IGF-1, which is short for insulin-like growth factor 1, is a hormone that's made by your liver. While it's especially known for its role in helping kids grow taller, the natural growth hormone also has many health implications once we reach adulthood.
“Optimal IGF-1 levels can help support energy, muscle mass, recovery after exercise, cognition, mood, and skin,” says Lifeforce Physician Kimberly Hartzfeld, DO, OB-GYN.
As we age, our IGF-1 levels start to decline; however, that's not necessarily a bad thing. When it comes to IGF-1, we don't want our levels to spike too high or dip too low. Here's everything you need to know about IGF-1, and how to optimize your levels.
What Is IGF-1?
Insulin-like growth factor (or IGF-1) is a hormone present in our blood. It's called "insulin-like" because its molecular structure is very similar to the hormone insulin. Like insulin, IGF-1 also exhibits blood sugar-lowering effects, although IGF-1 is not nearly as effective at decreasing blood glucose levels as insulin is, according to a 2004 report in the Journal of Clinical Investigation.
IGF-1 is produced in response to human growth hormone (HGH) being released by the pituitary gland. Normally, the pituitary gland releases HGH throughout the day, but HGH production is especially stimulated by sleep, stress, exercise, low blood sugar levels, and taking in amino acids (from protein), according to the Cleveland Clinic.
Both IGF-1 and HGH are responsible for helping our bodies grow during childhood and adolescence — that's why kids with IGF-1 deficiency or insensitivity may be prescribed an injected medicine that contains manufactured HGH to help them grow, according to the U.S. National Library of Medicine. But IGF-1 also plays an important role once we reach adulthood: The hormone helps regulate our metabolism and helps us build and maintain lean muscle mass, among others.
Why Does IGF-1 Decrease As We Age?
It is well-documented that both growth hormone and insulin-like hormone-1 decline with age, as many things do, and the causes are multifactorial. "Some of this is related to changes in sleep, stress, physical activity levels, body composition, and nutrition, which are common [things that change] as people age," says Renae Thomas, MD, MPH, a Lifeforce Physician.
"After our 30th birthday, growth hormone secretion declines by about 15% per decade. Our levels of IGF-1, which mediates many of the effects of growth hormone, also decline with age," Dr. Thomas says.
There are many reasons to try and optimize growth hormone and IGF-1 levels as we age, including helping to sustain lean muscle mass while preventing belly fat, maintaining healthy bone mineral density, and supporting heart and brain health.
"The top responses I hear from patients when we optimize their IGF-1 levels is improved energy, sleep, mood, and body composition," Dr. Thomas says.
However, it is important to note that you want to hit the sweet spot with growth hormone and get your IGF-1 levels in the optimal range, which Dr. Thomas says is typically top 25% of your age-corrected range. For example, if your normal range is 50 to 200 ng/mL, your optimal range is 162 to 200 ng/mL.
Normal IGF-1 Levels By Age
According to Labcorp, these are the normal IGF-1 level ranges according to age:
The IGF-1 Level Sweet Spot
When it comes to IGF-1 levels, there's a sweet spot. "While you may not feel your best with low levels, you don’t want too much either, as excess growth hormone can be associated with excessive growth (including that of potential tumors), diabetes, cardiovascular disease, and accelerated aging," Dr. Thomas says.
In fact, an August 2021 analysis of more than 400,000 people in the journal Aging Cell observed that people with high IGF-1 levels were at a greater risk of premature death and disease. However, it's worth noting that this study was observational and does not prove cause and effect. "In those with higher IGF-1 [coupled with] poorer health outcomes, this raises the question of what comes first, the elevated IGF-1 level, or a disease state-causing IGF to elevate via a different mechanism," Dr. Thomas says.
"When it comes to IGF-1, I often see higher levels in those who sleep well and exercise regularly, but in contrast, I also see IGF-1 elevations associated with some medical conditions, including PCOS, insulin resistance, and cancer," Dr. Thomas says. "As conditions such as insulin resistance and cancer also typically increase with advancing age, it makes sense that elevated IGF levels in older age, may not be reflective of good health, as opposed to a higher IGF-1 in a younger person due to their health-promoting lifestyle behaviors."
The researchers of the Aging Cell study highlight that the link between IGF-1 and health risks is U-shaped, implying that both high and low levels of IGF-1 may indicate unfavorable health outcomes. This may suggest that you want IGF-1 in the optimal range — not too high or low, Dr. Thomas says, adding that your Lifeforce Physician can discuss this and tailor a treatment approach specifically for you.
How to Optimize Your IGF-1 Levels
Many healthy habits that you already focus on daily are actually linked to improving IGF-1 levels naturally. Sticking to the basics, like optimizing your diet and sleep habits, can support your whole-body health whether or not your goal is to boost your IGF-1 levels.
Here are some tried-and-true tips for optimizing your IGF-1 levels and overall health:
1. Eat Enough Protein Every Day
Some systematic reviews show that a higher protein intake is associated with increased IGF-1 levels. Again, you want to aim for optimal levels — more isn’t always better! — as high animal protein intake stimulating very high IGF-1 levels has also been associated with increased risk for cancer and premature mortality.
"I think we still need more research here as to what is optimal," Dr. Thomas says. "I typically recommend meeting protein requirements (many people fall short of this, especially as they age), choosing mostly plant-based sources of protein (these tend to not have the same associations with cancer and mortality), and not going overboard with protein (the goal is optimal, not excess!)."
For people who work out and are trying to build or maintain lean muscle, the general consensus is to aim for up to 0.7 grams of protein per pound of body weight, per a 2018 report in the British Journal of Sports Medicine.
2. Get Good Sleep
Sleep deprivation tends to suppress IGF-1 levels, and sleep quality also tends to decline with age. "Suboptimal sleep impacts endocrine (hormone) secretion and increases cortisol (stress hormone) release in the evening, and these can lead to decreases in concentrations of both growth hormone and IGF-1," Dr. Thomas says.
This is at least in part because growth hormone is mostly released during slow-wave or deep sleep. Dr. Thomas recommends sleeping for seven to nine hours and aiming for at least 60 minutes of deep sleep, as well as treating any insomnia and/or sleep apnea to help optimize your IGF-1 and growth hormone levels.
3. Exercise Regularly
Exercise of any kind (type, duration, or intensity) tends to be associated with increased basal levels of testosterone, IGF-1, and HGH in both males and females over 40 years of age compared to those who do not exercise regularly, according to a 2022 systematic review in Sports Medicine.
"Leg exercises, where large muscle groups are recruited and require the most effort, stimulate the highest release of these hormones," Dr. Thomas says. (Want healthy hormones? Read our article on key strength training techniques here.)
Curious about your IGF-1 levels, or your hormone balance overall? The Lifeforce Membership includes an at-home blood test measuring 40+ biomarkers including a full hormone panel, critical nutrients, and more. Get started with $200 off today.
This article was medically reviewed by Renae Thomas, MD, MPH; ABFM Board Certified in Family Medicine, ABPM Board Certified in Public Health, & General Preventive Medicine; ABLM Board Certified in Lifestyle Medicine.
