Infrared Sauna and Growth Hormone: The Science Behind a Natural Hormonal Response

Human growth hormone is one of the most important hormones the body produces. It drives muscle protein synthesis, regulates fat metabolism, supports connective tissue repair, influences bone density and plays a central role in the cellular repair processes that underpin recovery from both exercise and the accumulated stress of daily life. It is also, from approximately the third decade of life onward, in steady decline.

The pharmaceutical industry has built an entire category of products — injectable synthetic growth hormone, growth hormone secretagogues, peptide protocols — around the desire to restore or augment growth hormone levels. These interventions are expensive, regulated, carry physiological risks and operate outside the body's own feedback systems. They are also, for competitive athletes, prohibited.

Against this backdrop, the peer-reviewed literature on sauna use and growth hormone secretion is particularly significant. Multiple studies have documented that specific sauna protocols produce acute growth hormone responses of meaningful magnitude — naturally, without pharmacological intervention, through the body's own endocrine response to heat stress. Understanding what the evidence actually shows, how it should be interpreted and what it means in practical terms is the purpose of this article.

What Growth Hormone Does and Why It Matters

Growth hormone is a peptide hormone produced by the anterior pituitary gland and released in pulsatile fashion — in bursts rather than continuously. Its secretion is regulated by the hypothalamic-pituitary axis, responding to a range of physiological stimuli including sleep, exercise, nutritional state and thermal stress.

The actions of growth hormone are mediated both directly and through insulin-like growth factor 1, which is produced in the liver in response to growth hormone signalling. The combined effects include stimulation of muscle protein synthesis and lean mass accretion, mobilisation of stored fat for use as fuel, support of collagen synthesis and connective tissue repair, enhancement of cellular repair and regeneration processes, contribution to bone density maintenance, and modulation of the immune system.

Growth hormone secretion peaks during adolescence and early adulthood and declines at a rate of approximately 15% per decade after the age of 30. By middle age, total daily growth hormone secretion is a fraction of its youthful levels. This decline contributes to the progressive changes in body composition — increased fat mass, reduced lean mass, slower recovery — that characterise ageing in the absence of intervention.

The most powerful natural stimulus for growth hormone secretion is deep slow-wave sleep. The largest daily growth hormone pulse occurs during the first ninety minutes of sleep, driven by the release of growth hormone-releasing hormone from the hypothalamus. Exercise — particularly resistance training and high-intensity intervals — is the second most potent natural stimulus. Heat stress is a third, and it is one that can be deliberately applied in a controlled and consistent manner.

The Research on Sauna and Growth Hormone

The foundational research on sauna-induced growth hormone secretion was conducted by Finnish researchers Leppäluoto and colleagues, who documented consistent and reproducible increases in serum growth hormone concentrations following repeated sauna exposures at temperatures between 80 and 100 degrees Celsius. Their work established sauna-induced hyperthermia as a legitimate and quantifiable stimulus for the hypothalamic-pituitary axis.

Subsequent research has documented the sauna-induced growth hormone response across a range of protocols, temperatures and populations, with results varying considerably based on these parameters. The reported increases in serum growth hormone following sauna exposure range from approximately two-fold to as high as sixteen-fold above baseline, depending on the specific protocol employed.

The sixteen-fold figure — a 1,600% increase — comes from research examining repeated sauna sessions conducted on consecutive days. A study documented that on the first day of repeated sauna exposures, male participants showed a sixteen-fold increase in serum growth hormone levels. This response, while striking, is not representative of the typical response to a single isolated session and should not be used in isolation as the reference point for everyday sauna use.

More representative of the effect from a single session are studies documenting increases of two to five-fold above baseline. Research published in the European Journal of Applied Physiology by Kukkonen-Harjula et al. documented haemodynamic and hormonal responses to sauna bathing, confirming consistent growth hormone elevation following heat exposure. A study examining 30-minute sessions at 73 degrees Celsius documented a five-fold increase in growth hormone levels. Two-fold increases have been documented following shorter sessions at lower temperatures.

The relationship between protocol parameters and growth hormone response is dose-dependent: higher temperatures, longer durations and multiple sessions on the same day produce greater growth hormone responses than shorter, cooler or less frequent exposures.

The Mechanism: How Heat Stress Stimulates Growth Hormone

The mechanism through which heat stress triggers growth hormone secretion is mediated by the hypothalamic-pituitary axis. When core body temperature rises during a sauna session, thermoreceptors in the hypothalamus detect the temperature change and initiate a cascade of neuroendocrine signalling.

Heat stress stimulates the hypothalamus to release growth hormone-releasing hormone — the same signalling molecule responsible for the nocturnal growth hormone pulse during sleep. This hypothalamic stimulation leads to the pulsatile secretion of growth hormone from the anterior pituitary into the circulation. The response is acute — growth hormone levels begin rising during the session and typically peak approximately thirty minutes after the session concludes, before returning toward baseline over the following one to two hours.

Several co-factors modulate the magnitude of the growth hormone response to sauna.

Fasting state. Insulin and growth hormone exist in an antagonistic relationship — when insulin levels are elevated, growth hormone secretion is suppressed. Entering a sauna session in a fasted state, or at least having avoided carbohydrate intake for two to three hours beforehand, significantly amplifies the growth hormone response. Research has documented substantially larger growth hormone spikes when sessions are conducted in a low-insulin state compared to the fed state.

Combination with exercise. Exercise is an independent growth hormone stimulus. When exercise and sauna heat stress are combined — a post-training sauna session — the growth hormone response exceeds that from either stimulus in isolation. Research examining combined exercise and heat exposure has documented peak growth hormone levels of 45 nanograms per millilitre in male participants — substantially higher than from exercise or heat alone. This additive effect is one of the physiological rationales for the post-training sauna protocol used by elite athletes.

Age. The growth hormone response to sauna is attenuated with age, consistent with the broader age-related decline in growth hormone secretion. Research has documented a 150% increase in growth hormone in men aged 31 to 46 following sauna exposure, while no significant increase was observed in men aged 49 to 66. This suggests that the sauna-induced growth hormone response is most pronounced in individuals in their third and fourth decades — the age range at which natural decline in growth hormone secretion is already underway but the pituitary remains responsive to physiological stimuli.

Session frequency and adaptation. Studies examining repeated daily sauna sessions have documented that the growth hormone response attenuates with very high frequency use. By day three of daily sessions, the spike begins to diminish. By day seven of consecutive daily use, the growth hormone response is significantly reduced. This adaptation suggests that strategic spacing of sessions — rather than daily use — optimises the hormonal response over time. Three to four sessions per week, with rest days between, preserves the growth hormone responsiveness of the hypothalamic-pituitary axis.

How This Compares to Other Natural Growth Hormone Stimuli

It is important to contextualise the sauna-induced growth hormone response relative to other natural stimuli, rather than overstate its magnitude or clinical significance.

Sleep remains the most potent natural growth hormone stimulus. The nocturnal growth hormone pulse during slow-wave sleep is three to four times larger in magnitude than the sauna-induced response and persists for several hours rather than one to two. Optimising sleep quality is the single most impactful intervention for natural growth hormone status. Notably, infrared sauna use before bed improves sleep quality through thermoregulatory cooling and parasympathetic activation — meaning sauna indirectly amplifies the nocturnal growth hormone pulse by improving the depth and duration of slow-wave sleep. This indirect effect may be as significant as the direct acute growth hormone response.

Resistance training produces a growth hormone response comparable in magnitude to sauna use. The combination of resistance training followed immediately by a post-exercise infrared sauna session compounds these independent stimuli, producing a cumulative hormonal environment significantly more conducive to recovery and adaptation than either alone.

Fasting and intermittent fasting protocols amplify growth hormone secretion by reducing insulin levels and removing its suppressive effect on pituitary growth hormone release. Combining fasting windows with sauna sessions during the fasted period is a well-documented strategy for maximising the growth hormone response.

The honest position is that the sauna-induced growth hormone response is a real, reproducible and physiologically meaningful phenomenon — but it is not equivalent to pharmacological growth hormone administration in magnitude or duration. The acute spike lasts one to two hours, not six to eight. The practical benefits for recovery and body composition accumulate over weeks and months of consistent use, not from any single session.

What makes the sauna-induced response clinically valuable is not its magnitude in isolation but its consistency, its safety, its accessibility and its compounding nature across regular sessions over time.

Prolactin, Norepinephrine and Heat Shock Proteins

Growth hormone is not the only hormonally relevant response to infrared sauna use.

Prolactin — a hormone linked to recovery, metabolism and immune function — has been documented to increase 2.3-fold in men and more than four-fold in women following infrared sauna sessions. While prolactin is most commonly associated with lactation, its broader physiological roles include immune modulation and tissue repair.

Norepinephrine — a catecholamine involved in alertness, focus and metabolic rate — increases significantly in response to the heat stress of sauna use. Research has documented substantial norepinephrine elevations during and after sessions, which is proposed as one mechanism underlying the mood enhancement and mental clarity that many sauna users report subjectively. Norepinephrine also plays a role in the mobilisation of fatty acids from adipose tissue during heat exposure.

Heat shock protein 72 increases by approximately 50% following a single sauna session. In addition to its direct cellular protective functions, heat shock protein 72 has been linked to enhanced insulin sensitivity — a metabolic benefit with implications for body composition, energy metabolism and long-term metabolic health.

The Practical Protocol for Maximising the Growth Hormone Response

Based on the peer-reviewed literature, the following evidence-based protocol maximises the natural growth hormone response to infrared sauna use:

Session timing: Post-training, within one hour of completing resistance exercise or high-intensity work. This compounds the exercise and heat stress stimuli and produces the largest combined growth hormone response.

Nutritional state: Two to three hours without carbohydrate intake before the session where possible. Low insulin levels amplify the pituitary response to heat stress.

Temperature: 43 to 50 degrees Celsius in a full spectrum infrared sauna. Adequate thermal stimulus without excessive physiological burden.

Duration: 20 minutes minimum per session. The peak growth hormone response occurs approximately thirty minutes after the session concludes, suggesting that sessions shorter than fifteen to twenty minutes may not produce sufficient thermal stimulus.

Frequency: Three to four sessions per week with rest days between. This preserves the hypothalamic-pituitary responsiveness that daily use progressively attenuates.

Sleep optimisation: Infrared sauna in the evening — two to three hours before bed — supports the thermoregulatory cooling that facilitates sleep onset and deep slow-wave sleep. This indirectly amplifies the nocturnal growth hormone pulse that represents the largest natural growth hormone stimulus available.

Conclusion

The research on sauna use and growth hormone secretion documents a real, reproducible and physiologically meaningful hormonal response to heat stress. The effect ranges from two-fold to five-fold above baseline in typical single-session protocols, with higher responses documented under specific conditions including repeated sessions, fasted state and combination with exercise.

The most significant implication is not the magnitude of any single growth hormone spike but the consistent, cumulative hormonal environment created by regular post-training infrared sauna use — one that supports muscle protein synthesis, facilitates fat metabolism, accelerates recovery and counteracts, in a modest but meaningful way, the age-related decline in growth hormone secretion that affects every individual from their third decade onward.

This is what heat stress, applied deliberately and consistently, does to the endocrine system. It is entirely natural. It is supported by peer-reviewed research. And it is built into every session in the Resonance Recovery Pod.

Sources

Leppäluoto, J., et al. Neuroendocrine effects of repeated sauna bathing. Acta Physiologica Scandinavica.

Kukkonen-Harjula, K., Oja, P., Laustiola, K., et al. (1989). Haemodynamic and hormonal responses to heat exposure in a Finnish sauna bath. European Journal of Applied Physiology, 58(5), 543–550.

Huhtaniemi, I.T., Laukkanen, J.A. (2020). Endocrine effects of sauna bath. Current Opinion in Endocrine and Metabolic Research, 11, 15–20.

Ftaiti, F., et al. (2008). Effect of hyperthermia and physical activity on circulating growth hormone. Applied Physiology, Nutrition and Metabolism, 33(5), 880–887.

Ahokas, E.K., Kyröläinen, H., Ihalainen, J.K., Hanstock, H.G. (2025). Salivary cortisol response to post-exercise infrared sauna declines over time. Temperature: Multidisciplinary Biomedical Journal.

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Laukkanen, J.A., Kunutsor, S.K. (2024). The multifaceted benefits of passive heat therapies for extending the healthspan. Temperature: Multidisciplinary Biomedical Journal.