Fundamentals
The Body as an Integrated System
You feel it in your energy, your sleep, your ability to recover. A subtle shift, or perhaps a dramatic one, has occurred. The sense of vitality that once felt innate now seems conditional, elusive. These experiences are valid data points. They are your body’s method of communicating a change in its internal landscape.
Understanding this landscape is the first step toward reclaiming your function. The human body operates as a deeply interconnected system, a biological network where no single component acts in isolation. Hormones and peptides are the primary messengers in this network, orchestrating a constant dialogue between cells, tissues, and organs.
A therapeutic protocol, such as one involving Testosterone Replacement Therapy (TRT) or Growth Hormone (GH) peptides, introduces a specific, powerful message into this system. The efficacy of that message, however, depends entirely on the environment it enters. Lifestyle interventions ∞ the choices you make regarding nutrition, movement, sleep, and stress ∞ are the architects of this environment. They determine whether the body is primed to listen and respond to the therapeutic signals being introduced.
Consider the endocrine system as the body’s internal communication grid. Hormones travel through the bloodstream, carrying instructions that regulate everything from metabolism and mood to immune function and libido. Peptides, which are small chains of amino acids, often act as more targeted messengers, signaling for specific actions like tissue repair or the release of other hormones.
When a protocol like weekly Testosterone Cypionate injections is initiated, the goal is to restore a key signal that has diminished. The injected testosterone is the message. The body’s vast network of cellular receptors must be able to receive it. Lifestyle choices directly influence the sensitivity and availability of these receptors.
A body burdened by chronic inflammation, poor metabolic health, or inadequate rest will have a communication grid filled with static, making it difficult for the therapeutic message to be heard and acted upon.
The Four Pillars of the Biological Environment
To truly comprehend how lifestyle modulates peptide protocol outcomes, we must examine the four foundational pillars that construct your body’s internal environment. Each pillar has a profound and direct impact on the endocrine system, capable of either amplifying or diminishing the effects of a given therapy.
These are not separate variables to be optimized in isolation; they are interwoven elements of a single, dynamic system. Your daily habits are, in a very real sense, a form of biological programming that sets the stage for any clinical intervention.
Nutrition the Fuel and the Information
Food provides the raw materials for cellular function and hormonal production. A diet rich in nutrient-dense whole foods, lean proteins, complex carbohydrates, and healthy fats supplies the essential building blocks for hormones like testosterone and for the repair processes stimulated by growth hormone peptides.
For instance, cholesterol is a precursor to all steroid hormones, including testosterone. Adequate protein intake is necessary for muscle protein synthesis, a process that TRT and peptides like Ipamorelin / CJC-1295 are designed to enhance. Beyond building blocks, food is also information. High-sugar, processed foods can lead to chronic inflammation and insulin resistance.
Insulin is a master metabolic hormone, and when its signaling is impaired, it creates a cascade of dysfunction that can blunt the effectiveness of other hormonal signals. A therapeutic dose of Tesamorelin intended to reduce visceral fat will be less effective in an environment of high insulin, as the body is already in a state of fat storage.
Movement the Catalyst for Cellular Response
Physical activity, particularly resistance training, is a potent stimulus for hormonal signaling. The mechanical stress of lifting weights creates a demand for repair and growth. This demand sensitizes muscle cells to anabolic signals. When you administer TRT, the testosterone looks for androgen receptors to bind to.
Resistance exercise has been shown to increase the density of these receptors in muscle tissue. This means that the same dose of testosterone can have a more powerful effect in a body that is regularly challenged with resistance training. Similarly, high-intensity exercise is a natural stimulus for growth hormone release.
When you use a GH secretagogue like Sermorelin, which encourages your pituitary to release its own GH, the effect is synergistic with the natural pulse created by exercise. The protocol and the lifestyle intervention speak the same language, sending a coordinated and amplified message for adaptation and repair.
Your daily habits are a form of biological programming that sets the stage for any clinical intervention.
Sleep the Foundation for Repair and Rhythmic Function
The majority of the body’s repair processes and hormonal regulation occurs during sleep. The pituitary gland releases its largest pulse of growth hormone during the deep, slow-wave stages of sleep. Chronic sleep deprivation disrupts this natural rhythm, leading to elevated levels of the stress hormone cortisol and reduced GH output.
Introducing a GH peptide protocol into a sleep-deprived system is like trying to plant a garden in barren soil. The peptide may signal for GH release, but it is fighting against a powerful opposing tide of high cortisol and a blunted natural rhythm.
For protocols involving peptides like Sermorelin or Ipamorelin, which are often administered before bed to work with the body’s natural GH pulse, high-quality sleep is a non-negotiable prerequisite for success. Restorative sleep allows the body to lower inflammation, consolidate memory, and fully engage in the anabolic processes that these therapies are meant to support.
Stress Management the Guardian of Hormonal Balance
The body’s stress response is governed by the Hypothalamic-Pituitary-Adrenal (HPA) axis. Chronic psychological or physiological stress leads to the sustained elevation of cortisol. Cortisol is a catabolic hormone; its primary function in a stress state is to break down tissues (like muscle) to provide energy.
This is in direct opposition to the anabolic, or building, signals of testosterone and growth hormone. A state of high chronic stress can effectively suppress the Hypothalamic-Pituitary-Gonadal (HPG) axis, which controls testosterone production. It can also increase the production of somatostatin, a hormone that inhibits the release of growth hormone.
Therefore, a person undergoing TRT or GH peptide therapy while experiencing chronic, unmanaged stress is creating a biological tug-of-war. The therapeutic protocol is pushing the accelerator for growth and repair, while cortisol is slamming on the brakes. Practices such as mindfulness, meditation, or even dedicated time in nature can help regulate the HPA axis, lower cortisol, and create a more permissive environment for anabolic therapies to work.
Intermediate
Synergistic Mechanisms Lifestyle and Protocol Integration
At an intermediate level of understanding, we move from the general concept of lifestyle influence to the specific biochemical and physiological mechanisms through which this synergy operates. A peptide protocol is a precise biochemical instruction. Lifestyle choices dictate the efficiency with which that instruction is translated into a tangible physiological outcome.
The relationship is not merely additive; it is multiplicative. An optimized lifestyle does not just add to the benefits of a protocol; it multiplies its efficacy by preparing the body’s signaling pathways and cellular machinery for the intended action.
For example, a standard protocol for a male on TRT might involve weekly injections of Testosterone Cypionate, supplemented with Gonadorelin to maintain testicular function and an aromatase inhibitor like Anastrozole to manage estrogen conversion. The testosterone injection provides the primary anabolic and androgenic signal.
However, the fate of that testosterone molecule is heavily influenced by the individual’s metabolic health. In a state of high inflammation and insulin resistance, often driven by a diet high in processed foods and a sedentary lifestyle, the activity of the aromatase enzyme is upregulated.
This means a larger percentage of the administered testosterone will be converted to estradiol, potentially leading to unwanted side effects and a blunted therapeutic response. A nutrient-dense, anti-inflammatory diet and regular exercise help to regulate aromatase activity, ensuring more of the testosterone can bind to androgen receptors and perform its intended function.
Nutritional Modulation of Hormonal Pathways
The interaction between nutrition and hormonal therapy is a complex interplay of substrate availability, enzymatic regulation, and cellular sensitivity. A well-formulated nutritional strategy can directly enhance the outcomes of specific protocols.
How Does Diet Impact TRT and Estrogen Management?
The management of estrogen is a critical component of successful TRT for both men and women. The aromatase enzyme, which converts testosterone to estrogen, is highly expressed in adipose (fat) tissue. Therefore, an individual with a higher body fat percentage will naturally have higher aromatase activity.
A nutritional plan focused on creating a caloric deficit to reduce body fat will, in turn, reduce the total aromatase load in the body. This can decrease the required dose of Anastrozole, an aromatase inhibitor, reducing potential side effects associated with overly suppressed estrogen. Furthermore, certain micronutrients play a role in hormone metabolism.
Zinc is a crucial mineral for testosterone production and immune function, while cruciferous vegetables (like broccoli and cauliflower) contain compounds such as indole-3-carbinol, which can support healthy estrogen metabolism in the liver.
Optimizing the Anabolic Window for GH Peptides
Growth hormone peptides like Sermorelin and the combination of Ipamorelin / CJC-1295 work by stimulating the pituitary gland to release GH. GH then travels to the liver, where it stimulates the production of Insulin-Like Growth Factor 1 (IGF-1), which is responsible for many of the anabolic effects of growth hormone.
This entire process is exquisitely sensitive to blood glucose and insulin levels. High circulating insulin can blunt the pituitary’s GH release. For this reason, these peptides are most effective when administered in a fasted state, typically before bed or post-workout.
A nutritional strategy that emphasizes stable blood sugar, avoiding large spikes in insulin from refined carbohydrates, creates a more favorable baseline environment for these peptides to work. Administering Ipamorelin after a high-sugar meal is biochemically counterproductive, as the resulting insulin surge will directly inhibit the desired GH pulse. A diet based on the principles of glycemic control is therefore fundamental to maximizing the return on investment from a GH peptide protocol.
A therapeutic protocol introduces a specific signal; the body’s internal environment, shaped by lifestyle, determines the clarity and impact of that signal’s reception.
The table below illustrates how different nutritional approaches can either support or hinder the efficacy of common peptide and hormone protocols.
| Protocol | Supportive Nutritional Strategy | Counterproductive Nutritional Strategy | Underlying Mechanism |
|---|---|---|---|
| Testosterone Replacement Therapy (TRT) |
High-protein, nutrient-dense diet with healthy fats. Focus on zinc, magnesium, and vitamin D. Caloric balance to maintain healthy body composition. |
High-sugar, processed food diet. Excessive alcohol consumption. Chronic caloric surplus leading to obesity. |
Provides precursors for steroidogenesis. Reduces adipose tissue, thereby lowering aromatase activity and inflammation. Supports receptor sensitivity. |
| Growth Hormone Peptides (e.g. Ipamorelin/CJC-1295) |
Diet focused on glycemic control. Timed carbohydrate intake around workouts. Adequate protein for IGF-1 synthesis. Fasting periods. |
Frequent consumption of high-glycemic carbohydrates. Eating large meals immediately before peptide administration. |
Low insulin levels are required for optimal GH release from the pituitary. High insulin blunts the GH pulse, reducing the protocol’s effectiveness. |
| Metabolic Peptides (e.g. Tesamorelin) |
Moderate caloric deficit with sufficient protein to preserve lean mass. High-fiber diet to improve satiety and gut health. |
Caloric surplus. Diet high in saturated and trans fats, which promotes visceral fat storage. |
The peptide’s function is to target and reduce visceral adipose tissue. A supportive diet creates the necessary energy deficit for fat mobilization to occur. |
Exercise as a Signal Amplifier
Exercise is not just about burning calories; it is a powerful signaling event that prepares the body for growth and adaptation. Different types of exercise send different signals, which can be strategically paired with specific protocols.
- Resistance Training ∞ This form of exercise is the single most potent lifestyle intervention for amplifying the effects of anabolic protocols like TRT. The mechanical tension placed on muscle fibers during a lift triggers a cascade of signaling pathways, most notably increasing the number and sensitivity of androgen receptors within the muscle cells. This creates more “docking stations” for the testosterone provided by TRT to bind to and initiate muscle protein synthesis. For a man on a Post-TRT protocol using agents like Clomid or Gonadorelin to restart natural production, resistance training provides a crucial endogenous signal to the testes to produce testosterone.
- High-Intensity Interval Training (HIIT) ∞ HIIT is a powerful stimulus for the natural release of growth hormone. The metabolic stress created by short bursts of all-out effort sends a strong signal to the pituitary. When combined with a GH secretagogue protocol, HIIT can create a more robust and prolonged elevation of GH and subsequent IGF-1 levels. This is particularly beneficial for protocols aimed at fat loss and improved metabolic health.
- Endurance and Cardiovascular Exercise ∞ Steady-state cardiovascular exercise improves mitochondrial density and efficiency, enhancing the body’s overall metabolic engine. It also improves insulin sensitivity, which, as discussed, is critical for the efficacy of GH peptides. For individuals on TRT, improved cardiovascular health ensures efficient delivery of hormones and nutrients to target tissues throughout the body. A study on older, obese men with hypogonadism found that while adding TRT to a lifestyle intervention didn’t improve physical function more than the lifestyle changes alone, it did help preserve muscle mass and bone density during weight loss, showcasing a protective, synergistic effect.
The Chronobiology of Sleep and Stress
The timing and quality of rest are as critical as the interventions themselves. The endocrine system operates on a 24-hour circadian clock, and disrupting this clock has profound consequences for protocol efficacy.
What Is the Cortisol-Growth Hormone Opposition?
Sleep deprivation and chronic stress lead to a dysregulated HPA axis and elevated cortisol. Cortisol and Growth Hormone have an antagonistic relationship. Cortisol promotes the breakdown of tissue (catabolism), while GH promotes the building of tissue (anabolism). Furthermore, cortisol stimulates the release of somatostatin, a hormone that directly inhibits the pituitary’s release of GH.
A study investigating GH secretion found that the normal nocturnal surge of GH disappeared entirely during sleep deprivation. This means that even if a peptide like Sermorelin is administered, its effect will be severely blunted by the inhibitory environment created by high cortisol and somatostatin. Effective stress management techniques and prioritizing 7-9 hours of quality sleep per night are essential to lower cortisol, reduce somatostatin, and allow the GH axis to function optimally.
The following list outlines the cascading effects of poor sleep and high stress on hormonal protocols:
- Increased Cortisol ∞ Directly suppresses the HPG (testosterone) and GH axes. Promotes a catabolic state.
- Elevated Somatostatin ∞ Actively blocks the release of growth hormone from the pituitary gland, counteracting GH peptide signals.
- Reduced Insulin Sensitivity ∞ High cortisol can induce a state of temporary insulin resistance, impairing nutrient uptake and blunting GH release.
- Increased Aromatase Activity ∞ Stress and inflammation can increase the conversion of testosterone to estrogen.
- Impaired Recovery ∞ The body’s ability to repair tissue, a primary goal of many peptide protocols, is severely compromised without adequate sleep.
By understanding these intermediate mechanisms, it becomes clear that lifestyle is not an adjunct to peptide therapy. It is the very foundation upon which the therapy is built. An informed patient, in partnership with their clinician, can strategically manipulate these lifestyle pillars to create a biological environment that is primed for success, transforming a standard protocol into a highly personalized and effective intervention.
Academic
Molecular Interplay at the Cellular Level
An academic exploration of this topic requires a descent into the cellular and molecular machinery that governs the response to hormonal and peptide signals. The efficacy of a protocol is ultimately determined at the level of receptor binding, intracellular signaling cascades, and gene transcription. Lifestyle interventions exert their influence by modulating these fundamental processes.
We will focus specifically on the intersection of the Growth Hormone/Insulin-Like Growth Factor-1 (GH/IGF-1) axis with key cellular signaling pathways influenced by exercise and nutrition, providing a mechanistic basis for the observed synergistic effects.
The GH/IGF-1 axis is a cornerstone of somatic growth, metabolism, and tissue repair. Growth Hormone Secretagogues (GHS), such as Ipamorelin, or Growth Hormone Releasing Hormone (GHRH) analogs like Sermorelin and CJC-1295, initiate this cascade by stimulating pulsatile GH release from the anterior pituitary.
Circulating GH then acts on hepatocytes (liver cells) to stimulate the synthesis and secretion of IGF-1. While endocrine IGF-1 circulates systemically, a crucial component of tissue repair is the production of local, autocrine/paracrine IGF-1 within tissues like skeletal muscle, a process heavily influenced by mechanical loading (exercise).
The physiological outcome of a GH peptide protocol is therefore dependent on the pituitary’s responsiveness to the secretagogue, the liver’s capacity for IGF-1 production, and the target tissue’s sensitivity to both GH and IGF-1. Lifestyle factors are potent modulators of all three stages.
The Role of Resistance Exercise in Modulating the GH/IGF-1 Axis
Resistance exercise is a powerful physiological stimulus that perturbs cellular homeostasis in skeletal muscle, initiating a complex adaptive response. This response is mediated by several key signaling pathways that directly intersect with the GH/IGF-1 axis.
Mechanotransduction and Local IGF-1 Isoforms
The mechanical strain of resistance exercise triggers a process called mechanotransduction. This process activates satellite cells, the resident stem cells of skeletal muscle, and stimulates the expression of local IGF-1 isoforms within the muscle fiber itself, particularly Mechano-Growth Factor (MGF), an IGF-1 splice variant.
This local, autocrine/paracrine IGF-1 is critical for initiating muscle protein synthesis. When a systemic GH peptide protocol elevates circulating GH and endocrine IGF-1, it encounters a muscle environment that has been primed by exercise. The exercise-induced increase in local MGF and the sensitization of IGF-1 receptors create a cellular environment that is highly receptive to the anabolic signals delivered by the protocol.
Research indicates that the hypertrophic effects of exercise on skeletal muscle may be mediated more by this local IGF-1 activity than by systemic, circulating levels, highlighting the indispensable role of mechanical loading.
AMPK and mTOR the Metabolic Switch
At the heart of the cell’s energy-sensing and growth-regulating network are two key protein kinases ∞ AMP-activated protein kinase (AMPK) and the mechanistic target of rapamycin (mTOR). These two pathways have a generally reciprocal relationship.
- AMPK is the cell’s energy sensor. It is activated during times of energy deficit, such as during exercise or fasting. AMPK activation promotes catabolic processes like fatty acid oxidation and inhibits anabolic processes, including mTOR signaling, to conserve energy.
- mTOR is the master regulator of cell growth and proliferation. It is activated by growth factors (like IGF-1) and amino acids (from protein intake). mTOR activation is essential for initiating the translation phase of muscle protein synthesis.
Resistance exercise creates a unique biphasic response. During the exercise bout itself, AMPK is activated to meet the immediate energy demand. Following the workout, provided there is adequate nutritional intake (particularly protein), AMPK activity subsides, and the mTOR pathway is strongly activated.
The IGF-1 stimulated by a peptide protocol is a potent activator of the mTOR pathway via the PI3K/Akt signaling cascade. Therefore, timing peptide administration and post-workout nutrition is critical. A post-workout protein shake provides the amino acid substrate (leucine being a key mTOR activator) while the elevated IGF-1 from the protocol provides the growth factor signal, leading to a powerful, coordinated activation of mTOR and a maximal stimulus for muscle hypertrophy.
The efficacy of a peptide protocol is ultimately determined at the level of receptor binding, intracellular signaling cascades, and gene transcription.
The table below details the molecular responses to resistance exercise and how they synergize with a GH peptide protocol.
| Cellular Event | Triggered By Resistance Exercise | Influence of GH Peptide Protocol | Synergistic Molecular Outcome |
|---|---|---|---|
| Receptor Sensitivity |
Upregulation of IGF-1 receptor density and sensitivity on myocyte membranes. |
Increases the systemic concentration of the ligand (GH and endocrine IGF-1). |
Enhanced signal reception and downstream activation of intracellular pathways like PI3K/Akt. |
| Local Growth Factor Expression |
Stimulates expression of local IGF-1 isoforms (e.g. Mechano-Growth Factor) via mechanotransduction. |
Provides a systemic anabolic environment that supports the action of local growth factors. |
Amplified activation of satellite cells and initiation of muscle repair and hypertrophy. |
| Intracellular Signaling |
Creates the metabolic conditions (post-exercise) for potent mTOR pathway activation. |
IGF-1 provides a primary upstream signal to activate the PI3K/Akt/mTOR pathway. |
Maximal phosphorylation and activation of mTORC1, leading to robust initiation of muscle protein synthesis. |
| Gene Transcription |
Activates transcription factors related to muscle adaptation and protein synthesis. |
GH and IGF-1 can influence the expression of genes related to growth and metabolism. |
Coordinated expression of the genetic blueprint required for long-term muscle adaptation and hypertrophy. |
Metabolic Health as the Permissive Factor
The state of an individual’s metabolic health, particularly their degree of insulin sensitivity or resistance, forms the systemic backdrop against which all hormonal signals are interpreted. Chronic hyperinsulinemia and insulin resistance, often resulting from poor diet and inactivity, create a state of low-grade systemic inflammation and disrupt multiple endocrine axes.
How Does Insulin Resistance Impair Protocol Efficacy?
Insulin resistance has several deleterious effects on peptide and hormone protocol outcomes. First, as previously mentioned, high levels of circulating insulin directly suppress GH secretion from the pituitary, a phenomenon that can counteract the primary mechanism of GHS peptides. Second, insulin resistance is associated with increased levels of inflammatory cytokines like TNF-α and IL-6.
These cytokines can interfere with hormone receptor function, effectively “deafening” the cells to the signals from TRT or peptide therapies. A study on postmenopausal women found that while combination HRT could worsen insulin resistance and increase C-reactive protein (an inflammatory marker), other studies suggest estrogen therapy can improve insulin sensitivity, indicating a complex relationship that is likely modulated by baseline metabolic health and the specific hormone regimen used.
Third, the metabolic inflexibility characteristic of insulin resistance means the body is less efficient at switching between fuel sources. This can impair the fat-loss effects of protocols using peptides like Tesamorelin or the body-recomposition effects of TRT and GH peptides.
Lifestyle interventions that improve insulin sensitivity ∞ such as a low-glycemic diet, regular exercise, and adequate sleep ∞ are therefore not merely beneficial; they are a prerequisite for restoring the integrity of the body’s signaling environment, allowing therapeutic protocols to function as intended.
In conclusion, from a molecular and academic perspective, lifestyle interventions are not soft recommendations. They are potent modulators of the very cellular machinery that peptide protocols are designed to target. They prepare the receptors, prime the signaling cascades, and create the metabolic and inflammatory environment that ultimately dictates whether a therapeutic signal is received with clarity and translated into a robust physiological adaptation, or lost in the noise of systemic dysfunction.
References
- Davidson, J.R. et al. “Growth hormone and cortisol secretion in relation to sleep and wakefulness.” Journal of Psychiatry & Neuroscience, vol. 16, no. 2, 1991, pp. 96-102.
- Frystyk, Jan. “Exercise and the growth hormone-insulin-like growth factor axis.” Medicine and Science in Sports and Exercise, vol. 42, no. 1, 2010, pp. 58-66.
- Hoffman, Jay R. and Nicholas A. Ratamess. “The Role of Growth Hormone and IGF-1 in the Body’s Response to Exercise.” ACE Certified, Aug. 2021.
- Jiang, Y. et al. “New Meta-Analysis Shows That Hormone Therapy Can Significantly Reduce Insulin Resistance.” The Menopause Society, Press Release, 10 Sept. 2024.
- LITROS trial investigators. “Testosterone Replacement Therapy Added to Intensive Lifestyle Intervention in Older Men With Obesity and Hypogonadism.” The Journal of Clinical Endocrinology & Metabolism, vol. 106, no. 3, 2021, pp. e1096-e1110.
- Nindl, Bradley C. et al. “Growth Hormone and Insulin-like Growth Factor-I Molecular Weight Isoform Responses to Resistance Exercise Are Sex-Dependent.” Frontiers in Physiology, vol. 11, 2020, p. 952.
- Sutton, John R. and John D. Young. “Growth Hormone/Insulin-Like Growth Factor-I Axis in Exercise and Sport.” Growth Hormone & IGF Research, vol. 7, 1997, pp. S7-S12.
- Walsh, J. P. et al. “The effects of hormone replacement therapy on insulin resistance in postmenopausal women.” Clinical Endocrinology, vol. 62, no. 6, 2005, pp. 653-8.
- Lowcountry Male. “Peptides Combined With Diet And Exercise.” Accessed July 24, 2025.
- Healthline. “10 Ways to Boost Human Growth Hormone (HGH) Naturally.” Accessed July 24, 2025.
Reflection
Calibrating Your Internal System
The information presented here provides a map of the biological territory you inhabit. It details the intricate connections between your daily choices and the powerful signals introduced by clinical protocols. This knowledge is the starting point. The true work begins with self-observation, with learning to read the signals your own body is sending.
How does a night of poor sleep affect your recovery? What is the felt difference in your energy when your nutrition is aligned with your goals? This process of introspection transforms abstract scientific concepts into a lived, practical reality.
Each person’s system is unique, with its own history, genetic predispositions, and sensitivities. The data from your lab work provides one set of coordinates. Your subjective experience provides another. The path forward involves integrating these two sets of data, using the principles discussed as a guide to experiment and discover what truly calibrates your individual system.
This journey is about moving beyond passively receiving a treatment and actively participating in the cultivation of your own health. The ultimate goal is to create an internal environment where your body is not fighting against itself, but is instead primed and ready to heal, adapt, and function with renewed vitality.
Glossary
testosterone replacement therapy
lifestyle interventions
metabolic health
peptide protocol
biological programming that sets
growth hormone peptides
muscle protein synthesis
insulin resistance
resistance training
resistance exercise
growth hormone
lifestyle intervention
sermorelin
hpa axis
signaling pathways
aromatase activity
nutritional strategy
growth factor
protein synthesis
insulin sensitivity
growth hormone secretagogues
igf-1 axis
skeletal muscle
local igf-1 isoforms
