Insulin-like Growth Factor (IGF-1)

Insulin-Like Growth Factor 1 (IGF-1) is a hormone structurally similar to insulin that plays a critical role in growth, repair, and metabolism. It is produced primarily in the liver in response to growth hormone (GH) stimulation and acts as a key mediator of GH’s anabolic effects. IGF-1 promotes cell growth, protein synthesis, bone formation, and tissue regeneration, making it essential for maintaining muscle mass, bone strength, and metabolic balance throughout life.

IGF-1 is one of the body’s most important markers of cellular health and longevity.

• In younger women, IGF-1 supports muscle development, fertility, and bone mineralization.

• In adults, it helps maintain lean mass, energy levels, and cardiovascular resilience.
  

Low IGF-1 levels are associated with sarcopenia, osteoporosis, fatigue, poor recovery, and insulin resistance, while excessively high levels may contribute to acromegaly, insulin resistance, and increased cancer risk due to enhanced cellular proliferation.
Optimal IGF-1 levels represent a balance — too little may accelerate aging, while too much can overstimulate growth pathways.

IGF-1 levels are dynamic and influenced by both biological and lifestyle factors:

• Menstrual Cycle: Slight increases occur during the luteal phase when estrogen is higher.

• Age and Menopause: IGF-1 peaks in late adolescence and declines steadily with age. After menopause, levels are significantly lower, contributing to reduced muscle and bone density.

• Pregnancy: IGF-1 rises, particularly in the third trimester, to support fetal growth and placental function.

• Nutrition & Body Composition: Adequate protein and calorie intake support healthy IGF-1 production. Conversely, caloric restriction or malnutrition suppresses it.

• Exercise: Regular resistance training elevates IGF-1, while inactivity or overtraining can suppress it.

• Stress & Sleep: Chronic stress and poor sleep can lower IGF-1 via reduced GH secretion.

Childhood & Puberty
During childhood, IGF-1 is low but rises dramatically in puberty as GH and sex hormones increase. This surge supports the adolescent growth spurt, bone elongation, and reproductive maturation.

Reproductive Years
In women of reproductive age, IGF-1 helps maintain tissue repair, fertility, and metabolic health. It interacts closely with estrogen and insulin to regulate ovarian follicle growth and energy metabolism. High IGF-1 levels during this stage have been linked to polycystic ovary syndrome (PCOS), as IGF-1 enhances ovarian androgen production.

Perimenopause
As estrogen and GH secretion decline, IGF-1 levels become more variable. This shift often coincides with decreased muscle mass, reduced exercise recovery, and metabolic slowing. Supporting IGF-1 naturally through nutrition and resistance training becomes especially important in this phase.

Postmenopause
IGF-1 levels are significantly lower after menopause due to reduced GH and estrogen. This decline is associated with loss of bone density, frailty, and increased cardiometabolic risk. Optimizing sleep, maintaining lean muscle, and ensuring adequate protein intake can help preserve IGF-1 activity in later life.

If IGF-1 Is Low:

1. Prioritize Protein and Nutrient-Dense Foods: Ensure adequate intake of complete proteins (e.g., eggs, fish, lean meats, legumes) and essential amino acids like leucine, which stimulate GH and IGF-1 production.
   

2. Engage in Strength Training: Resistance exercise is one of the most effective ways to elevate IGF-1 and support bone and muscle health.
   

3. Optimize Sleep and Recovery: Deep sleep is when growth hormone peaks, driving IGF-1 synthesis. Aim for 7–9 hours of quality sleep per night.
   

4. Balance Calories and Avoid Chronic Restriction: Prolonged fasting or very low-calorie diets suppress IGF-1. Incorporate nourishing whole foods and adequate energy to support endocrine function.
   

5. Address Hormonal or Pituitary Dysfunction: Chronically low IGF-1 with fatigue and muscle wasting may indicate GH deficiency or pituitary dysfunction; medical evaluation may be required.
   

If IGF-1 Is High:

1. Monitor Insulin and Glucose Levels: Chronically high IGF-1 can accompany insulin resistance — review your fasting glucose, HbA1c, and insulin.
   

2. Moderate Protein Intake: Excessive animal protein may raise IGF-1; consider balancing with more plant-based sources.
   

3. Manage Stress: Chronic cortisol elevation can disrupt GH–IGF-1 signaling, amplifying metabolic imbalance.
   

4. Medical Evaluation: Persistently elevated IGF-1 may warrant investigation for conditions such as acromegaly or growth hormone–secreting pituitary tumors.

2. Helle, S. I., Anker, G. B., Meadows, K. A., Holly, J. M., & Lønning, P. E. (1998). Alterations in the insulin-like growth factor system during the menstrual cycle in normal women. Maturitas, 28(3), 259–265. https://doi.org/10.1016/s0378-5122(97)00088-1

3. Juul, A., Scheike, T., Pedersen, A. T., et al. (1997). Changes in serum concentrations of growth hormone, insulin, insulin-like growth factor, and binding proteins during the menstrual cycle. Human Reproduction, 12(10), 2123–2128. https://doi.org/10.1093/humrep/12.10.2123

4. Thierry van Dessel, H. J., Chandrasekher, Y., Yap, O. W., et al. (1996). Serum and follicular fluid levels of IGF-I, IGF-II, and IGF-binding proteins during the normal menstrual cycle. The Journal of Clinical Endocrinology and Metabolism, 81(3), 1224–1231. https://doi.org/10.1210/jcem.81.3.8772603

5. Druckmann, R., & Rohr, U. D. (2002). IGF-1 in gynecology and obstetrics: Update 2002. Maturitas, 41(Suppl 1), S65–S83. https://doi.org/10.1016/s0378-5122(02)00016-6

6. Monaghan, J. M., Godber, I. M., Lawson, N., et al. (2004). Longitudinal changes of insulin-like growth factors and their binding proteins throughout normal pregnancy. Annals of Clinical Biochemistry, 41(3), 220–226. https://doi.org/10.1258/000456304323019596

7. Helle, S. I., Ekse, D., Holly, J. M., & Lønning, P. E. (2002). The IGF system in healthy pre- and postmenopausal women: Relations to sex steroids. The Journal of Steroid Biochemistry and Molecular Biology, 81(1), 95–102. https://doi.org/10.1016/s0960-0760(02)00052-3

8. Holmes, M. D., Pollak, M. N., & Hankinson, S. E. (2002). Lifestyle correlates of plasma IGF-I and IGF-binding protein concentrations. Cancer Epidemiology, Biomarkers & Prevention, 11(9), 862–867.

9. Karl, J. P., Alemany, J. A., & Koenig, C. (2009). Diet, body composition, and physical fitness influences on IGF-I bioactivity in women. Growth Hormone & IGF Research, 19(6), 491–496. https://doi.org/10.1016/j.ghir.2009.04.001