Explaining All Muscle & Bone Building Hormones (NO BS)

Myokines, produced by muscle fibers during contraction, act as local growth hormones. Follistatin, a key myokine, deactivates myostatin, a protein that limits muscle growth. Intense, progressive training is essential for maximal myokine release, leading to significant local muscle response. Unlike systemic hormones, myokines are exercise dose-dependent and cannot be bought or shortcutted, emphasizing the importance of intelligent programming over junk volume.

IGF-1 is critical for muscle building, especially the local IGF-1 produced within muscles in response to damage. Local IGF-1 activates M2, triggering protein synthesis and, crucially, satellite cell activation. Satellite cells donate new nuclei to muscle fibers, permanently expanding growth capacity. Mechanical tension, not metabolic stress, is the primary trigger for local IGF-1 production, making heavy lifting more effective than high-rep cable exercises for activating this growth pathway.

Insulin's main role in muscle growth is preventing breakdown by allowing glucose and amino acids to enter muscle cells and shutting down catabolic pathways. It also potentiates IGF-1 effects. While insulin spikes are beneficial post-workout, chronic hyperinsulinemia from frequent meals and processed carbs leads to insulin resistance, hindering nutrient partitioning to muscle. Maintaining insulin sensitivity through leanness and quality food is crucial for effective muscle growth.

Testosterone promotes muscle growth by binding to androgen receptors, activating genes for muscle protein synthesis. However, the density and sensitivity of these receptors, which are genetically determined, vary greatly. High testosterone levels are less effective with poor receptors. Testosterone also increases myionuclear number, similar to IGF-1 activation, contributing to long-term growth capacity and enhancing neuromuscular drive. For most natural lifters, optimizing training intensity and insulin sensitivity is more critical than increasing testosterone levels unless they are clinically low.

Crushing estrogen levels is detrimental to muscle growth. Estrogen reduces muscle damage, speeds up recovery, and dramatically improves insulin sensitivity, ensuring nutrients are partitioned to muscle. Optimal estrogen levels are vital for strength, recovery, and nutrient partitioning for both men and women. The industry's promotion of aromatase inhibitors for men often backfires, leading to decreased strength, joint pain, slow recovery, and poor insulin sensitivity.

DHT binds to androgen receptors more strongly than testosterone, increasing neural drive and enhancing motor unit recruitment. This translates to more force generation, heavier lifts, and greater mechanical tension, which triggers more IGF-1 and myokine release. DHT also contributes to intramuscular density, leading to a harder, more separated physique. Blocking DHT with drugs like finasteride can negatively impact lifts, muscle quality, and potentially sexual function, and is generally not recommended unless genetically prone to baldness.

Administered alone, Growth Hormone has minimal direct impact on muscle gain. Its primary roles are increasing liver IGF-1 production, mobilizing fat for fuel, and supporting connective tissue. GH's real power lies in its synergy with testosterone and insulin. For natural lifters, the body produces significant GH pulses during deep sleep and intense training. Prioritizing 8 hours of sleep and genuine training intensity is more effective than obsessing over GH supplements.

Thyroid hormones (T3 and T4) are regulatory, not anabolic, but crucial for metabolic rate and protein turnover. Imbalances can halt muscle growth and fat loss. Aggressive calorie restriction can downregulate thyroid function, while chronic overfeeding can cause reverse T3 to rise, blocking active T3. Standard TSH testing is often inadequate; comprehensive testing (TSH, free T3, free T4, reverse T3, antibodies) is recommended for individuals struggling with progress despite proper training, nutrition, and sleep. Addressing thyroid issues, whether through reverse dieting, managing inflammation, or hormone replacement, is fundamental for overall hormonal balance and muscle growth.