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Sports create many positive effects in the human cardiovascular and endocrine systems. One important part of the endocrine or hormonal system is the system of stress hormones (glucocorticoids). The name glucocorticoid comes on one hand from the important role they play in the regulation of the glucose metabolism (Glucose) and on the other hand from the place where they are produced, the cortex of the adrenal gland (Cortex suprarenalis).

The regulation of the most important glucocorticoid, cortisol, depends on a control loop (see figure 1).

Activated by stress or physical activity

The hypothalamus (region in the brain) is activated by stress or physical activity and releases a hormone called CRH (corticotrophin releasing hormone). CRH induces the production and release of ACTH (adrenocorticotrope hormone) in the pituitary (another small part in the human brain). ACTH then leads to the release of cortisol from the adrenal gland. Higher cortisol levels lead to lower CRH and ACTH levels due to a negative feedback mechanism. Thus, the hormonal system will regulate normally at a certain physiological level. Within a few minutes, this system is able to adapt cortisol levels to higher needs due to stress or physical activity. Apart from the regulation of the glucose metabolism, cortisol also leads to catabolic metabolism, which means that energy reserves are used up for the energy demands of a new situation, like running. In addition to the regulation of metabolic procedures, cortisol also has many effects on the immune system and on inflammation processes.

Higher levels of cortisol can be observed

The regulation of cortisol levels is also dependent upon the time of day. In the morning and in the afternoon, higher levels of cortisol can be observed. This is very useful for the reactivation of the human body after sleeping or an after-lunch rest.

In a pathological case of an overproduction of cortisol, a so-called Cushing Syndrome can develop. Symptoms include weight gain, weakness, depression, arterial hypertension, diabetes, reduced bone density, sleeping disorders, loss of libido, and skin alterations.

On the other hand, there is also a possibility of pathologically reduced cortisol levels, which is called Addison Syndrome. Possible symptoms include nausea, weight loss, brown skin, weakness, and low blood pressure.

The Charité – CBF and the Department of Sports Medicine of the Humboldt University have examined the hormonal systems in 8 women and 11 men during their training for the real,- BERLIN-MARATHON. In order to do so, 5 examinations were performed. The first one was 6 weeks before the marathon, the second 10 days before, and the third 2 days after the marathon. The fourth exam took place 10 days after the race, and the last one was 6 weeks after the marathon. The dates were chosen according to the different levels of training, high before and low after the marathon.

The results were very interesting.

There were no significant differences in the cortisol and ACTH levels for the periods before and well after the marathon, but there were low levels of these hormones 2 days after the marathon. The results suggest that the extreme physical stress of the marathon causes a short-term exhaustion of the ACTH-cortisol-axis. Apart from the synthesis and regulation of cortisol, the degradation of cortisol was also examined. The subjects of the study all collected their urine for 24 hours. Degradation products of cortisol were measured in the urine. For the first time it could be demonstrated that the human body tries to compensate for the lower cortisol levels after a marathon through a reduced degradation of cortisol.

In addition to testing the levels of cortisol and ACTH in the blood, the sensitivity of the ACTH-cortisol-axis was also tested. By ingesting a synthetic cortisol medication, the physiological synthesis of cortisol could be suppressed and the sensitivity of the ACTH-cortisol-axis could be shown. The results of this study present hints of a lower sensitivity during periods of more intense training. This could mean that marathon training leads to a kind of resistance against stress and that the human body is exposed to intensified cortisol action. Whether this is a positive or a negative effect has not yet been determined. In order to answer this question, further research over a longer period of time is necessary.

Other pituitary hormones were examined in this study, as well

In addition to stress hormones like cortisol or ACTH, other pituitary hormones were examined in this study, as well. No significant differences for thyroidal hormones or growth hormones could be observed. For men, lower testosterone values were found during the intense periods of training. This is one previously known effect of intensive endurance training, which could be confirmed in this study. Lower testosterone values do not seem to have any pathological impacts like loss of libido or loss of bone density.

Returning to the major focus of the study, one interesting change in the cortisol metabolism due to marathon training and a marathon race could be observed. This is not associated with any pathological changes, which were seen for example in persons with so-called over-training syndrome. The overtraining syndrome is characterised primarily by a reduced physical fitness and an unwell feeling without any actual illness. Normally, the over-training syndrome occurs during periods of intense training, which is common in professional sports. Although this disease is well known, no diagnostic procedure exists. Some studies have shown the first hints for an altered cortisol metabolism, like presented in this study.

Further information about the study can be found in the medical journal:

Clinical Endocrinology or through:

Dr. Thomas Bobbert, CharitéBerlin –

CBF, Dept. of Endocrinology, Diabetes, and Nutrition,

Hindenburgdamm 30,

12200 Berlin,

Phone: +49/30-8445-2664.

Dr. Thomas Bobbert, a young doctor at the Charité - Campus Benjamin

Franklin – in the Endocrinology, Diabetes, and Nutritional Medicine Department of Prof. Pfeiffer, already has a long career at the BERLIN-MARATHON behind him.

He started out as a spectator and fan of his father Bernd (Jubilee-Club member) at the BERLIN-MARATHON, where he stood cheering him on at the Yorck Bridges year for year, then he volunteered at the MARATHON souvenir stand and helped out at the refreshment stand of the Luise Henriette High School (Tempelhof) and in the Horst Milde bakery in Thielallee and later in Potsdamer Strasse. He then moved up to be in charge of the awards ceremony of the MARATHON and of the BERLIN-MARATHON Jubilee-Club. Now he is part of the medical team of the MARATHON.

Bobbert also was a successful athlete, becoming German Junior Champion in the 800 m for the sport club TSV Tempelhof-Mariendorf in 1994, making it to the semi-finals at the Junior World Championships in 1994, and becoming German Champion in the 4 x 800 m relay with SCC in 1996. His personal best for the 800m is 1:48,73 – but then his Achilles tendon got messed up. Together with Mark Milde (now Race Director of the real,- BERLIN-MARATHON), he was often part of the winning school team for the MINI-MARATHON, the Luise Henriette High School. His brother Peter, by the way, was the pace maker for Mizuki Noguchi for the first 10 kilometres this year.