• Synonym
• Tubes
• Info
• Clinical
• Nl Result
• High Result
• Low Result

Synonym

• GH
• HGH
• Human growth hormone
• Somatotropin
• Somatotropic hormone

Tubes

• Red, tiger, or green top tube (or gel barrier tube)
• 4-6 mL of venous blood

Additional information

• Fasting and limited physical activity for 10-12 hours before the test
• Make sure the patient is relaxed and recumbent for 30 minutes before the test
• Handle sample gently to prevent hemolysis
• Reject lipemic samples
• Specimen must be refrigerated after collection as it is unstable at room temperature
• Send the sample to lab immediately

Info

• Growth hormone (GH) testing is a quantitative analysis of growth hormone levels in the blood
• GH is a polypeptide of 191 amino acids synthesized and secreted by somatotrophs/acidophils of the anterior pituitary gland
• Production of GH is controlled by many hormones and factors, which include:
• Growth hormone releasing hormone stimulates both synthesis and secretion of GH
• Somatostatin inhibits GH secretion
• Ghrelin (a preprohormone synthesized in the fundus of the stomach) stimulates secretion of GH
• Other factors such as stress, exercise, nutrition, sleep, hypoglycemia, glucagon, insulin, and vasopressin stimulate secretion of GH
• The function of GH and its effects in both elevated and diminished levels are listed in the Clinical section

Clinical

• The clinical utility of the Growth Hormone (GH) assay includes:
• Aids in the diagnosis of dwarfism or growth retardation which can result from pituitary or thyroid hypofunction
• Confirm diagnosis of gigantism in children
• Confirm diagnosis of acromegaly in adults
• Aids in the diagnosis of pituitary and hypothalamic tumors
• Evaluation and monitoring of the effecacy of GH therapy following surgery, chemotherapy, and/or radiotherapy for pituitary tumor
• GH affects many body tissues directly (binding to receptors on target cells such as adipocytes) and indirectly (via insulin like growth factor-1/IGF-1)
• The effects of GH include:
• Increases height by stimulating multiplication and division of chondrocytes of cartilage and osteocytes, promoting growth
• Increases calcium retention, with bone strengthening and increased mineralization
• Increases muscle mass by stimulating new muscle cells growth
• Enhances utilization of fat by stimulating triglyceride breakdown and oxidation in adipocytes
• Stimulates protein anabolism in many tissues, reflected by increased amino acid uptake, increased protein synthesis, and decreased oxidation of proteins
• Suppresses the ability of insulin to stimulate uptake of glucose in peripheral tissues and enhance glucose synthesis in the liver
• Contributes in the maintenance and function of pancreatic islet cells
• Plays a role in fuel homeostasis
• Stimulates immune system functioning
• GH assay as part of a stimulation test (with arginine, glucagon, insulin, or L-dopa) or a suppression test (with glucose) may yield additional information
• GH deficiency may manifest clinically depending on the severity (total or partial deficiency):
• Children
• Usually are 2 standard deviations below the mean for height
• Growth velocity is below the 10-25th percentile, which reflects growth deceleration
• Increased subcutaneous fat, especially around the trunk
• The face is immature, prominent forehead, and depressed midfacial development
• Dentition is delayed
• Delayed onset of puberty
• Adults
• Cool hands & feet
• Depression
• Labile mood
• Poor venous access
• Reduced exercise tolerance
• Reduced lean body mass and increased weight, with body fat mass predominantly in the abdominal region
• Reduced muscle mass and strength
• Thin dry skin
• Excess GH may clinically manifest depending on the age group it affects and may present with:
• Typical facies of acromegaly
• Frontal bossing
• Thickening of the nose
• Macroglossia
• Prognathism
• Bitemporal hemianopsia to blindness
• Enlarged extremities with sausage-shaped fingers
• Hypertension
• Hyperthyroidism
• Mild hirsutism in women
• Oily skin with skin tags
• Weight gain

Additional information

• GH is secreted in episodic spikes during day and highest just after sleep
• GH levels are highest in fall, lowest in spring
• GH has a half-life of only 20-25 minutes
• Recently administration of radioisotopes interfere with test results
• Related laboratory tests include:
• Glucose
• Glucose tolerance test (GTT)
• Growth hormone releasing hormone (GHRH)
• Insulin like growth factor-1/Somatomedin C
• Prolactin
• Thyroid stimulating hormone (TSH)

Nl Result

Consult your laboratory for their normal ranges as these may vary somewhat from the ones listed below.

High Result

Conditions associated with elevated GH include:

• Acromegaly/Pituitary gigantism
• Ectopic GH secretion (neoplasms of stomach, lung)
• Pituitary or hypothalamic tumor such as adenoma
• Hyperpituitarism
• Acute illness
• Anorexia nervosa and malnutrition
• Cirrhosis
• Diabetes mellitus (uncontrolled)
• Renal failure
• Hemoconcentration
• Laron dwarfism (GH resistant)
• Physiological
• After meals with protein
• Exercise
• Exposure to heat or cold
• Hypoglycemia
• Sleep
• Starvation
• Stress
• Drugs and substances
• ACTH
• Amino acids such as alanine, galanin and arginine
• Amphetamines
• Anabolic steroids
• Angiotensin II
• Apomorphine
• Citalopram
• Clomipramine
• Clonidine
• Cyclic AMP
• Desipramine
• Dexamethasone
• Diazepam
• Dopamine
• Estrogens
• Fenfluramine
• Glucagon
• Growth hormone-releasing hormone
• Hydrazine
• Indomethacin
• Insulin
• Interferon
• Interleukin
• Levodopa
• Methamphetamine
• Methyldopa
• Metoclopramide
• Midazolam
• Niacin
• Oral contraceptives
• Phenytoin
• Propranolol
• Pyridostigmine
• Tumor necrosis factor
• Vasopressin

Low Result

Conditions associated with decreased GH include:

• Pituitary dwarfism
• Congenital
• Defective pituitary development leading to pituitary aplasia
• Empty sella syndrome
• Encepalocele
• Midline brain defects
• Panhypopituitarism
• Septo-optic dysplasia
• Genetic abnormalities, including autosomal-recessive, autosomal-dominant, or X-linked defects or a mutation or deletion in the growth hormone gene or in growth hormone-releasing hormone
• Acquire
• Cranial irradiation
• Hypoxic insult
• Infiltrative diseases including sarcoidosis, tuberculosis, histiocytosis X, hemochromatosis, and lymphocytic hypophysitis
• Sheehan syndrome
• Trauma
• Tumors of the hypothalamic-pituitary region as in Craniopharyngioma or metastases to the pituitary (especially breast cancer)
• Adrenocortical hyperfunction
• Obesity
• Drugs and substances
• Bromocriptine
• Chlorpromazine
• Corticotropin
• Glucocorticoids
• Glucose ingestion
• Hydrocortisone
• Medroxyprogesterone
• Methyldopa
• Octreotide
• Phenothiazines
• Pirenzepine
• Prednisone
• Probucol
• Propantheline
• Valproic acid

References

• Ahn CW et al. Effects of growth hormone on insulin resistance and atherosclerotic risk factors in obese type 2 diabetic patients with poor glycaemic control. Clin Endocrinol (Oxf). 2006 Apr;64(4):444-9.
• eMedicine from WebMD®. Acromegaly. [Homepage on the Internet] ©1996-2007. Last updated on June 12, 2007. Last accessed on July 24, 2007. Available at URL: http://www.emedicine.com/derm/topic593.htm
• eMedicine from WebMD®. Growth Hormone Deficiency. [Homepage on the Internet] ©1996-2007. Last updated on May 12, 2006. Last accessed on July 24, 2007. Available at URL: http://www.emedicine.com/med/topic930.htm
• LabTestsOnline®. Growth Hormone. [Homepage on the Internet]© 2001-2007. Last reviewed on May 30, 2005. Last accessed on July 24, 2007. Available at URL: http://www.labtestsonline.org/understanding/analytes/growth_hormone/test.html
• Spadoni E et al. Smith-Magenis syndrome and growth hormone deficiency. Eur j Pediatr. 2004 Jul;163(7):353-8. Epub 2004 May 8.
• UTMB Laboratory Survival Guide®. HUMAN GROWTH HORMONE, serum. [Homepage on the Internet]© 2007. Last reviewed in February, 2006. Last accessed on July 24, 2007. Available at URL: http://www.utmb.edu/lsg/LabSurvivalGuide/chem/HUMAN_GROWTH_HORMONE.html