and to evaluate pituitary function. It is not diagnostic of GH



deficiency but may be ordered along with GH stimulation tests to offer

additional information. IGF-1 levels and the measurement of GH can also

provide information related to GH insensitivity.

IGF-1 may be ordered with other pituitary hormone tests, such as

adrenocorticotropic hormone (ACTH), to help diagnose hypopituitarism.

It may be used to monitor the effectiveness of treatment for growth

hormone deficiencies and growth hormone insensitivity.

IGF-1 testing and a GH suppression test can be used to detect a

GH-producing pituitary tumor. Its presence is then confirmed with

imaging scans that help identify and locate the tumor. If surgery is

necessary, GH and IGF-1 levels are measured after the tumor's removal

to determine whether or not all of it was successfully removed. Drug

and/or radiation therapy may be used in addition to (or sometimes

instead of) surgery to try to decrease GH production and return IGF-1

to normal or near normal concentrations. IGF-1 may be used to monitor

the effectiveness of this therapy at regular intervals for years

afterward to monitor GH production and to detect tumor recurrence.

When is it ordered?

IGF-1 testing may be ordered, along with a GH stimulation test, when a

child has symptoms of GH deficiency, such as a slowed growth rate and

short stature. They also may be ordered when adults have symptoms that

the doctor suspects may be due to a GH deficiency. An IGF-1 also may be

ordered when a doctor suspects that a person has an underactive

pituitary gland and at intervals to monitor patients on GH therapy.

IGF-1 testing may be ordered, along with a GH suppression test, when a

child has symptoms of gigantism, an adult shows signs of acromegaly,

and/or when a doctor suspects that a patient has hyperpituitarism.

When a GH-producing pituitary tumor is found, GH and IGF-1 are ordered

after the tumor is surgically removed to determine whether all of the

tumor has been extracted. IGF-1 also is ordered at regular intervals

when a patient is undergoing the drug and/or radiation therapy that

frequently follow tumor surgery.

IGF-1 levels may be ordered at regular intervals for many years to

monitor a patient's GH production and to watch for pituitary tumor

recurrence.

What does the test result mean?

NOTE: This test has no single number that identifies an abnormal

result. Your lab report (see a sample report) should include a range of

numbers (reference range) that identifies what is expected for you

based on your age, sex, and the method used in that laboratory. You can

find more information about expected results at Reference Ranges and

What They Mean. Lab Tests Online strongly recommends that you discuss

the meaning of your test results with your doctor.

Normal concentrations of IGF-1 must be considered in context. Some

patients can have a GH deficiency and still have a normal IGF-1

concentration.

Decreased IGF-1

If IGF-1 concentrations are decreased, then it is likely that there is

a deficiency of GH (GH Deficiency; GHD) or an insensitivity to GH. If

this is in a child, the GH deficiency may have already caused short

stature and delayed development and may be treated with GH

supplementation. Adults will have an age-related decrease in

production, but lower than expected concentrations may reflect a GH

deficiency or insensitivity.

If a decrease in IGF-1 is due to a more general decrease in pituitary

function (hypopituitarism), then several of the patient's pituitary

hormones will need to be evaluated and may be supplemented to bring

them up to normal levels. Reduced pituitary function may be due to

inherited defects or can rise as a result of pituitary damage following

conditions such as trauma, infections, and inflammation.

Decreased levels of IGF-1 also may be seen with nutritional

deficiencies (including anorexia nervosa), chronic kidney or liver

disease, inactive/ineffective forms of GH, and with high doses of

estrogen.

Increased IGF-1

Elevated levels of IGF-1 usually indicate an increased production of

GH. Since GH levels vary throughout the day, IGF-1 concentrations are a

reflection of average GH production, not of the actual amount of GH in

the blood. This is accurate up to the point at which the liver's

capacity to produce IGF-1 is reached. With severely increased GH

production, IGF-1 levels will stabilize at an elevated maximum

concentration.

Increased concentrations of GH and IGF-1 are normal during puberty and

pregnancy but otherwise are most frequently due to pituitary tumors

(usually benign). If other pituitary hormones are also abnormal, then

the patient may have a condition causing general hyperpituitarism.

If IGF-1 is still elevated after the surgical removal of a pituitary

tumor, then the surgery may not have been fully effective. Decreasing

IGF-1 concentrations during subsequent drug and/or radiation therapies

indicate that the treatment is lowering GH production. If levels of

IGF-1 become ?normalized,? then the patient is no longer producing

excess amounts of GH. When a patient is undergoing long term

monitoring, an increase in IGF-1 levels may indicate a recurrence of

the pituitary tumor.

Is there anything else I should know?

If an IGF-1 level is normal and the doctor still strongly suspects a GH

deficiency, then he may order another test, an IGF BP 2 or IGF BP 3

(insulin-like growth factor binding protein 2 or 3), to help confirm

the GH deficiency.