IGF-1

When should I do the IGF-1 Test?

This test is administered in various scenarios, including:

1. When a child exhibits delayed growth, short stature, and delayed puberty.
2. When an adult displays diminished bone density, decreased muscle strength, and elevated lipid levels, indicating potential inadequacies in GH and IGF-1 production.
3. In the presence of signs and symptoms suggesting gigantism in children or acromegaly in adults.
4. Throughout and following treatment for GH-related disorders.
5. When there are suspicions of a pituitary disorder.

What does the IGF-1 Test show?

Insulin-like growth factor-1 (IGF-1) is a hormone that collaborates with growth hormone (GH) to facilitate normal bone and tissue growth and overall development. The test measures the concentration of IGF-1 in the bloodstream.

IGF-1 is predominantly generated in the liver, skeletal muscles, and various other tissues when stimulated by GH. It serves as a pivotal mediator of GH's functions, promoting the growth of bones and various tissues while enhancing the production of lean muscle mass. IGF-1 also contributes to non-growth functions, such as regulating glucose and lipid metabolism, and has been associated with metabolic syndrome.

Given that GH is released into the bloodstream intermittently throughout the day, interpreting results from a single GH test can be challenging. IGF-1, on the other hand, mirrors both excesses and deficiencies in GH levels, and unlike GH, its concentration remains relatively stable throughout the day. This stability makes IGF-1 a valuable indicator of average GH levels. Consequently, the IGF-1 test is frequently utilized to assist in the evaluation of GH deficiency or excess.

How is the test used?

IGF-1 testing is typically requested in conjunction with a GH stimulation test under the following circumstances:

1. Children displaying symptoms suggest GH deficiency, such as slowed growth rate and short stature.
2. Adults presenting with symptoms that raise suspicion of GH deficiency, including decreased bone density, fatigue, adverse lipid profile changes, and reduced exercise tolerance. However, it's important to note that routine IGF-1 testing for adults with these symptoms is uncommon, as GH and IGF-1 deficiencies are exceedingly rare underlying causes.
3. When there are concerns about an underactive pituitary gland, and periodically as part of monitoring for individuals undergoing GH therapy.

Less frequently, IGF-1 testing may be coupled with a GH suppression test in the following scenarios:

1. When a child exhibits signs of gigantism.
2. When an adult displays indications of acromegaly.

After the surgical removal of a GH-producing pituitary tumor, GH and IGF-1 tests are ordered to assess whether the tumor has been completely excised. Furthermore, IGF-1 testing is regularly scheduled during drug and/or radiation therapy that typically follows tumor surgery. Over several years, periodic IGF-1 level assessments help monitor GH production and watch for potential pituitary tumor recurrence.

What does the result show?

Interpreting a normal IGF-1 level requires careful consideration within its context. It's important to note that some individuals with a GH deficiency may still exhibit a normal IGF-1 level.

When the IGF-1 level is diminished, it often indicates the presence of a GH deficiency or a reduced sensitivity to GH. In the case of children, GH deficiency may have already resulted in short stature and delayed development, and treatment may involve GH supplementation. GH deficiency occurring from birth can be attributed to genetic mutations or brain defects/trauma. In adults, while there is a natural age-related decline in GH production, lower-than-expected levels may still suggest the presence of a GH deficiency or diminished responsiveness to GH.

Elevated levels of IGF-1 typically signify an uptick in GH production. It's important to note that GH levels fluctuate throughout the day, so IGF-1 levels reflect the average GH production rather than the precise GH concentration in the blood at the time of the IGF-1 measurement. This remains accurate until the liver's capacity to generate IGF-1 is saturated. In cases of markedly heightened GH production, the IGF-1 level will plateau at a consistently elevated maximum level. Elevated levels of both IGF-1 and GH may serve as indicators of acromegaly in adults.

What are the typical signs and symptoms associated with a deficiency in GH and IGF-1?

In children, the presence of the following signs and symptoms may suggest a deficiency in GH and/or IGF-1:

1. Slower growth rate during early childhood compared to peers.
2. Shorter stature, both in terms of arm and leg lengths, as well as lower weight when compared to children of the same age.
3. Delayed onset of puberty.
4. X-ray results indicating delayed bone development.
5. Thin hair.
6. Poor nail growth.
7. Delayed closure of the skull's sutures.

In adults, notably low levels of GH and/or IGF-1 may manifest as subtle and nonspecific symptoms including:

1. Decreased bone density.
2. Fatigue.
3. Adverse changes in lipid profiles.
4. Reduced capacity for exercise.
5. Experiencing depression.
6. Thinning and dryness of the skin

What are the signs and symptoms associated with an excess production of GH and IGF-1?

The signs and symptoms of excess GH and IGF-1 production can vary between children and adults:

In children, the primary indicator is notably tall stature. Other manifestations of gigantism in children may encompass:

1. Mild to moderate obesity.
2. An oversized head.
3. Excessive growth of hands and feet.

In adults, the signs and symptoms are often more subtle and may include:

1. A larger nose, thicker lips, a more pronounced jaw, or finger thickening, leading to ill-fitting rings and shoes.
2. A deepened, husky voice.
3. Enlargement of various organs (liver, heart, kidneys, spleen, thyroid/parathyroid glands, pancreas).
4. An enlarged tongue.
5. Erectile dysfunction.
6. Fatigue.
7. Headaches and disturbances in vision.
8. Joint pain and swelling.
9. Irregularities in the menstrual cycle (in females).
10. Muscle weakness.
11. Snoring.
12. Increased size and activity of sebaceous and sweat glands, resulting in excessive sweating and body odor.
13. Thickening of the skin, the presence of skin tags, and increased coarse body hair.
14. Peripheral neuropathy, such as carpal tunnel syndrome.