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What is the Cortisol and Testosterone Relationship?

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When you are training to increase muscle mass and testosterone levels, you need every hormone on your team in order to support you on your journey.

Hormone release is one factor that controls many of our physiological adaptations that cause the changes in muscle mass and T levels. And a hormone that has a big effect on your T levels is cortisol.

But what is the cortisol and testosterone relationship? And how does this affect things?

In this article we explore how elevated stress and cortisol will blunt your muscle mass gains, and have a big impact on your T levels.

To expand on this we look at the following commonly asked questions:

  • What is cortisol?
  • How does cortisol affect your testosterone levels?
  • Stress responses
  • 5 ways to keep cortisol in check
  • Summary – The Cortisol and Testosterone Relationship

What is cortisol?

Our body is controlled by a number of systems, each working in tandem to create a state of balance, or homeostasis. When one hormone pulls in a specific direction, another must ease off in order to allow it in.

With regards to muscle mass – we can organize each of our hormones into either catabolic– your muscle mass breaks down, or anabolic– your muscle mass increases. Obviously on the journey to larger muscles we want to promote anabolism as much as possible.

Our anabolic hormones include T-Levels, insulin and growth hormone, with the former being our most anabolic hormone – whenever we are in an anabolic state we increase protein synthesis – this is great for muscle building.

Our catabolic hormones include cortisol, adrenaline and glucagon. Whenever we go catabolic our muscle protein synthesis decreases.

In order to promote muscle mass we need to focus as much as possible on elevating anabolic levels, whilst keeping catabolism at bay.

According to Weipeng [1] the role of T within the body is to maintain anabolism through the process of protein synthesis. By contrast, cortisol plays a catabolic function and is involved in the response of stress.

Cortisol is a steroid hormone secreted by the adrenal cortex of the adrenal gland. It is from the group of hormones called glucocorticoids, and as such is formed by cholesterol. It is released from the adrenal gland whenever the pituitary gland in the brain tells it to via a hormone called adrenocorticotropic hormone (ACTH).

Key Point: Cortisol is your body’s stress hormone, which can be secreted during physical or mental tension. When you produce more of it, your body lowers your T levels to keep a hormonal balance – this is known as homeostasis.

What is the relationship between Testosterone and Cortisol?

Think of testosterone and cortisol as being exact opposites- in the context of muscle building if T was the accelerator of muscle mass, C is most definitely the brake. They have very much an antagonistic relationship.

T increases allows us to decrease body fat, build muscle and keep a high libido. Excess levels of cortisol, however, do the opposite – it decreases muscle mass (via a process called gluconeogenesis), increases fat mass around the middle [2], suppresses your immune system, and decreases sexual appetite.

Almost all physiological and biochemical processes within the human body follow a circadian rhythm – cortisol and testosterone naturally increase and decrease throughout a day [1] with T being highest at night and low during the day, whereas cortisol production is low at night, rapidly rises during awakening and then gradually decreases over the course of the day [3].

This is important in planning exercise sessions as you’ll see later on.


Key Point: High levels of cortisol can cause problems such as lower muscle mass, increased fat mass, suppressed immune system, and lower libido.

How does Stress affect Testosterone?

In the grand scheme of things, our body can’t differentiate between stresses. Think of being on the Saharan planes; struggling for food, and wary of Sabre-toothed tigers lurking in the bushes. Pretty tense, right? Now compare that to being sat on exercise bike in a nice comfy gym – believe it or not, your body can’t tell the difference. From a hormonal point of view, the stress response is the same:

Increased heart rate, blood flow to the lower legs (so you can run away) and regardless of the type of stress our body always breaks down stored energy for fighting or running.

This ‘fight or flight’ response kicks in and we either manage to run away, fight it off, or die trying. Either way, after a short period of time we get to switch off our stress response and relax again.

But whether we exercise too much, or are constantly worrying about paying the mortgage – you never fully manage to switch off that response – and that’s bad- were constantly breaking stored energy down.

With this prolonged stress cortisol levels tend to rise and stay elevated- this why it is called the stress hormone.

cortisol and testosterone relationship

Key Point: Prolonged periods of stress can leave you feeling tired, and can push you from a muscle building machine into a fat storing shadow of yourself.

5 ways to keep your stress hormones in check

The more you stress, the more you move away from your muscle-building goal. In order to manage your catabolic output here are a few handy tips that you can use:

1.Regular sleep – Sleep is the main time the body restores itself

Your circadian rhythm is controlled by sleep-wake cycles so in order to keep cortisol low you need to ensure good sleep quantity and quality. Studies have found that in those who are fatigued or sleep deprived, cortisol levels increase not only in the morning, but also at nighttime too. [4]

Interestingly, in those that get 4 hours sleep instead of the recommended 8 hours, not only are cortisol levels higher, levels of leptin are too- a hormone that stimulates appetite. This means that are more likely to reach for the biscuit tin to satisfy your sugar cravings.

2. Have rest days These are critical to stop excessive over-training

If you don’t have set rest days you’ll quickly move from fatigued to over-trained, and your cortisol levels will hit the roof- this can take weeks or even months to recover from. Training in the gym is a pretty traumatic experience for your body and you have to give it time to recover. Those who have exercised themselves int an overtrained state can expect to see higher cortisol and lower anabolic levels. [5]

3. Lift heavy Lift bigger to produce more T

Training for strength is one sure fire way of increasing your muscle mass levels. Big compound lifts like deadlifts, presses and squats will boost your T levels and in turn keep cortisol low.

4. Exercise in the morning – Get your anabolic levels flying to set you up for the day

As we’ve already seen, our cortisol levels are at their highest in the morning and T is low- for that reason getting an early morning gym session in will help you to bring your T levels up high and boost muscle protein synthesis.

According to the research, a simple method of boosting your testosterone levels is to train with high intensity in the morning [6]. For even more advice on training at different times of day see our guide on Circadian Rhythm & Testosterone: Best Time to Workout.

5. Ditch the cardio  Long slow cardio is not the way to go

Instead of performing “long intensity, steady state” cardio, make sure you HIIT the gym instead. Not only will it decrease fat levels, it will boost your T and metabolic rate too.

Summary – What is the Cortisol and Testosterone Relationship?

The cortisol and testosterone relationship is not a productive one. Whilst one promotes anabolism, energy storage muscle mass gains, the other plays a catabolic function in breaking stored energy down.

When we exercise too much, or are constantly worrying about paying the mortgage – we never fully manage to switch the cortisol response off – and we hit the brake. Hard – and that’s bad for your progress.  

By ditching cortisol raising stressors- regularly having rest days, getting a good night’s sleep, and lifting heavy, we can allow testosterone to increase naturally and boost our gains.

What else can you do to boost T levels

TestoFuel is a premium T booster containing only ingredients that have been shown to work in the most rigorous studies. Including active ingredients such as oyster extract and magnesium this is the best product you can choose.

This supplement has the ability to support:

  • Muscle Growth and Strength – the golden chalice of weight lifting
  • Improved Recovery – hit the gym time and time again
  • Enhanced Energy – you’ll be able to train longer and harder to maximize results

TestoFuel is ideal for improving your performance both in and out of the gym, and helping you attain that all-important muscular physique.


  1. Weipeng, T et al. Circadian Rhythms in Exercise Performance: Implications for Hormonal and Muscular Adaptation. J Sports Sci Med. 2011 Dec; 10(4): 600–606
  2. Rubinow, DL et al. Testosterone Suppression of CRH-stimulated Cortisol in Men. Neuropsychopharmacology. 2005; 30(10): 1906–1912
  3. Raff, H et al. Pre-analytical issues for testosterone and estradiol assays. Steroids. 2008; 73(13): 1297-304
  4. Leproult R, et al. Sleep loss results in an elevation of cortisol levels the next evening. Sleep. 1997; 20: 865–870
  5. Snyder A et al. Overtraining following intensified training with normal muscle glycogen. Sports Exerc 1995; 27(7): 1063-70.
  6. Cook C.J et al. Morning based strength training improves afternoon physical performance in rugby union players. J Sci Med Sport. 2014; 17(3): 317-21.