Specimen

Serum or Plasma

Collection Medium:

Alternate
Collection Media:

Light Green top tube (Lithium Heparin), Green top tube (Na Heparin), 
Lavender top tube (EDTA), Pink top tube (EDTA sprayed)

Minimum:

Adult recommended minimum:   1.0 ml serum or plasma
Adult absolute minimum:      0.4 ml serum or plasma
Pediatric absolute minimum:  0.4 ml serum or plasma

If additional tests are going to be ordered, extra red top tubes may be 
needed.  Please call the lab for consultation.

Analytic Time:

4 working days

Reference Range:

Male:
  0-6 years:           0.10-8.80 ng/mL
  7-17 years:          0.03-14.90 ng/mL
  18 years and older:  0.01-1.00 ng/mL

Female:
  0-6 years:           0.10-8.80 ng/mL
  7-17 years:          0.06-23.80 ng/mL
  18 years and older:  0.03-10.00 ng/mL

Test
Limitations:

Human growth hormone (GH, hGH, Somatotropin) is composed of a single 
polypeptide chain of 191 amino acids and is structurally similar to 
prolactin and placental lactogen. GH is produced in and released from 
the acidophilic cells of the anterior pituitary gland. Basal levels of 
GH in normal individuals are usually less than 2 ng/mL and are stable 
throughout the day. Normal elevations in GH occur following meals, 
after exercise, and during sleep.

Children who fail to grow at the expected rate and who have short 
stature with apparent normal body proportions often have a diminished 
capacity to secrete growth hormone. If the child may be short because 
of growth hormone deficiency, insulin-like growth factor-1 (IGF-1) and 
insulin-like growth factor binding protein-3 (IGFBP-3) should be the 
first screening tests. When growth hormone deficiency is marked, the 
diagnosis is relatively easy to confirm, as affected children present 
with severe growth failure, delayed bone age, and very low serum 
concentrations of growth hormone, IGF-1, and IGFBP-3. These children 
may have an isolated trophic hormone deficiency. The diminished 
capacity to secrete hGH may also result from a hypothalamic or 
hypophyseal lesion involving more than one releasing factor or trophic 
hormone. The deficiency may be either congenital or acquired. Children 
who have hypothyroidism may fail to have normal growth hormone release; 
therefore, growth hormone testing should be done only after a euthyroid 
state is induced by appropriate treatment.

Growth hormone deficiency in both adults and children may be the direct 
result of neoplastic or infiltrative disease of the pituitary. It may 
also follow cranial irradiation for brain tumors and other neoplasms. 
In patients with intracranial lesions involving the hypothalamus or 
pituitary, growth hormone values may be useful in evaluating the extent 
or progression of such lesions. The demonstration of elevated and 
unsuppressible serum growth hormone levels following glucose 
administration helps to confirm the diagnosis in adults with signs and 
symptoms of acromegaly and more rarely in children or adolescents with 
gigantism. After a glucose tolerance test, GH should suppress to less 
than 2 ng/mL, but fails to do so in patients with acromegaly.

The following tests -- Arginine Infusion, Insulin Tolerance, Combined 
Arginine- Insulin Infusion, L-dopa, Glucagon, Clonidine Simulation (not 
considered a reliable test for adults), Sleep-Induced GH Secretion, and 
Exercise-Induced GH Secretion -- should induce a peak GH value greater 
than 7 ng/mL in children and greater than 5 ng/mL in adults; lower 
values suggest deficiency. However, a recent consensus conference 
recommended that a peak GH during insulin tolerance testing of less 
than 3 ng/mL for the diagnosis of GH deficiency in adults be consulted. 
For children, some experts consider values of 7-10 ng/mL equivocal and 
only peak values of greater than 10 ng/mL as truly normal.

For suppression testing, normal subjects have growth hormone 
concentrations of less than 1 ng/mL within two hours of ingestion of a 
75 or 100 gram glucose dose. Patients with acromegaly fail to show 
normal suppression.

Methodology:

Chemiluminescent Immunoassay

CPT Code:

83003