Growth Hormone

How Growth Hormone Works

Growth hormone operates through direct and indirect mechanisms:

Direct Effects

• Acts directly on fat cells to promote lipolysis (fat breakdown)
• Stimulates protein synthesis in various tissues
• Influences carbohydrate metabolism

Indirect Effects (via IGF-1)

• Stimulates liver to produce IGF-1
• IGF-1 mediates most growth-promoting effects
• Effects on bone, muscle, and organ growth

Growth Hormone Release Pattern

GH is released in pulses, not continuously:

Factor	Effect on GH
Sleep (especially deep sleep)	Major release pulse
Exercise (high intensity)	Acute increase
Fasting	Increased release
GHRH	Stimulates release
Ghrelin	Stimulates release
Somatostatin	Inhibits release
High blood sugar	Suppresses release

Growth Hormone Throughout Life

Childhood and Adolescence

• Essential for linear growth
• Peak production during puberty
• Deficiency causes growth failure

Adulthood

• Production gradually declines (~14% per decade)
• Maintains body composition and metabolism
• Supports tissue repair

Aging

• Significant reduction (“somatopause”)
• Associated with increased body fat, decreased muscle
• Area of ongoing research

GH Secretagogues in Research

Rather than administering GH directly, researchers study peptides that stimulate natural GH release:

GHRH Analogs

• Sermorelin - Modified GHRH fragment
• CJC-1295 - Long-acting GHRH analog
• Tesamorelin - FDA-approved for HIV lipodystrophy

Ghrelin Mimetics

• Ipamorelin - Selective GH secretagogue
• GHRP-6 - Growth hormone releasing peptide
• GHRP-2 - Similar to GHRP-6 with different selectivity

GH Secretagogues vs Exogenous GH

Aspect	Secretagogues	Exogenous GH
Source of GH	Stimulates natural production	Provides synthetic GH
Pulsatility	Maintains natural patterns	Continuous levels
Feedback	Preserves regulation	May suppress natural production
IGF-1 levels	Variable, regulated	Can be supraphysiological

Frequently Asked Questions

What’s the difference between GH and steroids?

Growth hormone is a peptide hormone that affects growth and metabolism. Anabolic steroids are synthetic versions of testosterone. They have different structures, mechanisms, effects, and side effect profiles. GH works partly through IGF-1; steroids work through androgen receptors.

Why do some peptides increase growth hormone?

Certain peptides mimic natural signaling molecules (GHRH, ghrelin) that tell the pituitary to release growth hormone. By activating these pathways, they stimulate the body’s own GH production rather than providing external GH.

Does growth hormone decline with age?

Yes. GH production decreases approximately 14% per decade after young adulthood. By age 60, many people produce only a fraction of their youthful GH levels. This decline contributes to age-related changes in body composition.