IGF-1 (Insulin-like Growth Factor 1)

Insulin-like Growth Factor 1, also known as IGF-1, is used as a biomarker for blood levels of human growth hormone. The blood level of IGF-1 appears to fluctuate over 24 hours and is found to be related to growth hormone secretion, hunger, sleep and exercise.

It is a hormone produced by the liver and other tissues which affects growth-promoting activities and glucose metabolism. Because IGF-1 is related to the production and secretion of growth hormone (HGH), physicians may use this measurement to assess growth hormone status.

IGF-1, What is it?

IGF-1 is a hormone produced in our body that is structurally very similar to insulin. It has an important role in growth during childhood and in adulthood, continues to have anabolic effects. IGF-1 is the main mediator of the effects of growth hormone, which, most of us know, can benefit male physique drastically and also has anti-aging effects.

 

What is the Relationship Between IGF-1 and GH?

As stated previously, IGF-1 is the primary mediator of GH secretion. So what exactly does that mean? It all starts in an area of the brain called the hypothalamus. Whenever GH needs to be secreted (GH levels are typically highest during periods of fasting and sleep) the hypothalamus releases growth hormone-releasing hormone (GHRH). This GHRH then binds to receptors in another area of the brain called the anterior pituitary. The anterior pituitary then releases GH into the bloodstream. GH has several effects on the body including a glucose sparing effect- meaning that instead of the body utilizing glucose as a primary energy source, the body taps into adipose tissue, using stored fat as energy. In this regard, GH can significantly help to burn. However, this is not the only favorable action of GH. GH also has several anabolic growth effects. It increases the uptake of amino acids from the blood and increases protein synthesis in skeletal muscle tissue. This anabolism however, can be come problematic due to the fact that GH also targets bone cells and just about every other cell in the body.

Excessive GH use can lead to a condition called acromegaly, which is characterized by uncontrolled bone growth. The most noticeable feature of someone with acromegaly or HGH abuse is the development of a jagged/uncharacteristically large jawline. Some oncologist fear that increased IGF-1 may accelerate certain cancers, but studies on this subject are contradictory.


Where does IGF-1 come into play?

GH acts directly on the liver to produce IGF-1

This IGF-1 is then released into the blood stream to further stimulate the growth effects of GH. These two hormones work synergistically to promote cellular growth effects to the bone cells, muscle cells, nervous system cells, immune cells, and just about every cell in our body. GH also has a “diabetogenic effect”, meaning that when GH binds to receptors on the liver, the liver is instructed to break down glycogen into glucose, which fuels growth effects.

Other benefits and effects of IGF-1

Interestingly enough, elevated IGF-1 levels (from elevated GH levels) may potentially have a beneficial effect on erectile dysfunction [1]. In 2011 a paper titled “IGF-1 levels are significantly correlated with patient-reported measures of sexual function” Growth hormone (GH) supplementation may help to preserve erectile function. Researchers assessed whether serum insulin-like growth factor 1 (IGF-1) levels, a surrogate for GH levels, correlated with sexual function scores in 65 men who completed the Sexual Health Inventory for Men (SHIM) and Expanded Prostate Cancer Index Composite (EPIC) questionnaires, and had serum IGF-1 and testosterone levels determined. Median±s.d. IGF-1 level, SHIM and EPIC scores were 235.0±86.4, 19.5±8.7 and 56.4±28.3 mg ml−1, respectively. IGF-1 levels and total SHIM score correlate significantly (r=0.31, P=0.02), as do IGF-1 levels and all individual SHIM question scores, and IGF-1 levels and the sexual domain of the EPIC questionnaire (r=0.30, P=0.02)

The second figure below represents the total Sexual Health Inventory for Men (SHIM) score vs serum insulin-like growth factor (IGF-1) level. All subjects' IGF-1 levels plotted against their self-reported scores of sexual function based on total SHIM score. There is a statistically significant correlation between the two measured values, (Spearman's correlation coefficient, r=0.31; P=0.02).

Another study published titled “Men with high levels of anabolic hormones less likely to develop worsening frailty” Proved that having higher baseline levels of vitamin D, insulin-like growth factor-1 (IGF-1) and its binding protein 3 (IGFBP3) was associated with a lower risk of worse frailty status four years later [2]. "Vitamin D, besides maintaining bone health, regulates muscle function, and low vitamin D levels are linked to lower muscle mass and strength. IGF-1 affects muscle growth and repair, and its action and levels are modified by its carrier protein IGFBP3," Swiecicka said.
Also linked to a lower likelihood of frailty status worsening were higher baseline levels of the hormone dehydroepiandrosterone sulfate (DHEA-S), but only in the oldest men. Several potential pathways could link DHEA-S with frailty. Swiecicka said, "DHEA-S may have direct anabolic effect on muscle, and, more recently, its neuroprotective and immune system-modulating effects have been described."

Products that naturally raise IGF-1 levels

How might we safely raise GH and IGF-1 levels? There are two types of drugs that can safely raise GH and IGF-1 levels without greatly exceeding normal physiological levels (the higher we exceed normal physiological levels the greater the risk for unwanted pathology such as acromegaly and enlarged organs). These two types of drugs are:

1. Growth Hormone Secretagogues
2. Growth Hormone Releasing Hormone Mimetics

Growth Hormone Secretagogues (GHS)

GHSs are typically sequences of connected peptides (called Growth Hormone Releasing Peptides) that bind to the GHS receptor[3]. These receptors are present in many areas of the body, but of importance, in the hypothalamus and anterior pituitary, the areas responsible for GH release. The natural ligand to the GHS receptor in the body is ghrelin, the hormone responsible for sensing hunger and speeding up gastric emptying. This is why when GHRP-6 is administered subcutaneously, the patient will often report voracious hunger. This effect may be beneficial to those who have trouble consuming enough food to gain weight and muscle mass. Not only does this drug induce hunger but it causes a large but very shortly sustained release in GH. Typically this GH “spike” only lasts about 4 hours (GHRP-6 has a very short half-life in the body). This short duration disallows a proportional IGF-1 response from the liver. This problem was solved with the invention of Ibutamoren.

Ibutamoren is a non-peptidic compound (vs peptidic GHRPs) that binds to the GHS receptor.

Ibutamoren, as a ligand, acts directly on arcuate neurons of hypothalamus to stimulate the release of GHRH. Activation of these neurons by ibutamoren can be inhibited by sst (somatostatin) or pretreatment with GH (IGF-1 Feedback inhibition) [3].

An initial dose of ibutamoren causes a large spike in growth hormone levels (following normal physiologic pulsatile secretion) along with a large spike in cortisol. Subsequent and continued daily administration causes (comparatively) much smaller spikes in GH. IGF-1 levels become and stay elevated without a cortisol spike. If a dose is missed within 24 hours (half life of ibutamoren is 24 hours), IGF-1 will drop due to decreased liver stimulation from GH output. GHRH secretion is slowed by the continuously higher IGF-1 concentration, creating a safe negative feedback loop [3]. GHRPs DO NOT have a negative feedback loop because the GH spike is not sustained long enough (due to a short 4 hour half life) to allow for a sustained increase in IGF-1 (unless taken every few hours over a couple of days) GHRPs also do not allow for normal physiologic pulsatile function (which ibutamoren mimics). This negative feedback loop makes ibutamoren relatively very safe when compared to exogenous GH administration.

Growth Hormone Releasing Hormone Mimetics

These peptides mimic the hormone GHRH. GHRH is released from the hypothalamus and it binds to receptors on the anterior pituitary. The anterior pituitary then releases growth hormone into the bloodstream. The most popular GHRH mimetic is Sermorelin. It binds to the GHRH receptors of the hypothalamus and causes a marked increase in GH levels and IGF-1 levels.

Notice that GH Secretagogues bind to the GHS receptor and GHRH mimetics bind to the GHRH receptor. This means that there are two different pathways used to increase natural GH and IGF-1 production. If a GHRH mimetic is used along with a GHS, the synergistic effect should markedly increase natural GH and IGF-1 production.

IGF-1 in Relation to Testosterone

In a study titled “Testosterone administration increases insulin-like growth factor-I levels in normal men.” Researchers discovered just that [4]. Although testosterone (T) administration can increase insulin-like growth factor-I (IGF-I) when administered to hypogonadal men, no studies have examined whether this occurs in normal men. The present study was undertaken to determine if an increase in IGF-I may be part of the anabolic effect of androgens. Researchers enrolled 11 normal men in a randomized, double-blinded cross-over study. Subjects were assigned to receive either T enanthate (TE) (300 mg im, each week) or nandrolone (ND) decanoate (300 mg im, each week) for 6 weeks. After a washout period subjects were administered the alternate treatment. Pre- and posttreatment serum was analyzed for IGF-I by RIA after acid-ethanol extraction. Although GH levels were not significantly different after either TE or ND treatment, they tended to increase after TE treatment (1.23 +/- 0.28 ng/mL vs. 3.3 +/- 1.03 ng/mL) but remained unchanged after ND treatment (1.68 +/- 0.68 ng/mL vs. 1.89 +/- 0.64 ng/mL). Serum total T levels increased 32 +/- 0.05 nmol/L in the TE-treated men, but fell by 7 +/- 0.02 nmol/L in the ND-treated men (P < 0.0001). These data indicate that when normal men are given TE, serum IGF-I levels increase after 6 weeks of treatment.

IGF-1 Blood Test: Everything You Need to Know

 

IGF-1 stands for insulin-like growth factor. It's an essential hormone in the human body, and it's very similar to the insulin produced by your pancreas. An IGF-1 blood test is increasingly popular these days since this hormone plays a significant role in the numerous metabolic processes of the body.

But when was the last time you did an IGF-1 blood test? And why should you do one? Keep reading this article to learn everything you need to know about IGF-1 and its importance for human health.

What Is an IGF-1 Blood Test?

IGF-1 works in tandem with the growth hormone produced by your pituitary gland. The IGF-1 hormone plays an important role, particularly in childhood. It helps with the process of growing bones, muscles, and tissues.

An IGF-1 test uses a sample of your blood to measure how much of this hormone is circulating through your bloodstream. Having low levels of IGF-1 might show some effects, as you'll see later in this article.

In adulthood, IGF-1 continues to influence your health significantly. For example, it plays an essential role in tissue repairs, maintains healthy bones, and, more importantly, helps develop lean muscle mass.

What Does IGF-1 Do In the Body

Let's take a closer look at the most critical functions of IGF-1 to understand how important it is for your health. For example, IGF-1 is responsible for increasing muscle mass, provided that the person in question also works out regularly.

IGF-1 also maintains lean muscle and prevents a process known as atrophy. It also stimulates the growth of bones, and it provides energy for the body to do tissue repair processes such as for healing wounds and so on.

On top of that, IGF-1 also plays a crucial role in lipid metabolism. This means the process of burning fats stored throughout your body. In some cases, overweight and obese people might also struggle with IGF-1 deficiency as this hormone is vital for fat metabolism.

IGF-1 also helps with glucose metabolism. Glucose is also known as blood sugar and it's the main source of fuel for your body. Glucose is pushed by insulin into cells to produce energy. IGF-1 helps with this process, so the sugar in your blood is used effectively.

Symptoms of Having Low IGF-1 Levels

Having too much IGF-1 is rare, and it might happen during the early stages of life. In such cases, children grow very tall, and this condition is known as gigantism. Low IGF-1 issues are more prevalent, and they can affect both children and adults.

For example, here are the main symptoms of having too little IGF-1 in your system.

• Anxiety and depression
• Excessive fatigue
• Low exercise performance
• Loss of muscle mass
• Thin skin that gets wounded easily
• Reduced bone density

Some of these effects might be subtle, and you might not even know that they are caused by too little IGF-1 in your body. Also, many of these symptoms are shared by other health conditions, so it can be tricky to identify which ailment is the culprit.

That's why it's essential to do an IGF-1 test if you feel lethargic most of the time. Excessive tiredness might be caused by various factors such as low testosterone, low blood iron levels, but also because you might have too little IGF-1.

Causes of Low IGF-1

There are a few reasons why people might experience low levels of IGF-1 in the body. Remember that the pituitary gland produces a growth hormone that works in tandem with IGF-1. IGF-1 itself is mainly produced in the liver but also in other parts of the body.

One reason you might have low levels of IGF-1 is an underactive pituitary gland. This might be accompanied by low levels of thyroid hormones since the thyroid is also stimulated by the pituitary. In rare cases, pituitary tumors might prevent the proper release of growth hormone too.

Since IGF-1 works together with growth hormone, an insensitivity to GH might also cause symptoms such as the ones mentioned above. This problem can be genetic or inherited. For example, those with kidney or liver disease might develop an insensitivity to GH, which would result in low IGF-1 levels.

IGF-1 in Relation to Testosterone and ED

A couple of studies done in the last decade look at the link between IGF-1 and testosterone. It has been discovered that administering higher doses of testosterone exogenously might increase IGF-1 levels also. This means the administration of testosterone using creams, injections, or other methods.

Men on testosterone replacement therapy might benefit from this type of treatment by seeing their IGF-1 levels go up. The study data suggest that this increase is visible after at least six weeks of TRT.

At the same time, having higher IGF-1 levels might also alleviate erectile dysfunction in some men. ED is a prevalent problem for those with low testosterone levels and/or seniors. A study found that increasing IGF-1 levels (as well as GH levels) could improve sexual function in men.

Having more IGF-1 is likely more beneficial for adults than having less of it. That's why you might be interested in natural ways you can increase IGF-1. This is entirely possible, and one of the simplest ways to do it is to lose body fat.

Excessive fat automatically lowers IGF-1 levels, so you might want to increase your weekly exercising time to lose weight. Fasting can also be used to increase IGF-1 levels. There are many types of fasting, and intermittent fasting is one of the most popular types.

Order The IGF-1 Lab Test Today!

As you can see, the increasing interest in IGF-1 is justified as this hormone is so important when it comes to your health. If you experience some of the symptoms mentioned above or you want to see how you stand, make sure that you order an IGF-1 blood test as soon as possible.

To get excellent value for money and receive the results in just a few business days, go to DiscountedLabs.com and order the affordable IGF-1 lab test today!

 

IGF-1 Reference Range(s)

 

Pediatric	Male (ng/mL)	Female (ng/mL)
<1 Years	14-142	17-185
1-1.9 Years	12-134	15-175
2-2.9 Years	12-135	16-179
3-3.9 Years	30-155	38-214
4-4.9 Years	28-181	34-238
5-5.9 Years	31-214	37-272
6-6.9 Years	38-253	45-316
7-7.9 Years	48-298	58-367
8-8.9 Years	62-347	76-424
9-9.9 Years	80-398	99-483
10-10.9 Years	100-449	125-541
11-11.9 Years	123-497	152-593
12-12.9 Years	146-541	178-636
13-13.9 Years	168-576	200-664
14-14.9 Years	187-599	214-673
15-15.9 Years	201-609	218-659
16-16.9 Years	209-602	208-619
17-17.9 Years	207-576	185-551

 

Adult	(ng/mL)
18-19.9 Years	108-548
20-24.9 Years	83-456
25-29.9 Years	63-373
30-39.9 Years	53-331
40-49.9 Years	52-328
50-59.9 Years	50-317
60-69.9 Years	41-279
70-79.9 Years	34-245
>80 Years	34-246

 

Z-Score (Male)	-2.0 - +2.0 SD
Z-Score (Female)	-2.0 - +2.0 SD

 

References:

1. Pastuszak AW, Liu JS, Vij A, Mohamed O, Sathyamoorthy K, Lipshultz LI, Khera M. IGF-1 levels are significantly correlated with patient-reported measures of sexual function. Int J Impot Res. 2011 Sep-Oct;23(5):220-6

2. Smith, Roy G. Human Growth Hormone Research and Clinical Practice.

3. Hobbs CJ, Plymate SR, Rosen CJ, Adler RA. Testosterone administration increases insulin-like growth factor-I levels in normal men. J Clin Endocrinol Metab. 1993 Sep;77(3):776-9.

4. Agnieszka Swiecicka, Mark Lunt, Tomas Ahern, Terence W. O'Neil. Higher Anabolic Hormone Levels Predict Lower Risk of Worsening Frailty in Men: Prospective Results from the European Male Ageing Study. Presented at Endocrine Society Annual Meeting 2017