Adult Growth Hormone Deficiency (AGHD)

By SWA

(AGHD) occurs when the pituitary gland does not produce enough growth hormone (GH) in adulthood. This deficiency can result from various causes, which are generally categorized into primary (pituitary) causes, secondary causes, and idiopathic causes (when the cause is unknown). Here are the main causes of AGHD:

1. Pituitary and Hypothalamic Disorders

  • Pituitary tumors: These are the most common causes of AGHD in adults. Tumors in or around the pituitary gland can disrupt GH production.
  • Surgical removal of pituitary tumors: Surgery to remove pituitary tumors may damage the gland, leading to reduced GH levels.
  • Radiation therapy: Radiation to the head or neck area, often used to treat pituitary or other brain tumors, can impair the pituitary gland's ability to produce GH.
  • Infections or inflammatory diseases: Conditions like sarcoidosis, tuberculosis, or meningitis can affect the hypothalamic-pituitary area, impacting GH production.
  • Trauma or injury: Traumatic brain injury (TBI) or severe head trauma can damage the pituitary or hypothalamus, resulting in AGHD.

2. Genetic and Developmental Causes

  • Congenital deficiencies: Some adults may have been born with a growth hormone deficiency that continues into adulthood.
  • Genetic mutations: Certain genetic mutations can impact the pituitary gland's ability to produce growth hormone.

3. Idiopathic Causes

  • Sometimes, the cause of AGHD is unknown. This is referred to as idiopathic growth hormone deficiency, where no identifiable cause (e.g., tumor, trauma, or genetic mutation) can be found.

4. Aging-Related Decline (sometimes considered a separate category)

  • GH levels naturally decline with age. Although not considered true AGHD, this age-related decline in GH can lead to symptoms that mimic GH deficiency. Some researchers consider it a potential contributing factor in cases where AGHD is diagnosed in older adults without other identifiable causes.

Summary

The main causes of AGHD are typically pituitary tumors or their treatment, traumatic brain injury, radiation therapy, and infections affecting the pituitary region. In some cases, it can also be congenital or idiopathic.

Treatment of AGHD generally involves growth hormone replacement therapy under the supervision of an endocrinologist.

Test for Adult Growth Hormone Deficiency?

Testing for Adult Growth Hormone Deficiency (AGHD) can be complex because growth hormone (GH) levels naturally fluctuate throughout the day. A single blood test is not enough to diagnose AGHD. Instead, doctors use a combination of stimulation tests, IGF-1 measurements, and sometimes imaging studies to evaluate GH deficiency. Here's an overview of the main tests used:

1. Insulin Tolerance Test (ITT)

  • Description: The Insulin Tolerance Test is considered the "gold standard" for diagnosing AGHD. It involves injecting insulin to induce a controlled drop in blood sugar (hypoglycemia), which should stimulate the pituitary gland to release growth hormone.
  • Procedure: Insulin is given intravenously, and blood samples are taken at specific intervals to measure GH levels. In healthy individuals, GH levels should rise in response to hypoglycemia. If GH levels do not rise adequately, it may indicate a deficiency.
  • Risks: The ITT can be risky, especially for people with heart disease or seizure disorders, as it intentionally lowers blood sugar to induce hypoglycemia.
  • Contraindications: Due to the risk of severe hypoglycemia, this test is not recommended for people with certain medical conditions, like cardiovascular disease or seizure disorders.

2. Growth Hormone-Releasing Hormone (GHRH) + Arginine Stimulation Test

  • Description: In this test, GHRH (a hormone that stimulates GH release) and arginine (an amino acid that also stimulates GH secretion) are given to trigger GH production.
  • Procedure: GHRH and arginine are administered intravenously, and blood samples are taken over time to measure GH response.
  • Advantages: This test is safer than the ITT and is often used if the ITT is contraindicated.
  • Limitations: The GHRH + arginine test is less commonly used in some regions and may be less sensitive in patients with hypothalamic dysfunction (since it bypasses the hypothalamus).

3. Glucagon Stimulation Test

  • Description: The Glucagon Stimulation Test is another alternative to the ITT and is often used if the ITT is contraindicated.
  • Procedure: Glucagon is injected intramuscularly, and blood samples are taken over several hours to measure GH levels. Glucagon stimulates GH release by indirectly influencing the pituitary gland.
  • Advantages: This test is safer and more tolerable than the ITT, with fewer risks of hypoglycemia.
  • Limitations: The glucagon stimulation test can be less sensitive than the ITT and requires a longer time commitment (up to 3 hours).

4. IGF-1 Level Measurement

  • Description: Insulin-like Growth Factor 1 (IGF-1) is a hormone produced in response to GH and reflects average GH levels over time.
  • Procedure: A simple blood test measures IGF-1 levels.
  • Advantages: IGF-1 levels are stable throughout the day, making it a convenient initial screening tool.
  • Limitations: Low IGF-1 can suggest GH deficiency, but normal IGF-1 levels do not rule it out. Thus, IGF-1 alone is not enough for a definitive diagnosis.

5. MRI of the Pituitary Gland

  • Description: Magnetic Resonance Imaging (MRI) of the pituitary gland and hypothalamus is often done to look for structural abnormalities, such as tumors or damage, that could cause GH deficiency.
  • Procedure: MRI imaging of the brain, specifically focusing on the pituitary region.
  • Advantages: This helps identify structural causes of AGHD, such as a pituitary adenoma or other pituitary/hypothalamic lesions.
  • Limitations: Imaging alone cannot confirm AGHD, but it can help identify the underlying cause if a deficiency is diagnosed.

Summary of Diagnostic Approach

  1. Initial Screening: Measure IGF-1 levels to screen for potential deficiency. If low, further testing is warranted.
  2. Confirmatory Testing: Perform a stimulation test (like the ITT, GHRH + arginine test, or glucagon stimulation test) to assess GH secretion.
  3. Imaging: If AGHD is diagnosed, an MRI of the pituitary gland is often recommended to check for structural abnormalities.

Important Notes

  • Diagnosis should be performed by an endocrinologist experienced in assessing GH deficiency, as interpreting these tests can be complex.
  • Some patients may need additional hormone testing to rule out deficiencies in other pituitary hormones, as AGHD can sometimes be part of a broader condition called hypopituitarism.

In Summary

AGHD diagnosis typically requires:

  • IGF-1 testing for initial assessment.
  • Stimulation tests (usually ITT, GHRH + arginine, or glucagon stimulation) for confirmation.
  • Pituitary MRI to identify structural causes if AGHD is confirmed.

This approach ensures an accurate diagnosis and helps in planning appropriate treatment, such as growth hormone replacement therapy.

references on testing and diagnosis of Adult Growth Hormone Deficiency (AGHD). These include medical guidelines, scientific articles, and trusted health organizations.

1. Endocrine Society Clinical Practice Guidelines on Growth Hormone Deficiency

  • Source: The Endocrine Society is one of the leading organizations for hormone-related health care, and they publish guidelines for the diagnosis and treatment of AGHD.
  • Title: "Diagnosis and Treatment of Adult Growth Hormone Deficiency: An Endocrine Society Clinical Practice Guideline"
  • Link: Endocrine Society Guidelines
  • Summary: This document provides evidence-based guidelines for diagnosing AGHD, including recommendations for stimulation tests like the ITT and the use of IGF-1 levels.

2. National Institutes of Health (NIH) - MedlinePlus

  • Source: MedlinePlus, a resource provided by the NIH, offers patient-friendly explanations about various health conditions, including AGHD.
  • Title: "Growth Hormone Deficiency"
  • Link: MedlinePlus Growth Hormone Deficiency
  • Summary: This page provides an overview of growth hormone deficiency, including causes, symptoms, diagnostic methods, and treatment options.

3. UpToDate: Evaluation and Treatment of Adult Growth Hormone Deficiency

  • Source: UpToDate is a highly regarded medical resource for healthcare providers, regularly updated with the latest research.
  • Title: "Evaluation and Treatment of Adult Growth Hormone Deficiency"
  • Link: UpToDate - Requires Subscription
  • Summary: This article covers diagnostic protocols, including the insulin tolerance test (ITT), alternative stimulation tests, and imaging recommendations. Note: Access to UpToDate may require a subscription or institutional access.

4. Journal of Clinical Endocrinology & Metabolism (JCEM)

  • Source: JCEM is a leading journal in endocrinology that publishes clinical and research articles on hormone-related conditions.
  • Article Title: "Growth Hormone Deficiency in Adults and Children" by Ho KK
  • Link: PubMed Abstract
  • Summary: This article reviews diagnostic criteria and the clinical relevance of GH deficiency in adults, focusing on various stimulation tests and the role of IGF-1 measurement. Access to the full article may require a subscription.

5. American Association of Clinical Endocrinologists (AACE) Guidelines

  • Source: The American Association of Clinical Endocrinologists provides evidence-based guidelines on hormone-related conditions, including AGHD.
  • Title: "AACE Medical Guidelines for Clinical Practice for Growth Hormone Use in Adults and Children"
  • Link: AACE Guidelines PDF
  • Summary: This guideline document includes recommendations for diagnostic testing in AGHD, covering the insulin tolerance test, glucagon stimulation test, and other diagnostic criteria.

6. Mayo Clinic - Adult Growth Hormone Deficiency Overview

  • Source: Mayo Clinic is a trusted source for reliable and accessible health information.
  • Title: "Growth Hormone Deficiency in Adults"
  • Link: Mayo Clinic - Growth Hormone Deficiency
  • Summary: This page provides an overview of adult GH deficiency, including causes, symptoms, testing, and treatment options, written in a way that's easy to understand for both patients and clinicians.

7. American Family Physician - Growth Hormone Deficiency in Adults

  • Source: American Family Physician is a peer-reviewed journal published by the American Academy of Family Physicians (AAFP).
  • Title: "Growth Hormone Deficiency in Adults: Diagnosis and Treatment"
  • Link: American Family Physician Article
  • Summary: This article is a comprehensive review of the diagnostic approach to AGHD, including descriptions of stimulation tests and IGF-1 measurement. It is aimed at family physicians and other healthcare providers.

Important Note:

While many of these resources are publicly accessible, some require subscriptions or institutional access (like UpToDate and full articles from JCEM). If you’re affiliated with a university or medical institution, you may be able to access these materials through your institution’s library.

For patients and general readers, resources like MedlinePlus, Mayo Clinic, and Endocrine Society guidelines provide reliable information that's easy to understand.

 © 2000-2025 Sieglinde W. Alexander. All writings by Sieglinde W. Alexander have a fife year copy right.
Library of Congress Card Number: LCN 00-192742 ISBN: 0-9703195-0-9

 

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