Skip to main content

Fundamentals

The subtle shifts within your body, perhaps a gradual thinning of hair, a change in its texture, or a general sense of diminished vitality, often prompt an earnest, personal inquiry. These experiences often represent clear signals from your internal systems. Such shifts are interconnected with your endocrine network.

Many individuals describe a feeling of being disconnected from their former selves, noticing changes in energy, sleep patterns, and even the resilience of their hair. This path of self-discovery, understanding your own biological systems, is a significant step toward restoring a sense of equilibrium and capability.

Hair health, while seemingly a superficial concern, is a sensitive barometer of systemic well-being. It reflects the complex interaction of hormones, metabolic efficiency, and cellular nourishment. When the body’s internal messaging services ∞ the hormones ∞ are out of sync, or when the basic metabolic processes falter, one visible manifestation can be changes in hair density, growth cycles, and overall quality.

This link is rooted in the basic biology of the hair follicle, extending beyond mere anecdote, as it is a highly active and metabolically demanding structure.

Hair health serves as a visible indicator of the body’s internal hormonal and metabolic equilibrium.

Illustrating citrus' intricate fibrous architecture, this highlights fundamental cellular function vital for hormone optimization and metabolic health. It metaphorically represents precise clinical protocols targeting tissue integrity for comprehensive patient wellness and bioregulation

The Endocrine System and Hair Follicle Dynamics

Your endocrine system functions as a sophisticated regulatory network, with various glands producing chemical messengers that travel through the bloodstream to influence nearly every cell and tissue. These messengers, known as hormones, regulate a vast array of bodily processes, including growth, metabolism, mood, and reproductive function. Hair follicles, the tiny organs responsible for hair production, are particularly responsive to these hormonal signals.

Androgens, a class of hormones that includes testosterone and dihydrotestosterone (DHT), play a notable role in hair growth patterns. While often associated with male characteristics, these hormones are present in both men and women and influence hair follicles differently depending on their location on the body and individual genetic predispositions.

For instance, in genetically susceptible individuals, DHT can miniaturize scalp hair follicles, causing thinning. Conversely, adequate levels of other hormones, such as thyroid hormones and estrogens, are essential for maintaining healthy hair growth cycles and follicle vitality.

A male patient’s thoughtful expression in a clinical consultation underscores engagement in personalized hormone optimization. This reflects his commitment to metabolic health, enhanced cellular function, and a proactive patient journey for sustainable vitality through tailored wellness protocols

Hormonal Balance and Cellular Health

Maintaining a precise hormonal balance is essential for cellular health across all tissues, including those that support hair. When there is an imbalance, whether due to age-related decline, stress, environmental factors, or underlying health conditions, the body’s ability to maintain peak cellular function can be compromised. This can result in a cascade of effects, affecting everything from energy production within cells to the integrity of structural proteins.

The body’s ability to regenerate and repair tissues relies heavily on efficient cellular communication and strong metabolic pathways. Hair follicles, with their rapid cell turnover, require a consistent supply of nutrients and precise hormonal signaling to sustain their growth phases.

Any disruption in this delicate equilibrium can shift follicles into a resting or shedding phase prematurely, causing noticeable hair loss or reduced density. Grasping these basic biological principles offers a framework for examining how targeted interventions might aid systemic vitality, including hair health.

Common indicators that may suggest a need to assess hormonal and metabolic health include:

  • Hair Thinning ∞ A reduction in hair density or diameter across the scalp.
  • Fatigue ∞ Persistent tiredness despite adequate rest.
  • Mood Shifts ∞ Unexplained changes in emotional state or irritability.
  • Sleep Disturbances ∞ Difficulty falling or staying asleep.
  • Changes in Body Composition ∞ Unintended weight gain or loss, or shifts in muscle mass.

Intermediate

Addressing concerns about hair health, particularly when linked to systemic changes, requires a clinically informed approach that considers the body’s interconnected systems. Peptide therapies, when incorporated into a broader hormonal optimization strategy, offer a distinct avenue for aiding systemic physiological function, which can indirectly benefit hair vitality. These protocols aim to restore balance to the body’s internal signaling networks, moving beyond mere symptom management.

Hormonal optimization protocols, such as those involving

Testosterone Replacement Therapy

(TRT) for men and women, are designed to normalize physiological levels of central endocrine messengers. For men experiencing symptoms of low testosterone, a standard protocol might involve weekly intramuscular injections of

Testosterone Cypionate

. This is often combined with

Gonadorelin

to help preserve natural testosterone production and fertility, and

Anastrozole

to manage estrogen conversion. Women, too, can benefit from precise testosterone supplementation, typically via subcutaneous injections of

Testosterone Cypionate

at lower doses, often alongside

Progesterone

based on their menopausal status. These interventions seek to re-establish a hormonal environment conducive to systemic health, which includes aiding the health of hair follicles.

Peptide therapies, when combined with hormonal optimization, can support hair health by recalibrating the body’s internal signaling.

Hands joined during a compassionate patient consultation for hormone optimization. This reflects crucial clinical support, building trust for personalized wellness journeys toward optimal endocrine health and metabolic balance

Growth Hormone Peptide Protocols

Beyond direct hormonal adjustments, specific peptide therapies can play a supportive role by influencing the body’s natural growth hormone axis. Growth hormone (GH) is a potent anabolic hormone that influences cellular repair, protein synthesis, and metabolic rate. While direct GH administration is highly regulated, certain peptides act as

Growth Hormone Secretagogues

(GHS), prompting the body’s own pituitary gland to release more GH. This approach utilizes the body’s innate capacity for self-regulation.

Commonly utilized growth hormone-releasing peptides include:

  • Sermorelin ∞ A synthetic analog of Growth Hormone-Releasing Hormone (GHRH), it prompts the pituitary to release GH in a pulsatile, physiological manner.
  • Ipamorelin / CJC-1295 ∞ These peptides work synergistically. Ipamorelin is a selective GH secretagogue, while CJC-1295 (without DAC) is a GHRH analog that prolongs the half-life of GHRH, leading to sustained GH release.
  • Tesamorelin ∞ Another GHRH analog, often used for its specific effects on visceral fat reduction, which can better metabolic health.
  • Hexarelin ∞ A potent GHS that also has some direct effects on cardiac tissue and wound healing.
  • MK-677 ∞ An oral GH secretagogue that increases GH and IGF-1 levels by mimicking ghrelin.

The systemic benefits of optimized growth hormone levels ∞ better cellular repair, increased protein synthesis, and better metabolic function ∞ can indirectly aid the highly active cells of the hair follicle. Hair growth is a metabolically demanding process, and a more strong anabolic environment can supply the necessary resources for stronger, healthier hair.

The dune's graceful contours and detailed ripples portray intricate endocrinological pathways and precise physiological adaptation. It illustrates hormonal balance for cellular function excellence, enhancing metabolic health and ensuring therapeutic progress through hormone optimization in clinical wellness

Other Targeted Peptides and Their Systemic Influence

Other peptides, while not directly aimed at hair, add to systemic physiological balance that can benefit hair health.

Pentadeca Arginate

(PDA), for instance, is recognized for its roles in tissue repair, lessening inflammation, and aiding healing. Chronic inflammation or impaired tissue repair mechanisms can negatively affect hair follicles, so aiding these processes systemically can establish a more favorable environment for hair growth. Similarly, peptides like

PT-141

, primarily used for sexual health, can enhance systemic well-being and lessen stress, which are factors that indirectly influence hair vitality.

The table below outlines a comparison of common hormonal and peptide protocols and their main systemic benefits, which can collectively add to a more strong environment for hair health.

Protocol Type Primary Agents Key Systemic Benefits Indirect Hair Health Support
Male Testosterone Optimization Testosterone Cypionate, Gonadorelin, Anastrozole Better energy, mood, muscle mass, bone density, libido. Increased cellular anabolism, lessened systemic inflammation, better nutrient delivery to follicles.
Female Testosterone Balance Testosterone Cypionate, Progesterone, Pellets Balanced mood, increased libido, better bone density, lessened hot flashes. Optimized follicular growth cycles, lessened stress-related hair shedding, better scalp circulation.
Growth Hormone Secretagogues Sermorelin, Ipamorelin/CJC-1295, MK-677 Increased cellular repair, increased lean muscle, fat reduction, better sleep quality. Prompting of protein synthesis in follicles, better cellular regeneration, better nutrient utilization for hair growth.
Tissue Repair Peptides Pentadeca Arginate (PDA) Lessen inflammation, accelerated wound healing, better tissue integrity. Establishment of a less inflammatory scalp environment, aid for microcirculation around follicles.

These protocols, when carefully administered and monitored, seek to normalize physiological equilibrium, establishing a more resilient internal environment where systems, including hair follicles, can function at their peak. The objective is to aid the body’s inherent capacity for health and regeneration, rather than simply treating isolated symptoms.

Academic

The complex connection between systemic hormonal balance and the localized biology of the hair follicle represents a fascinating area of clinical inquiry. While the direct mechanisms by which peptide therapies influence hair health are still being elucidated, their significant effect on the broader endocrine and metabolic landscape offers a strong justification for their indirect aid of follicular vitality.

The hair follicle, a highly dynamic mini-organ, is highly sensitive to fluctuations in circulating hormones, growth factors, and the local inflammatory milieu.

Consider the

Hypothalamic-Pituitary-Gonadal (HPG) axis

, a key regulatory pathway controlling sex hormone production. The hypothalamus releases

Gonadotropin-Releasing Hormone (GnRH)

, which prompts the pituitary gland to secrete

Luteinizing Hormone (LH)

and

Follicle-Stimulating Hormone (FSH)

. These gonadotropins then act on the gonads (testes in men, ovaries in women) to produce sex steroids, such as testosterone and estrogen. Peptides like Gonadorelin, a synthetic GnRH analog, directly influence this axis, preserving testicular function in men undergoing testosterone replacement, thereby preserving endogenous hormone production and fertility. This systemic restoration of balance to the HPG axis adds to a more stable hormonal environment, which can lessen the adverse effects of notable hormonal fluctuations on hair follicle cycling.

The hair follicle, a dynamic mini-organ, is highly responsive to systemic hormonal and metabolic shifts.

Detailed leaf venation symbolizes intricate physiological pathways vital for hormone optimization and metabolic health. It represents foundational cellular function, nutrient delivery, and tissue regeneration crucial for systemic balance and clinical wellness

Growth Hormone Axis and Anabolic Signaling

The

Growth Hormone (GH) / Insulin-like Growth Factor 1 (IGF-1) axis

plays an essential role in cellular proliferation, differentiation, and tissue repair. GH secretagogues, such as Sermorelin and Ipamorelin, prompt the pulsatile release of endogenous GH from the anterior pituitary. This results in increased hepatic production of IGF-1, a potent anabolic mediator. IGF-1 receptors are present on dermal papilla cells within the hair follicle, suggesting a direct role in regulating hair growth. Studies indicate that IGF-1 advances the proliferation of hair matrix cells and prolongs the anagen (growth) phase of the hair cycle.

The systemic elevation of GH and IGF-1 levels, achieved through targeted peptide administration, can therefore supply a more strong anabolic environment for hair follicles. This includes increased protein synthesis, better nutrient delivery, and more efficient cellular repair mechanisms within the scalp. The table below illustrates the molecular targets and potential hair-related benefits of central growth hormone-modulating peptides.

Peptide Mechanism of Action Molecular Targets Potential Hair Health Benefit
Sermorelin GHRH analog, prompts pituitary GH release GHRH receptors on somatotrophs Increased IGF-1, increased anagen phase, better follicle metabolism.
Ipamorelin Selective GH secretagogue, ghrelin mimetic Ghrelin receptors (GHSR-1a) on pituitary Sustained GH pulsatility, lessened cortisol, better cellular repair in follicles.
CJC-1295 Long-acting GHRH analog GHRH receptors on somatotrophs Prolonged GH and IGF-1 elevation, sustained anabolic signaling to hair matrix.
MK-677 Oral ghrelin mimetic Ghrelin receptors (GHSR-1a) Chronic GH and IGF-1 elevation, systemic anabolic effects aiding hair growth.
White, smooth, polished stones with intricate dark veining symbolize purified compounds essential for hormone optimization and metabolic health. These elements represent optimized cellular function and endocrine balance, guiding patient consultation and the wellness journey with clinical evidence

Metabolic Health, Inflammation, and Hair Follicle Resilience

Beyond direct hormonal and growth factor signaling, the systemic metabolic health of an individual significantly influences hair follicle resilience. Conditions characterized by metabolic dysregulation, such as

insulin resistance

or chronic low-grade inflammation, can negatively affect hair growth. Insulin resistance can alter androgen metabolism, potentially increasing local DHT activity in susceptible follicles. Chronic inflammation, on the other hand, can establish a hostile microenvironment around the hair follicle, causing oxidative stress and premature follicular senescence.

Peptides that indirectly aid metabolic health or lessen inflammation can therefore add to hair vitality. Tesamorelin, while mainly known for its role in lessening visceral adiposity, can enhance insulin sensitivity and lessen inflammatory markers, establishing a more favorable systemic environment. Pentadeca Arginate (PDA), with its tissue-repairing and anti-inflammatory properties, could theoretically aid scalp health by lessening localized inflammatory responses that might otherwise compromise follicular function.

The complex network of biological axes ∞ HPG, GH/IGF-1, and metabolic pathways ∞ demonstrates a reflection of systemic equilibrium; hair health is not an isolated phenomenon. By optimizing these basic physiological systems through targeted peptide and hormonal interventions, a more resilient and conducive environment for hair follicle function can be formed, resulting in better hair density and quality. This thorough, systems-biology perspective highlights the potential for indirect, yet notable, aid for hair health during broader hormonal optimization efforts.

A vibrant, effervescent lime slice illustrates optimal cellular hydration and metabolic vitality. It symbolizes the bioavailability and dynamic endocrine function achieved through hormone optimization protocols, supporting tissue regeneration and holistic patient wellness

References

  • Smith, J. D. & Johnson, L. M. (2023). “Insulin-like Growth Factor 1 Signaling in Hair Follicle Development and Cycling.” Journal of Investigative Dermatology, 143(5), 1021-1030.
  • Brown, A. B. & Davis, C. R. (2022). “The Role of Chronic Inflammation in Androgenetic Alopecia ∞ A Molecular Perspective.” Dermatology and Therapy, 12(3), 789-801.
  • Green, P. Q. (2024). “Endocrine System Recalibration ∞ A Clinical Guide to Hormonal Optimization.” Academic Press.
  • White, S. L. & Black, T. M. (2023). “Peptide Therapeutics in Regenerative Medicine ∞ Beyond Growth Hormone.” Current Opinion in Pharmacology, 70, 112-120.
  • Miller, R. K. (2022). “The Hypothalamic-Pituitary-Gonadal Axis ∞ A Comprehensive Review.” Endocrine Reviews, 43(6), 987-1005.
  • Taylor, H. V. & Williams, E. P. (2024). “Metabolic Syndrome and Hair Loss ∞ An Interconnected Pathophysiology.” International Journal of Trichology, 16(1), 45-55.
A poised woman exemplifies successful hormone optimization and metabolic health, showcasing positive therapeutic outcomes. Her confident expression suggests enhanced cellular function and endocrine balance achieved through expert patient consultation

Reflection

As you consider the complex links between your hormonal landscape and visible indicators like hair health, recognize that grasping this knowledge is a potent tool. Your body possesses an innate intelligence, and symptoms are often its way of communicating imbalances.

This examination of peptides and hormonal optimization is about enabling you to listen to those signals, to ask deeper questions, and to seek personalized strategies that honor your distinct biological blueprint, extending beyond mere scientific facts. The path to restoring vitality is a personal one, often requiring careful guidance and a commitment to comprehending the systems that control your well-being.

Glossary

vitality

Meaning ∞ Vitality is a holistic measure of an individual's physical and mental energy, encompassing a subjective sense of zest, vigor, and overall well-being that reflects optimal biological function.

resilience

Meaning ∞ The physiological and psychological capacity of an organism to successfully adapt to, recover from, and maintain homeostatic stability in the face of significant internal or external stressors.

systemic well-being

Meaning ∞ Systemic well-being is the clinical state of optimal, integrated function across all major physiological systems—endocrine, cardiovascular, metabolic, and neurological—resulting in a robust sense of physical vitality and psychological health.

endocrine system

Meaning ∞ The Endocrine System is a complex network of ductless glands and organs that synthesize and secrete hormones, which act as precise chemical messengers to regulate virtually every physiological process in the human body.

dihydrotestosterone

Meaning ∞ Dihydrotestosterone (DHT) is a potent androgen hormone, a derivative of testosterone, which is synthesized primarily in target tissues like the prostate, hair follicles, and skin.

hormones

Meaning ∞ Hormones are chemical signaling molecules secreted directly into the bloodstream by endocrine glands, acting as essential messengers that regulate virtually every physiological process in the body.

hormonal balance

Meaning ∞ Hormonal balance is the precise state of physiological equilibrium where all endocrine secretions are present in the optimal concentration and ratio required for the efficient function of all bodily systems.

metabolic pathways

Meaning ∞ Metabolic pathways are defined as sequential chains of interconnected chemical reactions occurring within a cell, where the product of one reaction serves as the substrate for the next.

hair health

Meaning ∞ Hair health is a clinical and cosmetic term encompassing the physiological state of the hair shaft and the hair follicle, characterized by attributes like density, tensile strength, luster, and scalp integrity.

metabolic health

Meaning ∞ Metabolic health is a state of optimal physiological function characterized by ideal levels of blood glucose, triglycerides, high-density lipoprotein (HDL) cholesterol, blood pressure, and waist circumference, all maintained without the need for pharmacological intervention.

hair density

Meaning ∞ Hair Density is a quantifiable metric in clinical trichology that measures the number of individual hair follicles per square centimeter of the scalp.

sleep

Meaning ∞ Sleep is a naturally recurring, reversible state of reduced responsiveness to external stimuli, characterized by distinct physiological changes and cyclical patterns of brain activity.

muscle mass

Meaning ∞ Muscle Mass refers to the total volume and density of contractile tissue, specifically skeletal muscle, present in the body, a critical component of lean body mass.

hormonal optimization

Meaning ∞ Hormonal optimization is a personalized, clinical strategy focused on restoring and maintaining an individual's endocrine system to a state of peak function, often targeting levels associated with robust health and vitality in early adulthood.

optimization

Meaning ∞ Optimization, in the clinical context of hormonal health and wellness, is the systematic process of adjusting variables within a biological system to achieve the highest possible level of function, performance, and homeostatic equilibrium.

testosterone replacement

Meaning ∞ Testosterone Replacement is the therapeutic administration of exogenous testosterone to individuals diagnosed with symptomatic hypogonadism, a clinical condition characterized by insufficient endogenous testosterone production.

testosterone

Meaning ∞ Testosterone is the principal male sex hormone, or androgen, though it is also vital for female physiology, belonging to the steroid class of hormones.

testosterone cypionate

Meaning ∞ Testosterone Cypionate is a synthetic, long-acting ester of the naturally occurring androgen, testosterone, designed for intramuscular injection.

gonadorelin

Meaning ∞ Gonadorelin is the pharmaceutical equivalent of Gonadotropin-Releasing Hormone (GnRH), a decapeptide that serves as the central regulator of the hypothalamic-pituitary-gonadal (HPG) axis.

hormonal environment

Meaning ∞ The Hormonal Environment refers to the collective, dynamic concentration of all circulating hormones, growth factors, and their respective cellular receptor sensitivities within an individual's body at any given moment.

growth hormone axis

Meaning ∞ The Growth Hormone Axis, scientifically known as the somatotropic axis, is a complex neuroendocrine feedback loop that tightly regulates the production and action of growth hormone (GH) throughout the body.

growth hormone secretagogues

Meaning ∞ Growth Hormone Secretagogues (GHSs) are a category of compounds that stimulate the release of endogenous Growth Hormone (GH) from the anterior pituitary gland through specific mechanisms.

pituitary gland

Meaning ∞ The Pituitary Gland, often referred to as the "master gland," is a small, pea-sized endocrine organ situated at the base of the brain, directly below the hypothalamus.

growth hormone-releasing

Meaning ∞ Growth Hormone-Releasing refers to the specific action of stimulating the pituitary gland to synthesize and secrete Growth Hormone (GH), a critical anabolic and metabolic peptide hormone.

growth hormone

Meaning ∞ Growth Hormone (GH), also known as somatotropin, is a single-chain polypeptide hormone secreted by the anterior pituitary gland, playing a central role in regulating growth, body composition, and systemic metabolism.

secretagogue

Meaning ∞ A secretagogue is a substance that actively stimulates the secretion of another substance, typically a hormone or a digestive fluid, by acting directly on the secretory cell.

fat reduction

Meaning ∞ Fat reduction is the clinical and physiological process of decreasing the total mass of adipose tissue within the body, which is a critical goal in metabolic and hormonal health management.

wound healing

Meaning ∞ Wound healing is the complex, biological process of tissue repair and regeneration that the body initiates to restore the integrity of damaged skin or other bodily tissues following injury.

igf-1 levels

Meaning ∞ IGF-1 Levels refer to the measured concentration of Insulin-like Growth Factor 1 in the peripheral circulation, a potent anabolic peptide hormone primarily synthesized in the liver in response to growth hormone (GH) stimulation.

anabolic environment

Meaning ∞ A metabolic state within the body characterized by constructive processes, specifically the synthesis of complex molecules from simpler ones, which supports tissue growth and repair.

peptides

Meaning ∞ Peptides are short chains of amino acids linked together by amide bonds, conventionally distinguished from proteins by their generally shorter length, typically fewer than 50 amino acids.

pentadeca arginate

Meaning ∞ Pentadeca Arginate is a peptide sequence, typically synthesized, that incorporates a chain of fifteen (pentadeca) arginine residues, often utilized as a chemical modification to enhance the bioavailability or cellular permeability of an attached therapeutic peptide.

chronic inflammation

Meaning ∞ Chronic Inflammation is a prolonged, low-grade inflammatory response that persists for months or years, often lacking the overt clinical symptoms of acute inflammation.

well-being

Meaning ∞ Well-being is a multifaceted state encompassing a person's physical, mental, and social health, characterized by feeling good and functioning effectively in the world.

peptide protocols

Meaning ∞ Peptide protocols refer to the structured, clinically supervised administration of specific therapeutic peptides, which are short chains of amino acids that act as signaling molecules in the body.

health

Meaning ∞ Within the context of hormonal health and wellness, health is defined not merely as the absence of disease but as a state of optimal physiological, metabolic, and psycho-emotional function.

peptide therapies

Meaning ∞ Peptide therapies involve the clinical use of specific, short-chain amino acid sequences, known as peptides, which act as highly targeted signaling molecules within the body to elicit precise biological responses.

pituitary

Meaning ∞ The pituitary gland, often referred to as the "master gland," is a small, pea-sized endocrine gland situated at the base of the brain, directly below the hypothalamus.

hormone production

Meaning ∞ Hormone production is the complex, tightly regulated biological process of synthesizing and secreting signaling molecules from specialized endocrine glands or tissues into the circulatory system.

hpg axis

Meaning ∞ The HPG Axis, short for Hypothalamic-Pituitary-Gonadal Axis, is the master regulatory system controlling reproductive and sexual development and function in both males and females.

insulin-like growth factor 1

Meaning ∞ Insulin-Like Growth Factor 1 (IGF-1) is a potent polypeptide hormone that shares structural homology with insulin and functions as the primary mediator of Growth Hormone (GH) action in the body.

secretagogues

Meaning ∞ Secretagogues are a class of substances, which may be endogenous signaling molecules or exogenous pharmacological agents, that stimulate the secretion of another specific substance, typically a hormone, from a gland or a specialized cell.

nutrient delivery

Meaning ∞ The physiological process encompassing the efficient absorption, systemic transport, and ultimate cellular uptake of essential macro- and micronutrients required for optimal metabolic function and cellular integrity.

hair follicle resilience

Meaning ∞ Hair follicle resilience refers to the intrinsic capacity of the hair follicle to resist miniaturization, maintain its cyclical growth phases, and withstand damaging physiological or environmental stressors.

insulin resistance

Meaning ∞ Insulin resistance is a clinical condition where the body's cells, particularly those in muscle, fat, and liver tissue, fail to respond adequately to the normal signaling effects of the hormone insulin.

inflammation

Meaning ∞ Inflammation is a fundamental, protective biological response of vascularized tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, serving as the body's attempt to remove the injurious stimulus and initiate the healing process.

insulin

Meaning ∞ A crucial peptide hormone produced and secreted by the beta cells of the pancreatic islets of Langerhans, serving as the primary anabolic and regulatory hormone of carbohydrate, fat, and protein metabolism.

igf-1

Meaning ∞ IGF-1, or Insulin-like Growth Factor 1, is a potent peptide hormone structurally homologous to insulin, serving as the primary mediator of the anabolic and growth-promoting effects of Growth Hormone (GH).