Diagnose of GH-deficiency: comparing the dietary-protein test with conventional Growth Hormone Stimulation Tests

Low GH concentrations are a characteristic for children who are too small for
their age. GH has a main function in linear growth and bodycomposition. Protein
ingestion stimulates the secretion of GH in adults. GH secretion after protein
ingestion is different between adult with growth hormone deficiency (GHD) en
adults without GHD. In order to determine whether a child is GHD or not, growth
hormone stimulationt tests are performed. Current tests are uncomfortable for
the children due to side effects and are on pharmacological basis, stimulating
GH release directly via only one single pathway in the complex physiological
regulation of GH secretion. Stimulation of GH release via one single pathway
results in the induction of a high inter individual variation in test outcomes.

To investigate if there is a correlation between the peak GH concentrations
after ingestion of gelatin protein and the peak GH concentrations after the two
standard tests (GHST) in order to discriminate between GHD and non-GHD.
To investigate the differences in coefficient of variation between the
different tests (arginine, clonidine, protein)
To investigate the frequency of side effects in the different tests (arginine,
clonidine, protein).

Three tests are perfomed in children who are too small for their age and meet
the inclusion criteria. The arginine and clonidine test are standard tests. The
protein test is new. All three tests are performed randomized on three
mornings.

Arginine-test:
The arginine test is one of the standard test to determine GH-deficiency in
children. The test is performed in the morning after an overnight fast.
Arginine hydrochloride (0.5 g/kg bodyweight) will infused for 30 minutes. Blood
samples are taken to measure growth hormone levels at -15, 0, 30, 45, 60, 75,90
and 120 minutes after the start of the infusion.

Clonidine test:
The clonidine test is one of the standard tests to determine GH-deficiency in
children. The test is performed in the morning after an overnight fast.
Clonidine (0,15 mg / m2) is ingested orally. Blood samples are taken to measure
growth hormone levels at -15, 0, 30, 45, 60, 75,90 and 120 minutes after the
ingestion of clonidine.

Protein test:
In this test subjects receive a protein drink, containing complete gelatin
protein with 8 lemon drops for the taste. Gelatin protein (Solugel LMC/3, PB
Gelatins GmbH, Nienburg/Weser, Germany) is a dietary protein and is found to be
the strongest GH stimulator among proteins [8].
For the protein test, subjects will arrive in the morning (08:00h) in fasted
state, they are instructed to drink and eat nothing after 22:00h the day before
the testday At 8:30h, subjects receive a drink, which contains 0.6 gram
protein per kg bodyweight in approximately 100 ml water. Blood samples are
taken every 20 minutes for 180 minutes to measure growth hormone levels.

The Arginine and Clonidine test are quite high in reliability, sensitivity and
specificity among the single pharmacological test, therefore these tests are
used in this study protocol to compare them with the alternative gelatin
protein test.
The GH-concentrations in all tests will be measured using an ultrasensitive GH
chemiluminescence immunoassay (Beckman Coulter, Harbor Blvd. Fullerton, U.S.A.)

Protein test:
In this test subjects receive a protein drink, containing complete gelatin
protein with 8 lemon drops for the taste. Gelatin protein (Solugel LMC/3, PB
Gelatins GmbH, Nienburg/Weser, Germany) is a dietary protein and is found to be
the strongest GH stimulator among proteins [8].
For the protein test, subjects will arrive in the morning (08:00h) in fasted
state, they are instructed to drink and eat nothing after 22:00h the day before
the testday At 8:30h, subjects receive a drink, which contains 0.6 gram
protein per kg bodyweight in approximately 100 ml water. Blood samples are
taken every 20 minutes for 180 minutes to measure growth hormone levels.

This research is neither beneficial nor harmful to the subjects. Allergic
reactions on gelatin protein are possible, but not common. In the screening,
test persons with a known allergy for gelatin protein are excluded. No
side-effect are mentioned in previous studies, using gelatin protein. There are
no further risks for the subjects in undergoing the standard clinical tests or
consuming the test-drink, as the standard clinical tests are used in hospitals
to determine GHDeficiency and the protein used are food-proof and present in
our daily diet. In our previous studies we used gelatin protein 0.6 g per kg
bodyweight and no adverse or side effects were found.
The blood sampling in this study does not include any other risks for the
subjects, apart from its usual risk of minor bruising.
This study is an non-therapeutic groups related study, with children from 6-10
years old. On forehand the study is performed in an adult GHD population. Since
a good diagnosis of GHD is important in children, in order to start GH therapy,
it is important to test the gelatin -test also in children to observe whether
the gelatin test shows a discrimination between GHD and non-GHD. Gelatin
protein will stimulate the GH secretion more physiological than the single
pharmacological tests will do. Furthermore no side effects are mentioned using
the gelatin test, while most of the single pharmacological tests know
side-effects.