test fo their head to rule out tumors etc. Don’t panic if this test is ordered for your child! It is a standard test for children who are not growing normally and a good precaution. It is the exception-not the rule that anything will show up on this test. If your child's doctor ordered this test---good job so far!
Why do doctors test everything else before growth hormone deficiency?
Growth hormone levels are always changing in a child's body. But there are normal "ranges". The amount of growth hormone that a child's body is making can be affected by different things. And because this is a crucial and very powerful hormone it is really important to “rule things out” first. Let me explain with a brief example…say your child has a problem absorbing vitamins. If they did not rule other things out first, they would just assume it was growth hormone deficiency and start the medicine- but the child’s true problem would still be there and affecting other things. So this rule it out- method is actually a really good way to protect the health of children.
Ok---now that you have the basics of growth hormone you are ready for level 2---some medical details.
How does the body make growth hormone?
We have already established that growth hormone is produced by the pituitary gland at the base of the brain. The anterior section of the pituitary gland has cells called somatotrophs. These cells make, synthesize and store growth hormone (a protein hormone comprised of about 191 amino acids). (Note: the medical name for biosynthetic growth hormone....somatotropin! Makes sense now right?!)
The Good, the Bad and the Ugly
As the parent of a growth hormone deficient child, I can say from personal experience that my primary concern when my daughter was “first” diagnosed was her height. I knew she was NOT growing and that her younger sister was the same height. However, when I discovered that the treatments meant injections- I changed my thoughts. I figured- well I’m short, she will just be a little smaller than me….but that was BEFORE I learned more about it all. The real problem with a growth hormone deficient child is not what we (as parents) can see. It is what we cannot see that scared me to death! Therefore, if you are prepared to really learn about this problem- continue on- if you do not want to learn about life without the hormone-STOP now.
There is a document on the Internet written by one of my daughter’s pediatric endocrinologists, Dr. Steven Kemp. In it, he gives great detail about growth hormone deficiency. You can see the article yourself at this address; http://www.emedicine.com/PED/topic1810.htm
I have summarized one section here for you-
Mortality and Morbidity
Untreated Growth hormone deficient children have a higher risk of cardiovascular (heart) problems leading to cardiac death in adulthood.
Untreated growth hormone deficient patients as adults, have more fat, less muscle, higher risk of osteoporosis (bone mineralization is decreased), cannot tolerate exercise well, and cannot metabolize (get rid of) fats causing heart and other problems.
Age “Although most cases of idiopathic GHD are thought present at birth, diagnosis often is delayed until concern is raised about short stature.” The majority of children are identified with growth hormone deficiency around the age of 5 (when first starting school) or early puberty years when the gaps between these kids and their classmates become really noticeable.
Pathophysiology “12%-86% “(this is a pretty HUGE gap but I thought the information was worthy of putting in here) “of children with isolated” (idiopathic) “GHD have sellar developmental defects.”
Outlook - Whew! On to a more cheerful note!
Thanks to technology developed in the 1980's:
1. Parents don't have to travel to other states, stand in line and hope they reach the front of the line before the supply of medicine is completely gone for the next 3 months. There are amply supplies if children need this medicine.
2. Believe it or not- the cost has and is continuing to come down.
3. Most children who are IGF-1 or Growth Hormone Deficient, if diagnosed early enough can offset potential life long problems. Early diagnosis is the key. If your child has additional challenges, we have numerous written documents listed in the table on the right, We also offer online videos with Pediatric Endocrinologists and other experts, as well as personal testimonials from affected parents and children.
4. Unlike the days when I started on this road with my daughter, today there is a network of parents who have gone through this, ready, willing and available to talk with you. If you need help, please email or call us-that’s why we are here!
And finally- Trust your parental instincts- no one knows your child like you do! No one will fight for your child if you don't! Remember MAGIC's
Email us: ContactUs@magicfoundation.org
Call: (708) 383-0808 or 800-362-4423
MAGIC's Motto: Children have a short time to grow and a lifetime to live with the results.” © |
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