Hormone Biomarkers: Insulin-like Growth Factor (IGF-1)

Optimal Takeaways

Insulin-like growth factor-1 is a peptide that regulates the effects of growth hormone throughout the body. Blood levels of IGF-1 reflect levels of circulating growth hormone but are not as prone to variation. Low levels may be seen in chronic disease, malnutrition, and dwarfism. Higher levels may be associated with hyperpituitarism, obesity, pregnancy, gigantism, and increased risk of certain cancers.

Standard Range: 53 - 331 ng/mL (6.94 - 43.36 nmol/L)

The ODX Range: 92 - 300 ng/mL (12.12 - 39.22 nmol/L)  

Low levels of IGF-1 are seen with growth hormone deficiency or resistance, pituitary tumor or reduced function, liver disease, kidney disease, hypothyroidism, inflammatory bowel disease, malnutrition, and dwarfism. Estrogen therapy can decrease IGF-1 levels (Pagana 2019). Low IGF-1 is also associated with impairment of endothelium-dependent vasodilation and increased risk of atherosclerosis and CVD (Higashi 2019). Low IGF-1 is also found in fibromyalgia and other chronic diseases (Braverman 2013), including osteoporosis, heart disease, and impaired cognition (Borofsky 2002).

High levels of IGF-1 are seen with acromegaly, gigantism, hyperpituitarism, obesity, pregnancy, and precious puberty (Pagana 2019). Elevated levels may be associated with increased cancer risk including breast, prostate, colorectal, and lung (Borofsky 2002).

Overview

Insulin-like growth factor-1, also called somatomedin C, is one of the most commonly measured somatomedins, the peptides that regulate the effects of growth hormone (GH) various tissues. Measurement of IGF-1 reflects mean blood levels of growth hormone without the wide variations seen in measuring GH itself. IGF-1 is not affected by time of day, exercise, or food intake. Levels of IGF-1 may help evaluate growth abnormalities including short stature and acromegaly (Pagana 2019).

IGF-1 itself is considered an anabolic hormone and together with growth hormone it regulates growth early in the lifespan and helps maintain anabolic processes in adulthood. Levels of IGF-1 and GH decline later in life during a period referred to as “somatopause.” Somatopause can contribute to loss of muscle, bone mass, and strength, as well as an increase in adiposity, arterial hypertension, dyslipidemia, cardiovascular disease, and cognitive decline (Rahmani 2019).

However, earlier studies suggest an increase in IGF-1 bioactivity may be associated with increased risk of cancer including prostate, colorectal, and premenopausal breast cancer. Researchers note that these associations may not be direct and may be linked with excess food/energy intake (Yu 2000). On the other hand, a meta-analysis found that low IGF-1 was associated with ovarian cancer (Gianuzzi 2016).

Very low levels of IGF-1 likely indicate a growth hormone deficiency. In adults, growth hormone deficiency is characterized by increased CRP, dyslipidemia, abdominal obesity, decreased lean body mass, atherosclerosis, compromised psychological health, and increased mortality. During GH replacement therapy, concurrent increases in IGF-1 levels were associated with improved bone mineral density, fibromyalgia, cognitive performance, head trauma, insulin sensitivity, and IQ. For example, symptoms of head trauma such as memory deficits, anxiety, and depression improved when IGF-1 levels increased from 24.64 ng/mL (3.22 nmol/L) to 120.75 ng/mL (15.79 nmol/L). Researchers suggest that IGF-1 levels in the high end of normal may help reverse chronic disease complications (Braverman 2013).

In a study of 2792 healthy Chinese adults, the median IGF-1 level was 374.1 ng/mL (48.9 nmol/L) in healthy 18-year-olds and then declined steadily with age. Median IGF-1 at age 35-39 was 180.1 ng/mL (23.55 nmol/L) and 92.7 ng/mL (12.12 nmol/L) over the age of 70 (Zhu 2017).

In an earlier study of 26 healthy men and women, measurement of IGF-1 levels over time found the overall mean IGF-1 level for all participants (aged 25.5-80.3 years) was 290.7 ng/mL (38 nmol/L) (Borofsky 2002). Severe restricting of caloric intake by 50% can significantly reduce circulating IGF-1 in the short-term, decreasing levels by a mean of 36.57 ng/ml (4.79 nmol/L) (Rahmani 2019).

It is especially important to repeat IGF-1 measurement with the same method as variation between immunoassays can be considerable (Chanson 2016).

References

Borofsky, Nancy D et al. “Utility of insulin-like growth factor-1 as a biomarker in epidemiologic studies.” Clinical chemistry vol. 48,12 (2002): 2248-51.

Braverman, E et al. “Low and Normal IGF-1 Levels in Patients with Chronic Medical Disorders (CMD) is Independent of Anterior Pituitary Hormone Deficiencies: Implications for Treating IGF-1 Abnormal Deficiencies with CMD.” Journal of genetic syndromes & gene therapy vol. 4,123 (2013): 1000123. doi:10.4172/2157-7412.1000123

Chanson, Philippe et al. “Reference Values for IGF-I Serum Concentrations: Comparison of Six Immunoassays.” The Journal of clinical endocrinology and metabolism vol. 101,9 (2016): 3450-8. doi:10.1210/jc.2016-1257

Gianuzzi, Ximena et al. “Insulin growth factor (IGF) 1, IGF-binding proteins and ovarian cancer risk: A systematic review and meta-analysis.” Maturitas vol. 94 (2016): 22-29. doi:10.1016/j.maturitas.2016.08.012

Higashi, Yusuke et al. “IGF-1 and cardiovascular disease.” Growth hormone & IGF research : official journal of the Growth Hormone Research Society and the International IGF Research Society vol. 45 (2019): 6-16. doi:10.1016/j.ghir.2019.01.002 [R}

Pagana, Kathleen Deska; Pagana, Timothy J.; Pagana, Theresa N. Mosby's Diagnostic and Laboratory Test Reference. Elsevier Health Sciences. 2019.

Rahmani, Jamal et al. “The influence of fasting and energy restricting diets on IGF-1 levels in humans: A systematic review and meta-analysis.” Ageing research reviews vol. 53 (2019): 100910. doi:10.1016/j.arr.2019.100910 v

Yu, H, and T Rohan. “Role of the insulin-like growth factor family in cancer development and progression.” Journal of the National Cancer Institute vol. 92,18 (2000): 1472-89. doi:10.1093/jnci/92.18.1472

Zhu, Huijuan et al. “Reference ranges for serum insulin-like growth factor I (IGF-I) in healthy Chinese adults.” PloS one vol. 12,10 e0185561. 4 Oct. 2017, doi:10.1371/journal.pone.0185561