Introduction
Cortisol is a hormone produced by the adrenal glands in response to stress. Often referred to as the "stress hormone," it plays a vital role in regulating metabolism, inflammation, blood pressure, and the body’s sleep–wake cycle. In small, short-term doses, cortisol is essential for survival, helping the body respond quickly to threats. However, when cortisol levels remain elevated due to ongoing stress, it can begin to harm rather than help, disrupting hormones, energy levels, and overall health.
Chronic Stress vs Acute Stress
Cortisol is not inherently bad. During short-term (acute) stress, it plays an important role in keeping the body alert and ready to respond. It helps mobilise energy, sharpen focus, and manage inflammation. However, when stress is ongoing (chronic), cortisol levels can stay elevated for too long, disrupting key bodily systems. This prolonged exposure can interfere with testosterone production, weaken immune function, and negatively affect mood and metabolism. The key distinction is that occasional stress is normal and even beneficial. It is long-term, unmanaged stress that leads to problems.
How Cortisol Impacts Testosterone
Competing for Resources
During times of high stress or intense physical activity, cortisol is released causing a decrease in testosterone production. The reason for this is because cortisol and testosterone are both derived from the same precursor molecule, cholesterol. Therefore, during high stress, cholesterol is used for cortisol rather than testosterone.
Inhibits the HPG Axis
Chronic high cortisol levels disrupt the hypothalamic-pituitary-gonadal (HPG) axis, which controls testosterone production. Cortisol can reduce the release of Gonadotropin-releasing hormone (GnRH) from the hypothalamus and Luteinising Hormone (LH) from the pituitary gland. These hormones are essential for stimulating testosterone production in the testes.
Increases Aromatase Activity
Elevated cortisol is often linked to increased body fat, especially visceral fat. This fat tissue contains aromatase, an enzyme that converts testosterone into oestrogen, further reducing available testosterone levels.
Blocks Testosterone's Effects
Even when testosterone is present, cortisol can interfere with its receptor binding and signalling, reducing its effectiveness. This is especially noticeable in muscle tissue, where cortisol promotes breakdown (catabolism), while testosterone promotes growth (anabolism).
Is Cortisol Important?
As with most hormones and key indicators within the body, there is a set level your body likes to be at (homeostasis). Therefore, having too high or too low cortisol levels can lead to unwanted effects. Cortisol also helps regulate your sleep-wake cycle.
Effects of High Cortisol
- High blood sugar
- Weight gain
- High blood pressure
- Stretch marks
- Muscle weakness
Effects of Low Cortisol
- Fatigue
- Unintentional weight loss
- Loss of appetite
- Low blood pressure
All of the effects mentioned are detrimental to regulating testosterone too — with weight (specifically fat) gain increasing aromatase activity (conversion of testosterone to oestrogen), and loss of appetite resulting in a lack of correct nutrition to support healthy testosterone production.
Ways to Better Regulate Cortisol
Stress Management
Implement stress-reducing techniques such as meditation, deep breathing exercises, stretching, and regular physical activity such as walking.
Sleep
Correcting your sleep by going to bed at a consistent time (even on weekends) and ensuring you are getting 7–9 hours of quality sleep a night helps to lower cortisol. Sleeping is also when your body produces the most testosterone. Read more about the male hormone cycle.
Overtraining
Exercise is known to stimulate the production of testosterone. However, overtraining to the point where your body is unable to recover effectively is seen to increase cortisol levels.
Supplements
In some cases, certain supplements may be beneficial in supporting healthy testosterone levels. Always seek the advice of your doctor or pharmacist with any medical questions you may have.
Conclusion
Cortisol plays a vital role in the body’s stress response and maintaining internal balance, but chronically elevated or suppressed levels can disrupt key processes, including testosterone production. While the relationship between cortisol and testosterone is complex, managing stress, maintaining a regular sleep schedule, and avoiding overtraining can support healthier hormone regulation. Ultimately, achieving hormonal balance is less about eliminating cortisol and more about keeping it in check — so testosterone can thrive.