IGF-1 (insulin-like growth factor 1)

How IGF-1 fits with growth hormone

Your pituitary gland releases growth hormone in bursts, and the size of those bursts varies with the time of day, age, sex, diet and activity. A random growth hormone level can be high or low depending on when the needle went in.

When growth hormone reaches the liver, it prompts the liver to make IGF-1, which then does much of the actual work of building bone and tissue. IGF-1 levels are much steadier, so they give a more reliable read on overall growth hormone activity.

When it is tested

• Suspected growth hormone excess (acromegaly in adults), where a high IGF-1 is usually the first clue and is then confirmed with a glucose suppression test.
• Monitoring treatment of acromegaly, where returning IGF-1 to normal is a key goal.
• Suspected growth hormone deficiency, often alongside stimulation testing.
• Monitoring people on therapies that act on the growth hormone system.

Why age-matched ranges matter

IGF-1 rises through childhood, peaks around puberty and declines across adult life. A value that would be normal at 30 can look high at 65, and a level that is typical at 65 would look low at 25. Always compare your number with the range for your age and sex on your lab report.

Labs differ in method and range, and illness or poor nutrition can affect hormone results, so a single low value is not automatically a growth hormone problem. It is interpreted with symptoms and other tests.

IGF-1 and midlife treatments

Interest in IGF-1 has grown alongside therapies such as sermorelin, a compounded GHRH analog intended to prompt the pituitary to release more of its own growth hormone. Clinicians may check IGF-1 before and during such treatment. Compounded sermorelin is not FDA-approved, and evidence for anti-aging benefits in healthy adults is limited.

Higher is not automatically better. Persistently elevated IGF-1, as in acromegaly, is associated with blood sugar, blood pressure and heart problems, which is part of why clinicians monitor it rather than chase a maximum.

Reading your own result

When you look at an IGF-1 report, find the reference range printed beside your value and check that it is specific to your age band. Many labs also report a standard deviation score, which shows how far you sit from the average for your age. Bring prior results to your visit, because a change over time often says more than any single number.