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Relationship Between IGF-1 And Growth Hormone

Written by Author - Authors Medical experts of the National HRT Clinic - March 11, 2016

Growth Hormone and IGF-1

There may be no more important chemical balance in the body than that of the relationship between IGF-1 and growth hormone (GH). IGF-1 or insulin growth factor 1, release relies on the signals from GH to the liver. In turn, IGF-1 regulates how much GH the pituitary gland secretes based on signals from the hypothalamus, which measures IGF-1 levels in the blood.

Maintaining the synergy between HGH and IGF-1 in the body is critical to optimal health and aging. The growth hormone/IGF axis is a tightly regulated feedback loop that includes two chemicals released by the hypothalamus and sent to the pituitary gland:

  • Growth hormone-releasing hormone (GHRH): stimulates growth hormone production in the pituitary gland
  • Somatostatin: inhibits growth hormone production

Maintaining balance in the relationship between IGF-1 and growth hormone is crucial to optimal health.

What Is IGF-1?

As we begin our look at the relationship between IGF-1 and growth hormone, it will help to understand the role of insulin growth factor 1 in the body.

IGF-1 is a polypeptide hormone consisting of 70 amino acids. It has endocrine, autocrine, and paracrine effects on the body. Approximately 75% of circulating IGF-1 comes from the liver. Bodily tissues produce the remainder of IGF-1.

Here are some facts about IGF-1:

  • Method of Secretion: Production of IGF-1 occurs in the following ways:
    • The majority of IGF-1 is synthesized in the liver under growth hormone control and regulation
    • Peripheral tissues, including bone, synthesize autocrine/paracrine IGF-1 via GH regulation
  • Function: Whereas liver-produced IGF-1 enters the bloodstream to influence all areas of the body and brain, much of what is produced by peripheral tissues works locally. Some peripheral IGF-1 does enter the circulation to impact other areas. Functions of IGF-1 include:
    • Stimulating amino acid and glucose uptake in muscle
    • Mediating the cell regenerating effects of GH on tissues, muscles, bones, skin, organs, hair, and nails
    • Exerting a protective influence on certain gastrointestinal disorders
    • Regulating neuronal structure and functions in the brain that support processing, learning, memory, and emotional stability
    • Inhibiting early cellular death (apoptosis)
    • Providing neuroprotective benefits for nerve repair
    • Promoting lipid metabolism
    • Stimulating nitric oxide (NO) production

With low HGH and IGF-1 levels, a person may experience cognitive impairment, weight gain, muscle loss, reduced bone density, and many other physiological changes.

What Is Growth Hormone?

Also called somatotropin, growth hormone is undeniably one of if not the most influential hormone in the body. Maintaining the relationship between IGF-1 and growth hormone is of vital importance to health as adults continue to age. Although the body is no longer growing, its cells are in a constant state of renewal, regeneration, and growth. That is why, as GH levels decline with age, many adults experience the following changes:

  • Thinning or loss of hair
  • Reduced collagen and elastin production resulting in wrinkles and sagging skin
  • Muscle and bone loss
  • Height shrinkage
  • Reduced internal organ size resulting in decreased functions
  • Forgetfulness and impaired cognitive processing

Here are some facts about growth hormone:

  • Method of Secretion: Production of GH occurs in the following ways:
    • Low IGF-1 levels tell the hypothalamus to send GHRH to the pituitary gland to stimulate the somatotrophs (cells that produce GH) to secrete somatotropin
    • High IGF-1 levels tell the hypothalamus to send somatostatin to the pituitary gland to inhibit GH secretion
    • Ghrelin, also known as the hunger hormone, enters the bloodstream from the stomach and travels to the hypothalamus as a signal to stimulate growth hormone production
  • Function: Growth hormone functions influence all areas of the body, primarily at the cellular level, where it stimulates cell regeneration. Other essential GH functions include:
    • Metabolism regulation and lipolysis (fat breakdown)
    • Support of cognitive functions and emotional well-being via GH receptors throughout the various regions of the brain
    • Stimulation of thymus activity to support immune responses
    • Opposition of insulin activity for blood sugar regulation
    • Regulation of temperature control and sensitivity in the body
    • Maintenance of internal organ structure for proper functions

Together, HGH and IGF-1 regulate many critical areas of physiological and mental functions.

What Is the Difference Between IGF-1 and Growth Hormone?

As we look now at the difference between HGH and IGF-1, it may appear as though they are indeed similar in many ways. However, without growth hormone, the body will likely experience a significant decline in IGF-1 levels.

The relationship between IGF-1 and growth hormone is one in which IGF-1 plays the supporting role. As mediator of many effects of GH on the body’s cells, IGF-1 supports growth hormone actions.

Another crucial difference between IGF-1 and HGH is that IGF-1 binds to insulin receptors to promote insulin-like actions – a function that GH does not have. Whereas GH suppresses insulin actions, IGF-1 can enhance them. As GH levels decline in response to increased IGF-1 concentrations, insulin actions in the liver increase.

How Do IGF-1 and Growth Hormone Influence Each Other?

The influence of HGH and IGF-1 together is what helps the body maintain structural integrity. With GH promoting IGF-1 release, and insulin growth factor 1 mediating growth hormone cellular activities, the skin, tissues, hair, muscles, organs, and bones become stronger.

Through the balanced relationship between IGF-1 and growth hormone, brain functions, metabolism, and tissue repair improve.

In other words, protecting this delicate hormonal balance in the body is critical to optimal health and well-being.

To learn more about GH and IGF-1, please contact National HRT for a confidential phone consultation at no charge.

Medically reviewed by   Reviewers National HRT Staff - Updated on November 21, 2023

Please note that the information provided in this article is for informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified healthcare provider with any questions you may have regarding a medical condition or treatment.