Insulin Like Growth Factor 1


Insulin-Like Growth Factor-1


Also known as: Somatomedin C

The insulin-like growth factor-1 (IGF-1) test is an indirect measure of the average amount of growth hormone (GH). IGF-1 and GH are peptide hormones vital for normal bone and tissue growth and development. GH is produced by the pituitary gland, a grape-sized gland located at the base of the brain behind the bridge of your nose. IGF-1 is produced by the liver and to a lesser degree by skeletal muscles, primarily in response to GH stimulation.
Excess GH and IGF-1 can cause abnormal growth of the skeleton and other signs and symptoms characteristic of gigantism and acromegaly. Both conditions can lead to enlarged organs, such as the heart, and to other complications such as type 2 diabetes, increased cardiovascular disease risk, high blood pressure, arthritis, and a decreased life span.
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.

Its concentration is measured by means of analysis of a blood sample drawn from the vein in the arm.

Purpose of the test

To identify diseases caused by deficiencies and overproduction of growth hormone (GH), also to evaluate pituitary function. and to monitor the effectiveness of GH treatment.

This test is prescribed as part of an evaluation of pituitary function, when you have symptoms of slow growth, short stature, and delayed development or decreased bone density, reduced muscle strength, and increased lipids that suggest insufficient GH and IGF-1 production.   Also when you have symptoms of gigantism (in children) or acromegaly (in adults) that suggest excess GH and IGF-1 production.
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.

Reference range values

Units: mcg/L
1Y         55 – 327
2Y         51 – 303
3Y         49 – 289
4Y         49 – 283
5Y         50 – 286
6Y         52 – 297
7Y         57 – 316
8Y         64 – 345  
9Y         74 – 388
10Y       88 – 452
11Y      111 – 551
12Y      143 – 693
13Y      183 – 850
14Y      220 – 972
15Y      237 – 996
16Y      226 – 903
17Y      193 – 731
18Y      163 – 584
19Y      141 – 483
20Y      127 – 424
21-25Y  116 – 358
26-30Y  117 – 329
31-35Y  115 – 307
36-40Y  109 – 284
41-45Y  101 – 267
46-50Y    94 – 252
51-55Y    87 – 238
56-60Y    81 – 225
61-65Y    75 – 212
66-70Y    69 – 200
71-75Y    64 – 188
76-80Y    59 – 177
81-85Y    55 – 166
Tanner Stages              

I:     63 – 279

II:    75 – 420

III     94 – 765

IV:   192 – 861

V:    171 – 814

I:     49 – 342

II:    115 – 428

III    145 – 760

IV:   244 – 787

V:   143 – 859

Abnormal findings
Low  IGF-1 concentrations can appear due to  a deficiency of GH or an insensitivity to GH.
If a decrease in IGF-1 is due to a more general decrease in pituitary function (hypopituitarism), this may be due to inherited defects.
On the other hand, it can rise as a result of pituitary damage following conditions such as trauma, infections, and inflammation.
Low levels of IGF-1 also may be seen with nutritional deficiencies, chronic kidney or liver disease, inactive/ineffective forms of GH, and with high doses of estrogen.
High  IGF-1 concentrations can appear due to puberty and pregnancy but are most frequently due to pituitary tumors. If other pituitary hormones are also abnormal, then the patient may have hyperpituitarism.


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