Strongman Physiology - Episode 7: Growth Hormone and IGF-1

1. Growth hormone is not only about growth

Growth hormone, or GH, is intuitively associated with childhood and height, but its role in adults is much broader. GH contributes to metabolic regulation, tissue remodeling and adaptive processes. A major portion of its effects is mediated through IGF-1, produced mainly by the liver but also locally in many tissues.

In Strongman, this axis matters because it helps shape the physiological environment in which tissues recover and remodel, but it should not be reduced to a simple equation such as “more GH equals more strength.”

2. What is the GH–IGF-1 axis?

The hypothalamus controls GH secretion through a balance between GHRH and somatostatin, while ghrelin can provide an additional stimulatory signal. The pituitary releases GH in pulses, and GH acts on the liver and other tissues to promote IGF-1 production.

IGF-1 carries an important part of the growth and repair signal. The axis is regulated through negative feedback, allowing the system to remain dynamic and responsive.

3. Why is GH secretion pulsatile?

GH is not secreted at a constant rate. Levels rise and fall in pulses, with a major pulse often associated with deep sleep. Physical activity, fasting, metabolic stress and other factors can alter these pulses.

This is why a single GH blood test has little value for describing everyday physiologic secretion. IGF-1 is more stable and can provide more useful information about axis activity, but it also should not be interpreted in isolation.

4. Sleep: one of the major physiological drivers of GH

Deep sleep favors GH release, while sleep restriction and fragmentation can alter the profile. For strength athletes, this matters because sleep simultaneously supports neuromuscular recovery, metabolic control and endocrine function.

Saying that “GH is produced at night” is too simplistic. Secretion is linked to sleep architecture and the timing of particular sleep stages, not merely to darkness.

5. GH, IGF-1 and protein synthesis

IGF-1 can activate signaling pathways involved in cellular growth and metabolism, including the PI3K–AKT–mTOR pathway. In muscle, these processes are relevant to remodeling and adaptation to mechanical and metabolic stimuli.

However, a Strongman's hypertrophy is not produced by a single molecule. Mechanical tension, protein intake, energy availability, recovery and training programming remain central.

6. GH and muscle: where the story starts and ends

GH has important metabolic actions, while IGF-1 participates in anabolic and repair-related processes. Still, the relationship between circulating GH or IGF-1 and strength gain is much more complex than supplement marketing and “muscle hormone” narratives suggest.

A normal physiologic level supports the biological environment required for adaptation. A high level does not automatically guarantee better performance in a yoke, deadlift or stone carry.

7. The metabolic effects of GH

GH is not exclusively anabolic. It can increase fatty-acid mobilization and, in some contexts, reduce glucose utilization. It therefore plays an important role in fuel distribution, especially between meals and in selected physiologic stress states.

For a Strongman, this metabolic component helps explain why hormones do not “build muscle” in an energetic vacuum. Substrate availability and overall energy balance remain fundamental.

8. GH and IGF-1 in bone tissue

The GH–IGF-1 axis contributes to bone growth and remodeling. In adults, bone remains metabolically active, with formation and resorption continuously balanced.

In a sport with very high mechanical loads, skeletal health depends on the interaction of loading, nutrition, vitamin D, calcium, sex hormones, GH–IGF-1 and overall health.

9. Connective tissues: tendons, cartilage and collagen

GH and IGF-1 influence processes involved in extracellular-matrix synthesis and remodeling. This is relevant to connective tissues that transfer force from muscle to the skeleton.

But tendon adaptation is slow, tissue-specific and distinct from muscle hypertrophy. An athlete cannot assume that changing one hormonal marker will automatically create stronger tendons in a short time.

10. Why does this matter in Strongman?

Strongman combines muscle mass, maximal strength, repeated effort and tolerance of unusual loads. Muscle and connective tissues therefore need to adapt together.

The GH–IGF-1 axis is one piece of that adaptation system. It cannot be isolated from inflammation, mechanotransduction, sex hormones, insulin, nutrition and recovery.

11. GH after training

Exercise can acutely alter GH secretion, and the magnitude of the response depends on exercise type, volume, rest periods, muscle mass involved and other session characteristics.

A post-exercise rise is a temporary physiologic response, not proof that the session was automatically more anabolic over the long term.

12. GH, IGF-1 and muscle soreness

It is tempting to link soreness with a large hormonal response. In reality, delayed-onset muscle soreness is shaped by microdamage, inflammation, sensitization and novelty of the stimulus, not by GH or IGF-1 alone.

A Strongman can have a marked endocrine response without necessarily experiencing more soreness, and vice versa.

13. GH and low energy availability

Fasting and low energy availability can raise GH while lowering IGF-1. This apparent paradox shows that hormones operate in networks and cannot be interpreted by looking at whether one value moves up or down.

During an aggressive diet, a higher GH level does not mean the body is in an optimal anabolic state. Low energy availability can restrict exactly the processes required for growth and recovery.

14. Insulin and IGF-1

Insulin and IGF-1 interact in the regulation of metabolism and growth. Nutrition, carbohydrate intake and energy status can influence the availability of these signals.

The practical message for athletes is simple: there is no endocrine axis that exists independently of food. Diet changes the hormonal environment in which adaptation takes place.

15. GH and body composition

Adipose tissue, particularly excess visceral adiposity, is associated with altered GH secretion. Obesity can reduce GH pulse amplitude, while weight loss may improve secretion in some contexts.

Again, metabolic health and performance are not separate domains. Body composition can influence endocrine function, while endocrine function can influence metabolism.

16. GH and age

GH secretion and IGF-1 levels generally decline with age. This phenomenon is often called somatopause and is part of normal aging physiology.

However, the age-related decline is not automatically a disease and does not justify using growth hormone as an anti-aging or performance method.

17. What does adult GH deficiency mean?

Adult GH deficiency is a distinct medical condition, not simply normal hormonal variation between athletes. It can be associated with changes in body composition, exercise capacity and quality of life, but diagnosis requires endocrine assessment and specific testing.

A low IGF-1 can raise suspicion, but it is not sufficient by itself to establish the diagnosis.

18. Exogenous GH: why it is not the same as physiology

Exogenous growth hormone produces exposures that do not simply reproduce the body's natural pulses. Effects and risks depend on dose, duration, medical context and other interventions.

Non-medical use can be associated with fluid retention, altered glucose metabolism and other adverse effects. It is not a benign intervention and should not be presented as a simple recovery accelerator.

19. GH, IGF-1 and absolute strength

A Strongman's absolute strength depends heavily on muscle mass, muscle architecture, leverage, technique and the nervous system's capacity to produce force. GH and IGF-1 may contribute to the biological environment in which these qualities are built, but they do not replace them.

This helps explain why two athletes with apparently similar endocrine parameters can have very different performances.

20. GH and recovery

GH participates in tissue remodeling and may influence post-exercise metabolic balance. But recovery in Strongman is not controlled by a single hormone.

Adequate sleep, energy intake, protein, carbohydrate, hydration and control of training volume matter far more for day-to-day recovery than trying to chase a particular hormonal pulse.

21. What can impair the GH–IGF-1 axis?

Fragmented sleep, obesity, some systemic illnesses, nutritional deficiency and endocrine disorders can alter the axis. GH and IGF-1 can change in different directions, which makes interpretation more complex.

In sport, a period of fatigue should not automatically become an endocrine diagnosis. Common causes and the broader context should be considered first.

22. How should IGF-1 be viewed on a laboratory test?

IGF-1 is more stable than GH and can be useful in evaluating the axis, but the result must be interpreted according to age and laboratory reference ranges. Liver function, nutrition, acute illness and other conditions can affect the level.

Correct interpretation belongs to the clinical context. A single IGF-1 value should not be converted into a conclusion about an athlete's performance potential.

23. The classic mistake: “more hormone means more adaptation”

Sports endocrinology is full of nonlinear relationships. A healthy endocrine system is not trying to maximize every hormone at every moment; it is trying to match signaling to context. Sometimes a hormone rises because energy is scarce, not because the body has better conditions for growth.

For Strongman, high-quality adaptation comes from coordination between training stimuli, fuel, endocrine signals and recovery.

24. GH–IGF-1 during competition week

In the week before a competition, changes in sleep, stress, nutrition and training volume can alter the endocrine environment. There is no single ideal hormonal profile for every situation.

The priority is to protect sleep and nutrition routines, reduce unnecessary fatigue and enter competition with as little physiologic disruption as possible.

25. Conclusion: GH and IGF-1 are infrastructure, not magic

The growth-hormone and IGF-1 axis is an important part of adult physiology. It influences metabolism, tissue remodeling and the interaction between sleep, energy and adaptation.

For Strongman, the main lesson is that this axis helps create part of the biological environment in which performance can be built, but it cannot replace training, nutrition or recovery. A hormone does not lift the stone. The whole organism does.

Selected bibliography

1. Melmed S, Bronstein MD, Chanson P, et al. A Consensus on the Diagnosis and Treatment of Acromegaly Complications. Endocrine Reviews.

2. Giustina A, Barkan A, Casanueva FF, et al. Criteria for cure of acromegaly: a consensus statement. Journal of Clinical Endocrinology & Metabolism.

3. Clemmons DR. Role of IGF-I in skeletal muscle mass maintenance. Trends in Endocrinology and Metabolism.

4. Juul A. Serum levels of insulin-like growth factor I and its binding proteins in health and disease. Growth Hormone & IGF Research.

5. Van Cauter E, Plat L. Physiology of growth hormone secretion during sleep. Journal of Pediatrics.

6. Voss JD, Weng HY, et al. Exercise, growth hormone and IGF-1: interactions between training, metabolism and adaptation. Exercise endocrinology literature.

7. Endocrine Society clinical guidance and peer-reviewed literature on adult growth hormone deficiency, IGF-1 interpretation and acromegaly.

Editorial note: this article is educational. Diagnosis of growth hormone deficiency, acromegaly or other endocrine disorders requires medical evaluation and specific testing. Non-medical use of growth hormone carries risks and should not be treated as a simple performance strategy.