Limitations And Caveats When Interpreting Gh Stimulation Tests
The responses to all GH stimulation tests show intra-individual variability, and the GH cut-points vary depending on the test used. For the ITT and GST, the cut-points advocated by previous consensus guidelines were 3-5 g/L and 2.5-3g/L, respectively . Other GH stimulatory agents such as clonidine, L-DOPA, and arginine are weaker GH secretagogues, and would require very low GH cut-points with utilization of sensitive GH assays to achieve adequate specificity . Hence, these tests are generally not recommended in the United States . Other limitations include the relative lack of validated normative data based on age, gender, BMI, glycemic status, and the paucity of data for specific etiologies of adult GHD that have recently been described, such as traumatic brain injury, subarachnoid hemorrhage, ischemic stroke, and central nervous system infections .
The Probability To Be Diagnosed With Ghd In Relation To Number Of Tests Performed
Children evaluated with one test only were more likely to be diagnosed with GHD compared with children evaluated with both tests . The association between being diagnosed with GHD or not and being evaluated by one or two tests was statistically significant both before and after adjustment for age, pubertal stage, priming and sex as analyzed in a regression model .
Table 1 Clinical characteristics of short children evaluated for possible growth hormone deficiency divided by number of GH tests performed together with data on whether GHD was diagnosed after testing.
Side Effects Of Medicines
- L-Arginine: This medicine can cause low blood sugar, which can make your child lightheaded or nauseated. Side effects from L-Arginine are rare and usually pass by the time your child goes home.
- Clonidine: Clonidine lowers blood pressure. The most common side effect is feeling dizzy and lightheaded. Your child should get up slowly after sitting or lying down and be extra careful climbing stairs. They should not go to school and should not play any sports, swim or exercise for the rest of the day. Activities that require them to be alert or have clear vision should be avoided. They may also feel very sleepy for a few hours or have dry mouth, dry eyes or blurry vision. These side effects can last up to 24 hours. Your child should be fine the following day after a good nights sleep.
- Glucagon: This medicine can cause low blood sugar, which can lead to nausea and vomiting. After the test is done, a snack or meal will help make your child feel better.
- Cortrosyn: Although rare, Cortrosyn can cause a flushing, warm feeling in the face and a metallic taste in the mouth.
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What Causes The Levels Of Growth Hormone To Rise
Growth Hormones are released by the pituitary glands at specific times, which makes it useless to get tested randomly. Getting tested at the wrong time can make a big difference and lead to abnormal results when dismissing normal daily variations. This hormone is at its peak in the morning. Its levels will be high after a workout or a stressful event.
Some drugs and medications can lead to false results. These include amphetamines, arginine, dopamine, estrogens, glucagon, histamines, insulin, levodopa, methyldopa and nicotinic acid. They can lead to higher levels of Growth Hormone. From another angle, drugs like corticosteroids and phenothiazines can lower this hormones levels. High doses of Biotin can also affect the levels of Growth Hormone.
When Is It Ordered
GH stimulation testing is ordered for a child with signs and symptoms of growth hormone deficiency, such as:
- A growth rate that slows down in early childhood
- Shorter stature than other children of the same chronological age despite normal or enhanced weight gain
- Delayed puberty
- Delayed bone development
Stimulation testing may be ordered for an adult when there are signs and symptoms of growth hormone deficiency and/or hypopituitarism, such as:
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How Is Follicle Stimulating Hormone Controlled
The production and release of follicle stimulating hormone is regulated by the levels of a number of circulating hormones released by the ovaries and testes. This system is called the hypothalamicpituitarygonadal axis. Gonadotrophin-releasing hormone is released from the hypothalamus and binds to receptors in the anterior pituitary gland to stimulate both the synthesis and release of follicle stimulating hormone and luteinising hormone . As per the definition of a hormone, the released follicle stimulating hormone is carried by the bloodstream and binds to receptors in the testes and ovaries.
In women, when FSH levels fall towards the end of the menstrual cycle. This is sensed by the hypothalamus, which produces more gonadotrophin-releasing hormone , which in turn stimulates the pituitary gland to produce more follicle stimulating hormone and luteinising hormone , and release these into the bloodstream. The rise in follicle stimulating hormone stimulates the growth of the follicle in the ovary.
As this follicle grows, it produces more and more oestrogen, which stimulates a surge in luteinising hormone and follicle stimulating hormone from the pituitary gland. This rise in LH leads to the release of an egg from the follicle, termed ovulation.
The Bottom Line On Hgh Deficiency Testing
Remember that diagnosis is just the first stage on the road to recovery. Advances in modern medicine allow for the prompt and effective treatment of HGH disorders in nearly all cases.When you visit our clinic, well take the time to discuss your concerns, order the necessary testing if our doctors suspect an HGH deficiency, and thoroughly review your results together to determine the next course of action.
Recovering your good health could be just a few weeks or months away. Thousands of patients across the US have discovered the rejuvenating promise of HGH replacement therapy. If you are experiencing a deficiency, then you could be one of the beneficiaries of therapy.
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Ask A Laboratory Scientist
This form enables patients to ask specific questions about lab tests. Your questions will be answered by a laboratory scientist as part of a voluntary service provided by one of our partners, American Society for Clinical Laboratory Science. Please allow 2-3 business days for an email response from one of the volunteers on the Consumer Information Response Team.
Difference In Reference Ranges At Different Laboratories
Reference ranges can differ between laboratories due to varying operating conditions, differing criteria for selection of healthy subjects, and different populations. Test results can be confusing, therefore it is important to speak to your physician if there is anything you dont understand or are concerned about.
Anti-aging panels can be carried out to determine if anti-aging treatment with bioidentical hormone replacement is required. For a full list of tests carried out in an anti-aging panel click for men and women.Imbalanced hormones cause a range of symptoms that can have a negative effect on your day to day life, but there is no need to suffer alone. Through comprehensive hormone testing, you can work with your doctor to pinpoint hormone imbalances. Private MD Labs can provide you with confidential laboratory testing to help you take charge of your own health. You can order your lab tests by clicking here or call us on 283-7882 for further information. By understanding your test results you can be proactive in your healthcare. However, even with a good understanding, hormone testing and test results can be confusing. Your doctor is there to explain your results and support you if you have any concerns or questions.
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Gh Test Protocol And Types
There are several different types of GH tests, and the specific testing protocol varies depending on which test your doctor orders.
As with all medical tests, its important to follow all of the preparation instructions from your healthcare team. In general, for GH tests, your doctor will ask you to:
- fast for a specific period of time before the test
- stop taking the vitamin biotin, or B7, at least 12 hours before the test
- stop taking certain prescription medications a few days before the test, if they might interfere with the test results
For some tests, your doctor may provide additional preparation instructions.
Its uncommon for people to have GH levels outside the typical range, so GH tests arent performed routinely. If your doctor thinks the levels of GH in your body may be abnormal, theyll likely order one or more of the following tests.
How Is The Test Used
Growth hormone testing is primarily used to help diagnose growth hormone deficiency and to help evaluate pituitary gland function, usually as a follow-up to other abnormal pituitary hormone test results.
GH testing is also used to detect excess GH and to help diagnose and monitor the treatment of acromegaly and gigantism.
Growth hormone is released in pulses, so a single measurement of the blood level is not normally clinically useful. Therefore, testing for the suppression or stimulation of growth hormone release from the pituitary is usually done.
Other tests that may be done include:
- IGF-1growth hormone stimulates the production of insulin-like growth factor-1 . IGF-1 is a hormone that carries out many of the effects of GH and helps promote normal bone and tissue growth and development. However, unlike GH, its level is stable in the blood throughout the day. This makes IGF-1 a useful indicator of average GH levels and the IGF-1 test is often used to help evaluate GH deficiency or GH excess.
- IGFBP3growth hormone also stimulates the production of IGFBP3 . The circulating level of this protein is also used as a measure of growth hormone action/activity and is especially useful in children younger than 3 years of age.
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Comparability Of Gh Assay Results
For many years external quality assessment schemes have documented large method- or laboratory dependent discrepancies between immunoassay results for several steroid- and peptide hormones. From this perspective, GH assays are only one unpleasant example of the difficulties in standardizing peptide hormone measurements . The problem has been reported for GH assays from studies in several countries in the past . The variability in concentrations reported for a single sample by different methods exceeds 100% in many cases. Obviously, this leads to problems when results from one study are compared to those from another study which used a different assay to measure GH concentrations. More relevant in clinical practice, this makes it impossible to compare GH assay results from one hospital to another when different assays and laboratories are used. Some studies directly compared results from different assays in the same clinical samples in one laboratory. In addition to confirming disagreement between results from different GH assays these studies also illustrated that the assay discrepancies affect the clinical interpretation of the results .
When Are Growth Hormone Tests Advised
GH deficiency or excess leads to GH disorders. Therefore, the doctor advises growth hormone tests when the patient presents the symptoms.
Acromegaly Symptoms in Adults:
Large hands, feet, and head.
Increase in growth compared to peers.
GH Deficiency Symptoms in Children:
Slow growth when compared to peers.
Short arms and legs.
Adults show symptoms of decreased bone and muscle mass.
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Other Hormone Tests Results
There are a huge range of hormone tests available and below are some that have not already been discussed.
Cortisol is a hormone produced in the adrenal glands that helps you manage stress, regulate blood sugar, regulate metabolism, fight infection, and maintain blood pressure. A disorder of your adrenal glands can make levels too high or too low.
Follicle Stimulating Hormone
The pituitary gland makes FSH which helps women to release eggs and men to produce sperm. Imbalances with FSH can cause infertility problems making it hard to get pregnant. It can also have an effect on puberty, periods, and sex drive.
LH regulates the function of the testes in men and ovaries in women. Imbalances in LH can result in fertility problems.
In women progesterone helps prepare your uterus for pregnancy, is part of breast development, and is part of breastfeeding. Low progesterone can cause problems such as mood swings, headaches, an irregular menstrual cycle, and weight gain. In men, progesterone is associated with sperm development.
Prolactin is present in both men and women and can play a role in sexual satisfaction. In women, it helps produce milk after childbirth. Prolactin plays an important role in reproductive health for both men and women.
Thyroid hormones help your body to breakdown fat, and to regulate and use energy.
What Are Growth Hormone Tests
The pituitary gland, a small pea-sized gland in the skull base, produces many vital hormones that regulate various body functions. Growth hormone , or human growth hormone, is one of the essential hormones produced by the pituitary, responsible for the normal growth of bones and muscles and aids in metabolism. High or low levels of growth hormones can lead to an imbalance in normal development. Therefore, growth hormone tests are done to determine GH levels in the body.
The levels of GH fluctuate throughout the day therefore, these tests determine the levels of proteins and hormones related to GH production.
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Clinical Consequences Of Poor Comparability Of Gh Assay Results
Poor comparability of GH assays has had significant clinical consequences, particularly for the diagnosis and monitoring of patients with GH deficiency and GH excess, acromegaly. The principal consequence is that no uniform GH criteria for these disorders can be developed so long as the assays remain heterogeneous.
Therefore, it is clear that determination of optimal GH criteria for both acromegaly and GH deficiency has been hindered by the current heterogeneity of GH assays. A further consequence of the inability to derive uniform criteria is that published criteria developed with one assay are often adopted to interpret GH levels measured with another in the research setting, in guidelines publications and in clinical practice. In the latter setting, the use of inaccurate criteria to guide clinical decision-making could, in some cases, lead to errors in clinical care. The adoption of criteria developed with one assay to use with another may also have actually hindered the development of more uniformity because of a false sense of security that these criteria could be utilized more generally. Until such a time when more uniformity of GH assay methodology is adopted and/or appropriate normative data for each assay are developed, published diagnostic GH criteria for acromegaly or GH deficiency can only serve as a general guideline. Some steps could improve more widespread use of published criteria in the meantime as outlined below.
Blood Tests For Growth Hormone Deficiency
In order to diagnose a growth hormone deficiency, a serum growth hormone test, sometimes referred to as a GH test, or HGH test. is used. The GH blood test measures the amount of growth hormone in your blood.
A blood test for growth hormone is a little more complicated than other standard blood tests that simply draw blood, and then have it analyzed for levels of whatever it is the diagnostician in looking for. It is more complex in testing blood for growth hormone, because your levels of growth hormone change throughout the day, so it is hard to get an accurate picture, simply by evaluating the growth hormone level in a given sample of blood.
This is why a specialized blood test for HGH level is given, known as a growth hormone stimulation test. A growth hormone stimulation test is used to see not only your level of growth hormone, but your bodys ability to produce HGH. In the growth hormone stimulation test, certain amino acids are introduced that should stimulate the pituitary to release growth hormone. A blood sample is then taken and tested to see if adequate amounts of HGH were released in response to the stimulation.
As we said earlier, if it is suspected that you may have a growth hormone deficiency, your doctor will likely also order an IGF-1 test. Unlike HGH, IGF levels remain more constant in the blood stream, and a simpler blood test is used to determine IGF-1 levels.
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Issues Related To Assay Calibration
5.2.1. Which calibrator should be used for GH assays?
Clearly, several problems with GH assays cannot be solved solely by using a single calibrator for all assays. Furthermore, it is important to keep in mind that the potency of standard preparations used for GH assays also can be affected by the way the reference preparations are treated to obtain the calibration solution used for the respective assay. E.g. the matrix of the assay specific calibrators is different between assays from different manufacturers. Commutability of immunoassay results is a complex task . It remains to be investigated to what degree the standardization of the standard alone will lead to better comparability of GH assay results .
Various Type Of Tests:
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