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Growth Hormone 

  • Author: Muhammad Bader Hammami, MD; Chief Editor: Eric B Staros, MD  more...
 
Updated: Jun 07, 2013
 

Reference Range

Random growth hormone (GH) levels in a healthy person range as follows:

  • Men: < 5 ng/mL or < 226 pmol/L
  • Women: < 10 ng/mL or < 452 pmol/L
  • Children: 0-20 ng/mL or 0-904 pmol/L
  • Newborns: 5-40 ng/mL or 226-1808 pmol/L

GH suppression test value (using 100 g glucose) in a healthy person is as follows:

  • < 0-2 ng/mL or 0-90 pmol/L or undetectable

GH stimulation test values (using arginine, glucagon, or insulin) are as follows:

  • Normal peak value: >10 ng/mL or >452 pmol/L
  • Intermediate peak value: >5 ng/mL or >226 pmol/L
  • Subnormal peak value: < 5 ng/mL

SI Units = Conventional Units X 1 (mcg/L = ng/mL X 1)

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Interpretation

High growth hormone (GH) levels associated with high insulinlike growth factor 1 (IGF-1) levels and normal GH and IGF-1 receptors cause gigantism in children or acromegaly in adults, and it is seen in the following conditions:

  • Pituitary gland tumor (mostly, benign adenoma)
  • Multiple endocrine neoplasia type I (MEN-I)
  • Nonpituitary gland tumor: Some tumors located in the lungs, adrenal glands, pancreas, or elsewhere can secrete either GH or GH-releasing hormone (GHRH), and the later can stimulate the production of GH by the pituitary gland
  • McCune-Albright syndrome: An early postzygotic genetic disease due to activating mutations in the alpha subunit of G protein (s subtype) that can cause constitutional activation of the post-GHRH receptor pathway and increase GH production from the pituitary gland

High GH levels not associated with high IGF-1 levels are seen in the following conditions:

  • Uncontrolled diabetes mellitus
  • Kidney disease
  • Starvation
  • Inherited resistance to GH (Laron syndrome)

High GH levels associated with high IGF-1 levels are seen in the following condition:

  • Dwarfism due to IGF-1 resistance because of inactivating mutations in the IGF-1 receptor

Low levels of GH associated with low IGF-1 levels causes dwarfism in children and vague, nonspecific symptoms (fatigue, decreased muscle mass, osteoporosis) and increased risk of cardiovascular diseases in adults, and it is seen in the following condition:

  • Hypopituitarism, which could be due to damage to the pituitary gland or the hypothalamus, which controls the pituitary gland; this damage could be due to a tumor, trauma, infection, surgery, radiation used to treat the tumor, or problems with the blood supply to the pituitary gland
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Collection and Panels

The patient should not exercise or eat anything for 10 hours before the test (unless specifically instructed to do so for some of the dynamic tests); water is permitted. He or she may be asked to sit quietly for 30 minutes right before the test.[1]

Certain medicines can affect growth hormone (GH) test results, such as corticosteroids and estrogen (including birth control pills). The patient may be asked to stop taking these medicines before the test.[2]

Drugs that can increase GH levels include the following[2] :

  • Amphetamines
  • Dopamine
  • Estrogens
  • Histamine
  • Nicotinic acid
  • Arginine
  • Glucagon
  • Insulin

Drugs that can decrease GH levels include the following[2] :

  • Corticosteroids
  • Phenothiazines

To prepare the specimen, usually 5 mL of blood serum is collected by venipuncture and drawn in a red top container.[1]

Related tests are as follows[1, 2] :

  • GH suppression tests
  • GH stimulation tests
  • Insulinlike growth factor 1 (IGF-1) tests
  • GH-releasing hormone (GHRH) tests
  • Cortisol tests
  • Corticotropin tests
  • Thyroid-stimulating hormone (TSH) tests
  • Prolactin tests
  • Luteinizing hormone (LH)/follicle-stimulating hormone (FSH) tests
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Background

Description [1, 2, 3]

Note the image below.

Growth hormone. Growth hormone.

Growth hormone (GH) or somatotropin is produced and released by specialized cells (somatotrophs) in the anterior part of the pituitary gland. GH is needed for growth and has important effects on protein, lipids, and carbohydrate metabolism, which are accomplished directly as a result of GH binding to its receptor on target cells or indirectly primarily through insulinlike growth factor 1 (IGF-1), a hormone secreted from the liver and other tissues in response to GH. The majority of the growth-promoting effects of GH are through IGF-1 acting on its target cells.

GH release in the pituitary is primarily determined by the balance of 2 antagonistic regulatory hormones secreted from the neurosecretory nuclei of the hypothalamus. These are GH-releasing hormone (GHRH), or somatocrinin, which is stimulatory, and GH-inhibiting hormone (GHIH), or somatostatin, which is inhibitory. These 2 hypothalamic hormones, in turn, are modulated by many factors, including stress, exercise, nutrition, sleep, IGF-1, and GH itself (negative feedback loop).

Integration of all the factors that affect GH synthesis and secretion leads to a pulsatile pattern of release. The largest and most predictable GH peak occurs about an hour after the onset of deep sleep.

Indications/applications [1, 2, 4]

The following conditions suggest the possible need for GH testing:

  • Signs or symptoms of GH excess: Acromegaly in adults (eg, soft tissue swelling and enlargement of extremities, coarsening of facial features, prognathism, macroglossia) and gigantism in children
  • Signs or symptoms of GH deficiency: Short stature in children (the child is significantly shorter than others of the same age) and changes in muscle mass, cholesterol levels, and bone strength in adults
  • History of a pituitary gland problem (eg, trauma, surgery, radiation)
  • Adult with signs or symptoms suggestive of a deficiency in other pituitary hormones (eg, thyroid, adrenal, gonads)
  • Follow-up for other abnormal hormone test results
  • Monitor treatment in patients on GH replacement therapy
  • Assess the success of therapy for acromegaly or gigantism
  • Children who have had radiation treatment of the central nervous system or whole body irradiation (eg, treatment for malignancy, prior to stem cell transplantation)

Considerations/precautions

GH levels in blood change during the day and are affected by exercise, sleep, emotional stress, and diet.[1, 2]

GH is released in pulses. A higher level may be normal if the blood was drawn during a pulse. A lower level may be normal if the blood was drawn around the end of a pulse. Because of this, random GH levels are generally not very useful. Too much overlap occurs between abnormal GH results and normal daily variations. It is more useful to perform GH stimulation tests (if one suspects deficiency) and GH suppression tests (if one suspects excess) and to correlate GH levels with IGF-1 levels, as IGF-1 levels integrate GH excesses and deficiencies and are stable throughout the day.[1, 2]

For the GH stimulation test, a sample of blood is drawn after 10-12 hours of fasting. Then, under close medical supervision, a person is given an intravenous solution of insulin or arginine (or other stimulus). Blood samples are then drawn at timed intervals, and GH levels are tested in each sample to see if the pituitary gland was stimulated to produce the expected levels of GH. If GH levels are not adequately stimulated during a GH stimulation test (usually on at least two tests) and the person has symptoms of GH deficiency and a low IGF-1 level, then a GH deficiency is likely.[1, 2]

For the GH suppression test, a sample of blood is drawn after 10-12 hours of fasting. A person is then given a standard glucose solution to drink. Blood samples are drawn at timed intervals, and GH levels are tested. If a person's GH levels are not adequately suppressed during a GH suppression test and the person has symptoms of gigantism or acromegaly and a high IGF-1 level, then it is likely that he or she is producing too much GH. If a mass shows up on a CT scan or MRI of the pituitary, then a pituitary tumor (usually benign) is likely present.[1, 2]

If the person may have hypothyroidism, then GH testing for GH deficiency should not be performed until his or her thyroid function has been evaluated and treated, as thyroid deficiencies can cause symptoms similar to GH deficiency.[1, 2]

GH abnormalities can usually be treated once the causes are identified, but to have a good outcome, they should be identified as soon as possible because some changes are not reversible.[3]

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Contributor Information and Disclosures
Author

Muhammad Bader Hammami, MD Resident Physician, Department of Internal Medicine, St Louis University School of Medicine

Disclosure: Nothing to disclose.

Chief Editor

Eric B Staros, MD Associate Professor of Pathology, St Louis University School of Medicine; Director of Clinical Laboratories, Director of Cytopathology, Department of Pathology, St Louis University Hospital

Eric B Staros, MD is a member of the following medical societies: American Medical Association, American Society for Clinical Pathology, College of American Pathologists, Association for Molecular Pathology

Disclosure: Nothing to disclose.

References
  1. Fischbach FT, Dunning MB III, eds. Chemistry Studies. Manual of Laboratory and Diagnostic Tests. 8th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2009. Chapter 6.

  2. Pagana KD, Pagana TJ, eds. Blood Studies. Mosby’s Manual of Diagnostic and Laboratory Tests. 4th ed. St. Louis, Mo: Mosby Elsevier; 2010. Chapter 2.

  3. Kasper DL, Braunwald E, Fauci AS, Hauser SL, Longo DL, Jameson JL, et al. Disorders of the Anterior Pituitary and Hypothalamus. Harrison’s Principles of Internal Medicine. 16th ed. New York, NY: McGraw-Hill; 2005. 2087.

  4. Daniels R, ed. Delmar's Guide to Laboratory and Diagnostic Tests. 2nd ed. Stamford, Conn: Delmar Cengage Learning; 2009.

 
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