You may have noticed a plethora of reels and posts on social media claiming cortisol “spikes” are harmful. Some warn against drinking coffee on an empty stomach or even doing certain exercises lest they “spike” your cortisol levels.As an endocrinologist, I live and breathe hormones. I can reassure you cortisol spikes are not something healthy people need to fear. In fact, cortisol rhythms – which involve some ups and some downs – are an essential part of what keeps your body well.Remind me, what is cortisol?Cortisol is an essential hormone that regulates our metabolism, immune system and cognitive/emotional processes. Cortisol regulation is complex. While cortisol release comes from your adrenal glands that sit just above your kidneys, it is under direct control by another hormone released by the pituitary gland, or “master gland” at the base of our brain. Cortisol production follows a strong daily rhythm. There is a sharp rise in cortisol levels in the first hour after waking up, called the “cortisol awakening response”.This awakening response helps you feel alert. In fact, the higher this peak, the better you can cope with the physical and mental challenges for the day ahead.A blunted cortisol awakening response (meaning they are not as high as would be ideal) is associated with poorer health.Over the course of a day, cortisol levels fall gradually and are naturally very low in the evening, designed to bring on sleep.Overlying this background rhythm there are regular cortisol pulses throughout the day, when your body is faced with challenges such as a tough workout, a stressful deadline or an infection. These cortisol rises are protective. They help you stay focused, maintain your blood pressure and release more energy when needed. So, what about coffee on an empty stomach?Cortisol levels are affected by many factors including gender, age and genetics, as well as food, exercise, stress, light and illness. Understanding the effect of a simple cup of coffee in the morning depends on the intricate and complex nature of these dynamics.Importantly, there have been no randomised controlled studies comparing coffee consumption on an empty stomach to having it after food.Certainly, coffee has been linked to a rise in cortisol levels, of up to 30% in one study, and in another even when drunk with breakfast.However, particularly in regular coffee drinkers, the effect may be negligible. Interestingly, it might be more about the timing of coffee drinking rather than whether it is consumed with or without food. In the study of habitual coffee drinkers, morning caffeine intake was not shown to meaningfully disturb the cortisol rhythm, whereas drinking coffee later in the afternoon did seem to contribute to higher cortisol levels over the course of the day.This also may have relevance to when we exercise – some studies have shown that people exercising earlier in the day have a steeper cortisol decline after waking and lower evening levels. This might mean it is easier to get to sleep.Don’t worry about ‘spikes’Rather than being concerned about cortisol “spikes”, it is sustained elevations over the course of a day that are linked to adverse health outcomes. Chronic stress states (meaning persistent and extended period of exposure to one or more stressors, such as prolonged work stress or relationship difficulties) and long-term use of cortisol-like medications (such as the corticosteroid prednisone) might be problematic. They expose the body to high cortisol levels without the natural rise and fall over a 24-hour period.Rare conditions like Cushing’s syndrome (a consequence of tumours of the pituitary or adrenal gland in most people) cause chronically elevated cortisol levels.Although some smart watches can monitor your “stress” levels, this is done indirectly via measurement of heart rate variability – not by measurement of cortisol levels.Measuring high cortisol levels requires sophisticated testing that might involve urine, saliva, as well as a variety of blood tests; so don’t be too worried about cortisol based on what your watch is telling you.If you are concerned about cortisol, you should consult your doctor. If abnormalities arise, a referral to an endocrinologist may be needed.Ann McCormack has received funding in the past for pituitary research from the St Vincent’s Clinic Foundation, Curran Foundation, IPSEN and Pfizer. She is a medical advisor for patient support group Australian Pituitary Foundation, an Endocrine Society of Australia council member (past-president), and director of The Pituitary Society.