Growth hormone deficiency laboratory findings

Growth hormone deficiency Microchapters
Home
Patient Information
Overview
Historical Perspective
Classification
Pathophysiology
Causes
Differentiating Growth hormone deficiency from other Diseases
Epidemiology and Demographics
Risk Factors
Screening
Natural History, Complications and Prognosis
Diagnosis
Diagnostic Criteria
History and Symptoms
Physical Examination
Laboratory Findings
X Ray
CT
MRI
Echocardiography or Ultrasound
Other Imaging Findings
Other Diagnostic Studies
Treatment
Medical Therapy
Surgery
Primary Prevention
Secondary Prevention
Cost-Effectiveness of Therapy
Future or Investigational Therapies
Case Studies
Case #1
Growth hormone deficiency laboratory findings On the Web
Most recent articles
Most cited articles
Review articles
CME Programs
Powerpoint slides
Images
American Roentgen Ray Society Images of Growth hormone deficiency laboratory findings All Images X-rays Echo & Ultrasound CT Images MRI
Ongoing Trials at Clinical Trials.gov
US National Guidelines Clearinghouse
NICE Guidance
FDA on Growth hormone deficiency laboratory findings
CDC on Growth hormone deficiency laboratory findings
Growth hormone deficiency laboratory findings in the news
Blogs on Growth hormone deficiency laboratory findings
Directions to Hospitals Treating Growth hormone deficiency
Risk calculators and risk factors for Growth hormone deficiency laboratory findings

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mohammed Abdelwahed M.D[2]

Laboratory Findings

Neonatal and children evaluation

Testing in the neonate

A GH level should always be measured

in the presence of neonatal hypoglycemia in the absence of

a metabolic disorder. A random GH measurement in a polyclonal

RIA of less than 20 mg/L would suggest GHD in the

newborn. An IGFBP-3 measurement is of value for the diagnosis

of GHD in infancy.

Children evaluation

Criteria to initiate immediate investigation include

1) severe short stature, defined as a height more than 3 sd

below the mean;

2) height more than 1.5 sd below the midparental

height;

3) height more than 2 sd below the mean and

a height velocity over 1 yr more than 1 sd below the mean

for chronological age, or a decrease in height sd of more than

0.5 over 1 yr in children over 2 yr of age;

4) in the absence of short stature, a height velocity more than 2 sd below the

mean over 1 yr or more than 1.5 sd sustained over 2 yr; this

may occur in GHD, presenting in infancy, or in organic

acquired GHD;

5) signs indicative of an intracranial lesion;

7) neonatal symptoms and signs of

GHD.

The evaluation for GHD in a short child, where short stature is defined as a height more than 2 sd below the population mean, should not be initiated until other causes of growth failure, such as hypothyroidism, chronic systemic disease, Turner syndrome, or skeletal disorder, have been considered and appropriately excluded.

GH secretion is pulsatile and its secretion is regulated by two hypothalamic factors; growth hormone releasing hormone and somatostatin.

So, measurement of a random serum GH level alone is not helpful and usually other tests used with it:

• Insulin-like growth factor I (IGF-I)
• Insulin-like growth factor binding protein-3 (IGFBP-3) levels: it is the major serum carrier protein for IGF-I and the most GH dependent.

• Their concentrations often reflect the concentration of secreted GH.They are better tests than GH level because they are stable during the day and not pulsatile.

Limitations

Serum IGF-I levels may be low in conditions other than GHD such as growth hormone insensitivity, hypothyroidism, renal failure, diabetes, and cancer.

Interpretation

• Reduced level of IGF-I and IGFBP-3 with delayed bone age: provocative GH testing is needed. If the growth failure is severe and IGF-I and IGFBP-3 are severely low, there is no need to perform GH stimulation testing.

• Normal IGF-1 and IGFBP-3: no further testing is required.

GH stimulation tests

• It is indicated for most patients suspected to have GHD.
• The results should be interpreted in the context of auxological findings, bone age, and IGF-1 and IGFBP-3 concentrations.

• If the clinical and other laboratory criteria are sufficient to make the diagnosis of GHD, there is no need to perform the test. 

• A serum GH concentration of >10 mcg/L, but a cutoff of 7.5 mcg/L is often used for modern assays.

• The stimulation tests are performed after an overnight fast. Serum samples are collected at intervals to capture the peak GH level.

• Two different stimuli should be used for most patients.
• In a patient with other pituitary hormone defects or a genetic defect, one test is sufficient to establish the diagnosis.
• Pharmacologic stimuli include clonidine, glucagon, arginine, and insulin-induced hypoglycemia:

The interpretation of the test results depends upon age and sex hormone concentrations.Children with constitutional delay of growth and puberty may have low GH results on provocative testing in the absence of true GHD (ie, false-positive results). Administration of sex steroids for a few days prior to the provocative GH testing reduces the chance of a false-positive result, as discussed below.