5 ways insulin can affect fertility
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Hormone hierarchy

In a previous post I wrote about how insulin affects fertility and here I want to discuss how cortisol, as the pair for insulin in the hormone hierarchy, also affects fertility.

What is cortisol?

Cortisol is a hormone involved in the stress response. It’s produced by a complex network known as the hypothalamic pituitary adrenal (HPA) axis.

The HPA axis includes your hypothalamus and pituitary gland, both of which are in your brain. It also includes your adrenal glands, which sit atop your kidneys.

To make cortisol, your hypothalamus sends a signal to your pituitary gland. It does this by releasing a substance called corticotropin-releasing hormone (CRH).

CRH stimulates your pituitary gland to

send another hormone into your bloodstream. That hormone is called adrenocorticotropic hormone (ACTH).

ACTH travels through your bloodstream to your kidneys and cues the adrenal glands to produce cortisol. Once the adrenals have produced enough cortisol, the hypothalamus stops releasing CRH.

HPA axis
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It’s a complex and sensitive feedback loop, and it has profound effects on your body, mind, and sleep.

Causes of stress

Fight or flight is the major stress response in humans. It is regulated by the para sympathetic nervous system through a feedback mechanism. Our default status, the one we are expected to be in the vast majority of the time is the homeostasis aka ‘rest and digest ‘ or ‘feed and breed’.

Stress response can be activated by any of our senses, sight, sound, smell, taste and touch.

Aside from trauma, day to day activities can also elicit the stress response including;

  • Diet, including animal protein, refined sugars, salt and caffeine
  • High intensity exercise
  • Insufficient sleep
  • The bosses footsteps coming towards you
  • Overwork
  • Financial difficulties
  • Relationship difficulties
  • Infertility
  • Health concerns
  • Excessive demands

5 ways fertility is affected

The chart above shows the hierarchy relationship between cortisol and reproductive hormones. The gold standard for measuring cortisol is a salvia rather than a blood test but either way it can be operating at a sub clinical level and still have an impact on your fertility.

5 of these affects are;

  • Chronic stress
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Acute stress occurs in response to an immediate alert. In the normal course of events the perceived danger associated with that alert goes away and the body reverts to normal homeostatsis, i.e you relax. Chronic stress occurs over time as a result of multiple alerts where the relax mode is not reset. This causes cortisol levels to remain high and can eventually lead to burnout. For as long as we are outside ‘feed and breed’ mode getting pregnant can be difficult.




  • Impaired sleep

Poor sleep can increase the production of cortisol.

Did you ever notice how men (generally) sleep on the side of the bed closest to the door, and will even swap sides when travelling? This is a caveman leftover from being between the potential oncoming predator and their more vulnerable partner and offspring!

Sleep is when we are most vulnerable and if we are stressed, sleep can feel too ‘unsafe’ to rest easy.

tired and wired
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So stress affects our sleep. Poor sleep increases cortisol. Cortisol is a fat storage hormone. Yep – poor sleep makes us fat.



  • Inflammation


As a natural response to an alert, the body can increase inflammation to counter any injury. But because the stress response cannot differentiate between a threat and a perceived threat it may raise inflammation unnecessarily, multiple times per day. Without the all important ‘off’ switch, inflammation can remain elevated for as long as the alert response is switched on. So when there is chronic stress there is often chronic, low grade inflammation which accelerates the aging process. Inflammation can prevent embryo implantation.

  • Decreased testosterone in men

Men who sleep less than 6 hours per night have significantly smaller testicles due to lowered testosterone. In the hormone hierarchy testosterone is made downstream of cortisol. Consistently elevated cortisol can block the production of testosterone leading to low sperm count.

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  • Reduced progesterone

In women, progesterone is crucial to preparing the body for pregnancy. In the presence of stress, progesterone may be converted to cortisol instead of being made available for fertility. Progesterone is involved in regulating menstrual cycles. Brown spotting prior to a period is often an indication of low progesterone.

Optimizing your fertility

Stress is clearly a factor which should be addressed as part of your fertility journey

The entire Module 7 in the Now Baby Programme is devoted to the topic, helping to identify sources of stress and offering a range of stress management tools. Nutrition is an important input for reducing diet related stress and this is well covered in Module 1 by reducing dysglysemia  and is backed up weekly with a new and delicious meal plan designed with both fuel and fertility nourishment in mind. Week 9 looks specifically at sleep and the challenges associated with shift work and Week 6 covers all of the hormones relating to the menstrual cycle including how to address low progesterone.

So when your goal is to optimize your fertility for either a natural conception or to improve your IVF success, a holistic approach can be invaluable.

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