Growth Hormone, Stimulation and Suppression Tests


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Related to Growth Hormone, Stimulation and Suppression Tests: Growth hormone deficiency

Growth Hormone, Stimulation and Suppression Tests

Synonym/acronym: Somatotropic hormone, somatotropin, GH, hGH.

Common use

To assess pituitary function and evaluate the amount of secreted growth hormone to assist in diagnosing diseases such as giantism and dwarfism.

Specimen

Serum (1 mL) collected in a gold-, red-, or red/gray-top tube.

Normal findings

(Method: Immunoassay) Growth Hormone
AgeConventional UnitsSI Units (Conventional Units × 1)
Cord blood8–40 ng/mL8–40 mcg/L
1 day5–50 ng/mL5–50 mcg/L
1 wk5–25 ng/mL5–25 mcg/L
Child2–10 ng/mL2–10 mcg/L
Adult
 Male0–5 ng/mL0–5 mcg/L
 Female0–10 ng/mL0–10 mcg/L
 Male older than 60 yr0–10 ng/mL0–10 mcg/L
 Female older than 60 yr0–14 ng/mL0–14 mcg/L
Stimulation Tests
Rise above baselineGreater than 5 ng/mLGreater than 5 mcg/L
Peak responseGreater than 10 ng/mLGreater than 10 mcg/L
Suppression Tests0–2 ng/mL0–2 mcg/L

Description

Human growth hormone (GH) is secreted in episodic bursts by the anterior pituitary gland; the highest level is usually secreted during deep sleep. Release of GH is modulated by three hypothalamic factors: GH-releasing hormone, GH-releasing peptide-6, and GH inhibitory hormone (also known as somatostatin). The effects of GH are carried out by insulin-like growth factors, formerly called somatomedins. GH plays an integral role in growth from birth to puberty. GH promotes skeletal growth by stimulating hepatic production of proteins; it also affects lipid and glucose metabolism. Random levels are rarely useful because secretion of GH is episodic and pulsatile. Stimulation tests with arginine, glucagon, insulin, or l-dopa, as well as suppression tests with glucose, provide useful information.

This procedure is contraindicated for

    N/A

Indications

  • Assist in the diagnosis of acromegaly in adults
  • Assist in establishing a diagnosis of dwarfism or growth retardation in children with decreased GH levels, indicative of a pituitary cause
  • Assist in establishing a diagnosis of gigantism in children with GH increased levels, indicative of a pituitary cause
  • Detect suspected disorder associated with decreased GH
  • Monitor response to treatment of growth retardation

Potential diagnosis

Increased in

  • Production of GH is modulated by numerous factors, including stress, exercise, sleep, nutrition, and res-ponse to circulating levels of GH.

  • Acromegaly
  • Anorexia nervosa
  • Cirrhosis
  • Diabetes (uncontrolled)
  • Ectopic GH secretion (neoplasms of stomach, lung)
  • Exercise
  • Gigantism (pituitary)
  • Hyperpituitarism
  • Laron dwarfism
  • Malnutrition
  • Renal failure
  • Stress

Decreased in

    Adrenocortical hyperfunction (inhibits secretion of GH) Dwarfism (pituitary) (related to GH deficiency) Hypopituitarism (related to lack of production)

Critical findings

    N/A

Interfering factors

  • Drugs that may increase GH levels include alanine, anabolic steroids, angiotensin II, apomorphine, arginine, clonidine, corticotropin, cyclic AMP, desipramine, dexamethasone, dopamine, fenfluramine, galanin, glucagon, GH-releasing hormone, hydrazine, levodopa, methamphetamine, methyldopa, metoclopramide, midazolam, niacin, oral contraceptives, phenytoin, propranolol, and vasopressin.
  • Drugs that may decrease GH levels include corticosteroids, corticotropin, hydrocortisone, octreotide, and pirenzepine.
  • Failure to follow dietary and activity restrictions before the procedure may cause the procedure to be canceled or repeated.

Nursing Implications and Procedure

Pretest

  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching:   Inform the patient this test can assist in assessing the amount of GH secreted.
  • Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
  • Obtain a history of the patient’s endocrine system, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Record pertinent information related to diet, sleep pattern, and activity at the time of the test.
  • Note any recent procedures that can interfere with test results.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values).
  • Review the procedure with the patient. Protocols may vary depending on the type of induction used. Patients may be allowed to walk around, or they may be required to be recumbent. Inform the patient that multiple specimens may be required. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
  • Sensitivity to social and cultural issues,  as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Note that the patient should fast and avoid strenuous exercise for 12 hr before specimen collection. Protocols may vary among facilities.

Intratest

  • Potential complications: N/A
  • Ensure that the patient has complied with dietary and activity restrictions; ensure that food and strenuous activity have been restricted for at least 12 hr prior to the procedure.
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture. Test samples may be requested at baseline and 30-, 60-, 90-, and 120-min intervals after stimulation and at baseline and 60- and 120-min intervals after suppression.
  • Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
  • Promptly transport the specimen to the laboratory for processing and analysis.

Post-Test

  • Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
  • Instruct the patient to resume usual diet, fluids, medications, and activity, as directed by the HCP.
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

  • Related tests include ACTH and insulin.
  • Refer to the Endocrine System table at the end of the book for related tests by body system.
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