Effect of Adrenocorticotropic Hormone on Vascular Endothelial Growth Factor Release in Children Study
Condition: Adrenal Insufficiency; Osteopenia, Osteoporosis; Steroid Suppression of ACTH Secretion
MeSH terms: Osteoporosis; Bone Diseases, Metabolic; Adrenal Insufficiency
Study type: Interventional
Phase: Early Phase 1

Summary: 
      Bone disease and adrenal suppression are two of the many side effects of steroid use in
      pediatrics. Evidence has shown that adrenocorticotropic hormone (ACTH) protects against the
      adverse bone effects of steroids in animals and in vitro models, but this has not yet been
      evaluated in humans. The proposed mechanism in these studies is that ACTH stimulates
      osteoblasts in bone to release Vascular Endothelial Growth Factor (VEGF), which increases the
      vascularity in high risk areas of bone. This can potentially be protective against
      osteonecrosis and osteopenia, which can lead to bone fractures if not prevented. The VEGF
      release can also be used to demonstrate that an administration of exogenous ACTH occurred.
      This could be important in diagnosing adrenal insufficiency (AI). One of the tests to assess
      central AI is the low-dose ACTH stimulation test (LDAST). This test has a high rate of false
      positive results due to technical limitations. However, if an ACTH-stimulated VEGF level can
      be measured during the test as a marker of the test being done properly, it will allow for
      proper interpretation of the results (and identification of a false positive), which will
      reduce the number of patients being incorrectly diagnosed with central AI.

      This study will recruit ten healthy children and adolescents, ages 9-18, to assess the
      effects of ACTH on VEGF levels. The investigators will measure the response of VEGF and
      cortisol to an administration of a low dose and high dose of cosyntropin (the synthetic ACTH
      analog used in this test). The hypothesis of this study is that VEGF and cortisol will both
      increase after administration of cosyntropin. At this time, no other studies have
      demonstrated that VEGF is responsive to ACTH in humans. If the hypothesis is correct, the
      results will have two main implications. VEGF can be used as a marker of ACTH administration
      during the LDAST to identify false positive tests. Secondly, this will help further research
      into whether ACTH can be used to protect against bone disease in high-dose steroid-treated
      patients. Further studies can be done to assess whether this effect will be the same in
      patients with AI or steroid-induced adrenal suppression.
    

Detailed description: 
      Problem: Chronic steroid use causes a wide range of side effects, of which bone disease and
      adrenal suppression cause significant morbidity. Bone disease, which includes osteopenia,
      fractures, and osteonecrosis, is very common. In patients on chronic steroids, fractures can
      occur in up to 30-50%, low bone mineral density (BMD) can occur in up to 50%, and up to 40%
      have some degree of osteonecrosis. Another common side effect of steroid use is suppression
      of the HPA axis. This can cause a patient's endogenous cortisol and ACTH production to be
      reduced, which can take up to several months to return to baseline after discontinuing
      steroids. Diagnosing adrenal suppression can be difficult. Literature exists showing that
      ACTH can stimulate release of VEGF (in vitro and in animal in vivo studies), which can both
      be protective against bone disease and be used as a marker of exogenous cosyntropin
      administration. The primary goal of this study is to show that ACTH can increase VEGF levels
      in healthy humans.

      Bone disease: As stated above, patients taking chronic steroids are at high risk for
      significant bone effects. Glucocorticoids cause osteoblast apoptosis and decreased function
      while simultaneously decreasing apoptosis of osteoclasts, overall resulting in decreased bone
      formation and higher resorption. This leads to low BMD and fractures. Osteonecrosis can also
      be due to glucocorticoid causing decreased angiogenesis in high risk areas of bone (i.e. the
      femoral head). In rabbits,one study demonstrated that ACTH use protects against osteonecrosis
      by stimulating osteoblasts to release VEGF, which maintains good blood flow to these high
      risk areas of bone. Another study demonstrated that Cushing Syndrome patients with
      ACTH-producing pituitary tumors had less BMD loss than those with adrenal cortisol-producing
      tumors. This outcome points toward ACTH being protective against osteopenia (even in a high
      steroid state). The mechanism for this protective effect is unclear but could be through ACTH
      stimulation of VEGF. It is unknown whether ACTH increases VEGF in humans and if it does the
      dose needed and timeframe of the response need to be determined.

      Low-dose ACTH stimulation test (LDAST): There are several methods to evaluate adrenal
      insufficiency (AI), however the LDAST is best for diagnosing central AI and steroid-induced
      adrenal suppression (SIAS). The Metyrapone test is very specific, but it carries the risk of
      causing acute AI and requires a hospitalization to administer. The insulin tolerance test is
      the gold standard for diagnosing AI, but also carries the risk of causing hypoglycemia. The
      "standard" or high-dose (250mcg) ACTH stimulation test is a good test as well for diagnosing
      primary AI, but can result in false negatives that miss patients with central AI or SIAS,
      which can have significant morbidity (sensitivity for central AI is only 73%). Primary AI can
      also be diagnosed with an elevated ACTH level, but central AI and SIAS usually have a low to
      normal ACTH. Therefore, the LDAST test was created to help increase the rate of patients with
      central AI being diagnosed, with a sensitivity for central AI at 93%. However, there are
      several limitations to the LDAST. Cosyntropin is dispensed in 250 mcg vials, which is used
      for the high-dose test. and must be diluted to 1 mcg for the LDAST. The medication also runs
      the risk of sticking to IV tubing. Therefore, it is occasionally not truly given to the
      patient, which can cause a false positive result (the lack of cortisol response to ACTH is
      not due to AI, but due to never receiving cosyntropin). Due to these limitations, the
      specificity for diagnosing central AI is 90%. This can cause the interpreting physician to
      diagnose AI, and prescribe a hydrocortisone, when the patient did not truly have AI.

      If the LDAST had a positive control to show that the cosyntropin appropriately reached the
      patient, it would help to allow the endocrinologist to recognize a false positive result. As
      stated above, VEGF is stimulated by ACTH in animals. If VEGF levels were measured with
      cortisol levels, and they rose above a set threshold, the interpreting physician could feel
      more comfortable knowing that the test was administered appropriately. For VEGF to be a good
      control value, it would need to have a significant rise in response to cosyntropin, and would
      need to rise quickly and after one dose (the LDAST lasts one hour) and be independent of the
      cortisol response. In the in vitro study above, steroid-treated cells had significant rise in
      VEGF within one hour of ACTH treatment, and VEGF stayed elevated for up to four hours. In a
      study looking at whether VEGF could be a diagnostic biomarker to differentiate acute stroke
      in adults versus stroke mimics, there was a significant elevation of VEGF at the time of
      stroke presentation compared to the average normal value (peak median 1700 pg/mL with
      interquartile range of 1500-1900; baseline median 466 with interquartile range of 392-649).
      The mechanism for rise in VEGF was postulated to be due to a hypoxia stimulus in this case.
      However, it seems that VEGF can be acutely stimulated (potentially within one hour of a
      stimulus) and has the ability to rise to several standard deviations above the normal median
      baseline value in humans.

      VEGF: Vascular Endothelial Growth Factor is a cytokine glycoprotein that is responsible for
      angiogenesis, or the formation of new blood vessels. It can also maintain blood vessel
      density, thickness, and permeability, and it is vital for endothelial cell survival. VEGF is
      a family of cytokines, with VEGF-A being the prototype and most common. It is found in the
      lungs, kidneys, heart, adrenals, bone, brain, and several other organs. Within the adrenal,
      VEGF has been shown to be stimulated by ACTH and can be protective against atrophy in steroid
      use. Important in regards to this study, an animal study showed that VEGF can be stimulated
      by ACTH outside the adrenal glands, namely in osteoblasts in bone. Osteoblasts have an MC2R
      receptor that is stimulated by ACTH, leading to a rise in VEGF levels.
    

Intervention name(s): Low Dose Cosyntropin (ACTH) stimulation test; High Dose Cosyntropin (ACTH) stimulation test
Intervention type(s): Drug; Drug
Intervention description(s): Cosyntropin 1 mcg IV given to subjects at t=0; Cosyntropin 250 mcg IV given to subjects at t=60
Intervention MeSH terms: Adrenocorticotropic Hormone; Melanocyte-Stimulating Hormones; Cosyntropin; beta-Endorphin
Intervention model: Single Group Assignment
Intervention model description: At t=0, 9 ml of blood will be collected for measurement of VEGF, ACTH, and cortisol levels. Then, 1 mcg of cosyntropin (a synthetic ACTH analog) will be administered intravenously (IV). Samples for measurement of cortisol and VEGF levels will be obtained at t=30 and 60 minutes (6 ml of blood collected at both times). After the 60 minute blood draw, 250 mcg of cosyntropin will be administered IV. At t=90, 120, 150 , and 180 minutes, samples for measurement of cortisol and VEGF levels will be obtained (6 ml of blood collected at each time).
Masking: None (Open Label)
Primary purpose: Diagnostic
Keywords: steroid-induced adrenal suppression; vascular endothelial growth factor; adrenocorticotropic hormone; osteopenia