Wednesday, July 9, 2008

Testing 101: Testing Growth Hormone Levels in Adults


Ok...what's the big deal, anyhow? Why would anyone need to have their growth hormone levels evaluated? I'm going to stick to adults today because low growth hormone (GH) is a whole 'nuther ballgame with children.

As a review, growth hormone is secreted by the pituitary gland. Some pituitary tumors secrete too much GH which causes gigantism in children and acromegaly in adults. However, on the flip side, some tumors suppress the pituitary and too little is secreted. Even if the tumor does not do that, surgery to remove a tumor may cause the pituitary to quit or lessen it's secretion of GH. Radiation is also used on pituitary tumors that cannot be totally removed or if there is hyperplasia, and it, too, can damage the pituitary.

Adult Growth Hormone Deficiency (GHD) is a very real problem. GH maintains a healthy balance of muscle, bones, and fat and if an adult is deficient, her body composition changes. The body has less muscle, visceral fat is deposited around the abdomen, and bones weaken. Other fats in the body are affected. "Good" cholesterol (HDL) decreases but "bad" cholesterol (LDL) increases. This is very hard on the cardiovascular system (remember, the heart is a muscle) and the cerebrovascular system.

In Diagnosis of adult GH deficiency [V. Gasco, et al, Pituitary (2008) 11:121–128], the authors state:

Adults with growth hormone deficiency (GHD) have impaired health, which improves with GH replacement. GHD in adults leads to impairment in body composition and function, as well as to deranged lipoprotein and carbohydrate metabolism and increased cardiovascular morbidity. Based on evidence that GHD in adults is a
new syndrome which may benefit from GH replacement, health authorities in many countries have approved the therapeutic use of GH in hypopituitaric patients with severe GHD.

Not only is the physical health of a GHD adult affected. Social isolation, excessive tiredness, anxiety, depression, and apathy are also symptoms of GHD.

Ok, all of that to get to the testing part! Whew!

Growth hormone secretion is pulsatile which means random measurements of GH levels are not helpful or diagnostic. Since insulin-like growth factor-1(IGF-1) is stimulated by GH but does not fluctuate during the day like GH, it is useful in monitoring GH levels. Low levels are an excellent indication of a GHD problem. However, normal levels do not mean there is no deficiency.


The Growth Hormone Research Society met in 2007 in Australia and penned a consensus statement about the problems, testing, and treatments associated with adult GHD. In their consensus statement, they write:

...the patient with objective evidence of hypothalamic–pituitary disease (e.g., on imaging or after irradiation), who may present with organic isolated GHD as the first hormonal deficiency...may account for up to 25% of cases of GHD in the adult.

Consensus guidelines for the diagnosis and treatment of adults with GH deficiency II[European Journal of Endocrinology (2007) 157 695–700]

In this same consensus statement, they say:

Not all patients suspected of having GHD,however, require a GH stimulation test for diagnosis.Patients with three or more pituitary hormone deficiencies and an IGF-I level below the reference range have >97% chance of being GHD, and therefore do not need a GH stimulation test.

The Insulin Tolerance Test has, in the past, been the "gold-standard" for measuring true GHD. However, there have been some problems with its reproducibility and specificity.

In Clinical Presentation and Diagnosis: Growth Hormone Deficiency in Adults the American Journal of Managed Care [Volume 10:S424-S430 , October 2004 , Number 13 Suppl ] states:

Numerous pharmacologic agents can be used to assess GH production and secretion
by the pituitary in adults (Table 3). These include insulin, arginine, levodopa
(L-dopa), arginine plus L-dopa, arginine plus GHRH, and the glucagon test. None
display perfect sensitivity and specificity; however, the insulin tolerance test
(ITT) and arginine-GHRH are excellent tests.
The arginine-GHRH test is being used by major pituitary centers around the world. It is less stressful with less risk for the patient but yields reproducible and accurate results.

What are the differences in these two tests? In the ITT, the pituitary is provoked to produce GH by causing hypoglycemia in the patient with insulin. With the A-GHRH test, arginine is a somatostatin antagonist which essentially does the same thing. Combined with GHRH (to stimulate GH production), it is now the test of choice (see article linked above).

I had the arginine-GHRH stimulation test done this past spring at the University of North Carolina. There aren't many places to have this done on the east coast, yet. An IV was placed in my veins (after many attempts....I'm such a hard "stick") prior to the test. I had GHRH injected via an IV push, then Arginine was infused over a period of 30 minutes. My blood was drawn every 30 minutes afterwards for 3 hours and sent to Mayo Clinic labs to be tested. I received the following email a couple of weeks later, and my results were sent to my endocrinologist.

"You are definitely growth hormone deficient. Your starting GH value was 0.02ng/ml and your peak value was 0.13ng/ml."

I wasn't surprised. Neither was my endo.

13 comments:

  1. Most people today are taking growth hormone in homeopathic form because of its safety and gentleness.

    ReplyDelete
    Replies
    1. where can we get this, how do we access this on social security?

      Delete
  2. Any GH you swallow is destroyed by stomach acid. If only it was that easy...

    Beware of scams, Jane.

    ReplyDelete
  3. I am supposed to take this same test later this week or early next at a regular, but good hospital outside Philly, PA (Bryn Mawr Hospital). My endocrinologist says that they will have to order the drugs for the test--arginine, etc.--because they rarely perform this test.
    I am worried that they will do something wrong and the test results will say my pituitary is fine, despite the fact that 4 differnt labs over the years have repeatedly shown it to be abnormal--IGF-1 in the high 40s-low 50's. No measure GH at all after 1st morning draw.
    Do you really think the labs and the interpretation of results by Mayo Clinic really matter? If so, do you know a lab closer to me than North Carolina? Please advise, I am desperate to get it fixed, but I don't need a false positive to give my insurance an excuse not to pay! Thanks for any help you can send--DD

    ReplyDelete
  4. Hi, Anonymous! I'm sorry I just saw this. This test is easy to do and shouldn't be a problem. Please join us at the message boards at http://cushings-help.com . A direct link to the boards is http://cushings.invisionzone.com/index.php . You will have to register and login, but the folks there can help you so much!! Hugs, and I care!

    ReplyDelete
  5. Your IGF-1 levels are VERY LOW, and low IGF-1 levels in the setting of hypothalmic-pituitary disease suggest Growth Hormone Deficiency (GHD). You should check out www.ajmc.com (The American Journal of Managed Care: Clinical Presentation and Diagnosis: Growth Hormone). This website is excellent for diagnosing cause of GHD and also will help you interpret test results etc. Just make sure that wherever you get the test done, that they are highly skilled in this area. Good luck,

    ReplyDelete
  6. Before testing, always research thoroughly (on reputable websites) everything that you can about the test (ie do you need to fast, how much drug should hosp inject you with if it's a stim test, & the process) just to ensure that the test is done correctly. Stay proactive !

    ReplyDelete
  7. Thanks for the information and links...I am having the stimulation test next week. My IGF-1 levels were low on 2 occasions.

    ReplyDelete
  8. Is your endo in NC?

    ReplyDelete
  9. My endo is not in NC, but that was the closest place for me to have that stim test done. Right now, the GHRH is no longer available, so the arginine stim test is not done in most places. Some folks are substituting the glucagon stim test for it. The ITT is still a valid test for GHD, but it has a lot of risks that the glucagon does not.

    ReplyDelete
  10. Do you know anything about how common the Arginine only or Arginine plus L-dopa (levodopa) tests are these days, and how well they might be accepted by Insurance?

    I'm going to get one or the other of those tests. [I'm post pituitary adenoma surgery, with low-normal IGF-1]. I've considered asking my Insurance company if one or the other of those two testing protocols would be required or preferred over the other. But I'm hesitant to ask because I would not want them to come back and say that they'd require an ITT, for example.

    I know it probably depends on the Insurance company, but if you have any general info, I'd sure appreciate it.

    ReplyDelete
  11. Ok so my general blood work showed low growth hormone. So last week we did the glucogen shot drew blood every 30 minutes as well as blood sugars tested every 30 min, what is the name of the test and what are your blood sugars suppose to be during? I need to be educated on this badly!

    ReplyDelete
  12. Lorid1966, the GHRH for the arginine stim test is no longer available. The glucagon is the next best test. You should have GH levels tested during the test. I'm not sure about blood sugars.

    ReplyDelete

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