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ORIGINAL ARTICLE
Year : 2013  |  Volume : 13  |  Issue : 1  |  Page : 27-33

Serum cortisol and testosterone alterations following exercise in normoxic and hypoxic conditions in trained young men


1 Clinical Fellow of Nephrology, Internist, Parsa Hospital, Tehran, Iran
2 Department of Exercise Physiology, Islamic Azad University, Central Branch, Tehran, Iran

Date of Web Publication28-May-2013

Correspondence Address:
Suzan Sanavi
Clinical Fellow of Nephrology, Internist, Parsa Hospital, Ansari St, Valiye-Asr Ave, Postal code: 1334954161, Tehran
Iran
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1319-6308.112222

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  Abstract 

Background: Adaptive processes to high-altitude-induced hypoxia imply complex modifications in several endocrine and metabolic functions. The purpose of this study was to determine the effects of submaximal aerobic activity on serum cortisol and testosterone levels in normoxia and hypoxic conditions in trained young men. Materials and Methods: The study population consisted of 17 healthy men, aged 20-25 years, with mean maximal oxygen uptake and BMI of 48.6 ± 3.96 ml/kg/min and 21.6 ± 0.91 kg/m 2 , respectively. They performed 30-min running on treadmill, at the intensity of 70% of maximal heart rate, in normoxia and at simulated altitudes of 2750, 3250 and 3750 m. The sessions were interfered with 72-h resting intervals. Blood samples for hormonal assays were obtained before exercise and at 0 h and 1 h post-exercise. Data analyses were performed, using the SPSS version 16. Results: Serum cortisol had not significant changes following exercise under normoxic and hypoxic conditions. Post-exercise total testosterone showed decreased levels in hypoxic conditions comparing to normoxia which was significant at 1 h post-exercise. Decreased level of post-exercise free testosterone was also observed at simulated altitudes above 3000 m that was significant at 0 h post-exercise values and accompanied with raising pattern during 1 h later. Conclusion: It seems that hormonal responses following exercise at high-altitude tend towards maintaining homeostasis. However, more accurate conclusion requires further investigations with repeated measurements.

Keywords: Aerobic activity, altitude, cortisol, hypoxia, testosterone


How to cite this article:
Sanavi S, Mirsepasi M. Serum cortisol and testosterone alterations following exercise in normoxic and hypoxic conditions in trained young men. Saudi J Sports Med 2013;13:27-33

How to cite this URL:
Sanavi S, Mirsepasi M. Serum cortisol and testosterone alterations following exercise in normoxic and hypoxic conditions in trained young men. Saudi J Sports Med [serial online] 2013 [cited 2023 Jun 5];13:27-33. Available from: https://www.sjosm.org/text.asp?2013/13/1/27/112222


  Introduction Top


High altitude has not been defined precisely but most individuals develop clinical, physiological and biochemical changes above 3000 m height. There are individual variations and some people develop signs and symptoms of high-altitude sickness at heights as low as 2000 m above sea. [1] Some investigators have arbitrarily defined the high altitude as the elevation above 2500 m. [2] High-altitude exposure as a physiological model of hypoxia induces complex metabolic and endocrine adaptations which have not been clearly understood. It seems that the simulation of high altitude, improves individuals' aerobic capacities. Therefore, for training purposes, athletes prefer to use commercial devices providing the hypoxic environment which may change hormonal balance due to increased physiological stress. [3] In addition to hypoxic conditions, physical activity per se, as a stressful condition can alter the serum cortisol and testosterone levels. [4],[5],[6],[7] For the first time, Adlercreutz proposed the ratio between serum testosterone and cortisol as an indicator of activity load in 1986 [8] that could also be useful for monitoring fitness, overtraining and overstrain in strenuous exercise. The exact pattern of this ratio in response to physical activity changes is not clear so that reduced, increased and constant values has been reported following exercise. [8],[9],[10] Hormonal responses in hypoxic conditions may be more intensive and even unpredictable, comparing to normoxia, due to reduced maximal oxygen consumption and increased work load. [11],[12],[13] There are few studies on endocrine function in hypoxic conditions which have different interpretations. This study was conducted to compare the effects of submaximal aerobic exercise on serum cortisol, total testosterone and free testosterone in normoxia and different hypoxic conditions in trained young men.


  Materials and Methods Top


Subjects

After announcing call among university students in Tehran and explaining the study purposes, 17 eligible trained men, aged 20-25 year, who had signed consent form were enrolled the study. The subjects were otherwise healthy, non-smokers and without history of medical disorders in prior 6 months. They had regular practice at least 3 days per week during the past two years. All data, including demographic information and medical history, were collected by a questionnaire.

Exercise program

Five days before initiation of the study, aerobic power of the participants was measured, using Bruce test on treadmill, and thereafter they met in the first exercise session. [14] The exercise program was composed of four sessions of aerobic exercise which were interspaced with 72-h resting intervals and to avoid misleading results, the order of sessions was chosen on a random basis. Each session consisted of 30-min running on treadmill with the intensity of 70% of maximal heart rate (MHR) in normoxia [fraction of inspired oxygen (FiO2) 0.21 equivalent to the height of 1200 m above sea] and 3 different levels of normobaric hypoxic conditions (FiO2 0.13, 0.14, and 0.15 equivalent to 3750, 3250, and 2750 m heights, provided by an Australia made inhaler device the "Go2 altitude". [15] MHR was calculated by the equation of 208 - (0.7 × age). [16] The participants were asked to refrain from drinking caffeine and alcohol at nights before sampling days. The sampling procedures were performed for each participant in the same conditions, to neutralize the effect of circadian rhythm. Indeed, each session was started and finished in a definite time which was similar for each participant during the study. All protocols were approved by the Graduate Council of Faculty of Physical Education and Sport Sciences of Islamic Azad University.

Blood sampling and hormone analysis

Blood samples were taken before, immediately (0 h) and 1 h after each exercise session. Serum cortisol, total testosterone and free testosterone were measured for each participant and then ratios between total testosterone/free testosterone and cortisol were calculated. Serum cortisol and free testosterone were assayed by ELISA (Enzyme Linked Immuno Sorbent Assay) method using "dbc" kits (made in Canada) with a sensitivity of 0.5 mcg/dl and 0.17 pg/ ml, respectively. Total testosterone was measured by chemiluminescense method using "Autobio" kits (made in Australia) with sensitivity of 0.2 ng/ml.

Statistical analysis

All analyses were performed using the SPSS version 16 statistical software (SPSS Inc., Chicago, IL). Mean ± SD (Standard Deviation) were presented for quantitative variables. The normality of the study variables was tested by One-Sample Kolmogorov-Smirnov (KS) test. In addition skewness and kurtosis measures have been used to confirm the results of the test due to paucity of samples; since in this case the KS test tends toward rejecting the null hypothesis of normal distribution. Absolute values less than 2 and 3, respectively, for skewness and kurtosis considered as normality. For serum cortisol and free testosterone, the normality of data was rejected and hence logarithmic transformations were applied on the data. Linear mixed model analyses were used to assess the effect of repeated measurements within four sessions of exercises. Repeated measures within session constructed the covariance structure in these analyses. Based on Akaike's Information Criterion (AIC), the first-order autoregressive was determined as the optimal covariance structure. Restricted Maximum Likelihood (REML) procedure was used to fit the model. To address the hypotheses of the study several analyses were performed for each dependent variable. Sidak post hoc test was used to follow the results of mixed models in significant cases (Adjusted for pair wise comparisons). P-values less than 0.05 were considered as significant. [17]


  Results Top


Physical characteristics of the participants have been shown in [Table 1]. Tables 2-6 show the mean values of serum cortisol, total testosterone and free testosterone and the ratios between total testosterone/free testosterone and cortisol in pre- and post-exercise (at 0 h and 1 h later) phases.
Table 1: Physical characteristics of the participants

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Serum cortisol levels had not significant changes in relation to training session, hypoxic conditions (F (8, 56) = 1.584, P = .151) and post-exercise values (P > 0.05, [Table 2])
Table 2: Pre- and post-exercise cortisol levels (mcg/dl)

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For serum total testosterone, there was significant decline [Table 3] within measures totally evaluated in the sessions (F (8, 56) = 8.964, P < .001). Furthermore, based on the results of the post hoc test for hypoxic sessions, significant differences were observed between pre- and post-exercise values (P 2750 = 0.001, P 3250 = 0.002 and P 3750 < 0.046 at 0 h and P < 0.001, P = 0.002 and P = 0.062 at 1 h later, respectively). There was a significant difference among sessions at 1 h after training (P < 0.05, [Table 3]). The post hoc test showed significant differences between normoxia and two hypoxic conditions (P 2750 = 0.001, P 3250 = 0.007).
Table 3: Pre- and post-exercise total testosterone levels (ng/ml)

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Significant difference was found in serum free testosterone levels totally evaluated in the sessions (F (8, 60) = 3.766, P = 0.001). There were also significant differences between normoxia and hypoxic conditions at 2750 and 3250 m (P < 0.05, [Table 4]). The post hoc test showed a significant difference between 0 h and 1 h post-exercise values for free testosterone in both normoxia and hypoxia 3250 (P = 0.031 and P = 0.007, respectively). In addition, significant differences between pre- and 1 h post- exercise values were obtained in hypoxia 2750 and normoxia (P = 0.016 and P = 0.029).
Table 4: Pre- and post-exercise free testosterone levels (pg/ml)

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There were significant differences for post-exercise values (at 0 h and 1 h) among sessions (P < 0.05, [Table 4]). Moreover, the post hoc test revealed a significant difference between 0 h values in normoxia and hypoxia 3750 , 3250 (P = 0.022, 0.02) and 1 h values in normoxia and hypoxia 2750 (P = 0.019).

No significant difference was seen for serum total testosterone to cortisol ratio in different conditions (F (8, 54) = 0.595, P = 0.778) and between pre- and post-exercise values (P > 0.05, [Table 5]).
Table 5: Pre- and post-exercise serum total testosterone to cortisol ratio

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A significant difference was found in serum free testosterone to cortisol ratio within in the sessions (F (8, 53) = 0.877, P = 0.542), however, the separate evaluation of the values showed no significant difference within measurements in all sessions (P > 0.05, [Table 6]).
Table 6: Pre- and post-exercise serum free testosterone to cortisol ratio

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There were significant differences among sessions for 0 h post-exercise values (P < 0.05, [Table 6]). In addition, the post hoc test revealed a significant difference between hypoxia 2750 and hypoxia 3750 (P = 0.031).


  Discussion Top


This study showed increased serum cortisol levels, immediately following exercise, in three different hypoxic conditions (particularly at 3750 m height) comparing to normoxia, however, these elevations were not significant and hypoxia per se did not change the exercise-induced cortisol responses. This finding is compatible with some researches [3],[18],[19] but comes into conflict with some others. [20],[21],[22],[23] The confliction may be attributed to the levels of altitude or hypoxia, assumption of natural or simulated height and exercise intensity in different investigations. Indeed, increased serum cortisol levels have been reported in studies at 3500-5200 m heights, while at higher altitude, serum cortisol levels had no difference with the sea levels. [18] Moreover; exercise variables including type, intensity, volume, duration and rest periods and previous training status of subjects can influence on serum cortisol. [24],[25],[26] High-altitude induced hypoxia can increase serum cortisol, but the definite level of height has not been defined. In our study, serum cortisol showed decreased levels, immediately after the exercise. Most studies that have observed an increase in serum cortisol levels following the exercise had a high intensity. Usually, when the intensity of exercise exceeds a threshold (60% of maximal oxygen consumption or 75% of MHR), serum cortisol will increase. [27],[28] In this situation which is accompanied with reduced muscle glycogen, the body supplies energy requirements from triacylglycerol break down and free fatty acid production by increasing serum cortisol concentrations. [29] The acute exposure to reduced partial pressure of oxygen at high-altitude decreases arterial oxygen saturation, stimulates the sympathoadrenal system, and provokes shifts in substrate metabolism. In addition, hypoxia can stimulate adrenocorticotropic hormone (ACTH) secretion. [26] However; Bouissou et al., showed that hypoxia may act through increasing adrenal glands sensitivity to ACTH. [19]

With respect to our findings, we suggest more researches in different hypoxic conditions with repeated measurements of hypothalamic-pituitary-target gland hormones, due to their diurnal variations and pulsatory nature of secretion.

Androgens, as anabolic hormones, influence on the growth and muscular development. They also have a well recognized function in maintenance of skeleton and by an enhancing action on protein synthesis contribute in muscle fiber repair and hypertrophy during exercise. In maximal exercise, muscle glycogen is of particular importance as muscle energy substrate, and exercise increases the ability of muscle tissue to synthesize and store glycogen. Recent animal studies demonstrated that this ability is dependent on adequate testosterone levels and thus the observed rise in testosterone in exercise may be important in utilization and replenishment of muscle glycogen. [30] Testosterone may in addition influence carbohydrate metabolism in muscle by increasing the availability of creatine phosphate. The raised androgen levels may further be associated with the aggressiveness and drive necessary to perform maximal exercise and may also contribute to the feeling of well being experienced by athletes who are approaching peak fitness. [30] The present study revealed decreased serum total testosterone concentrations at 0 h and 1 h post-exercise blood samples in three hypoxic conditions. However, the reduction was significant only at 1 h samples comparing to similar blood levels in normoxia. This finding is compatible with other researches. [18],[21],[31],[32],[33],[34],[35] It has been reported that high-altitude induced overproduction of serum nitric oxide can inhibit steroid hormone synthesis. [36],[37] However; there are also reports of increased serum total testosterone concentrations following low intensity exercises. [38],[39] It seems that, exercise intensity has a major influence on post-exercise total testosterone levels. [40],[41] On the other hand, we found increased serum free testosterone levels, immediately following exercise, at 2750 m height and to a lesser degree in normoxia. With increasing the heights (≥ 3000 m), similar blood samples primarily showed decreased levels accompanied with raising pattern during 1 h later. This raising pattern maintains normal anabolic action of sex hormone following exercise in hypoxic conditions. Perhaps repeated measurements may be necessary for better understanding of post-exercise response during 1 h later in both normoxia and hypoxic conditions.

Based on the above findings, it seems that ratio between free testosterone and cortisol (FTCR) may be more impressive as an indicator of work load and hormonal training status of athletes, however, data regarding endocrine adaptations are scanty and discrepant, likely reflecting different experimental models and wide relative ranges of altitudes, and generally investigating the short-term endocrine response only. Increased amount of the FTCR in recovery phase of activity may be a response for maintaining homeostasis. This reveals the importance of repeated post-exercise measurements for future researches. Imbalances in homeostasis usually occur in submaximal exercise at very high altitudes (> 5000 m) but may be observed in low altitudes, if the severity and duration of activity is enough. Inadequate recovery period delays full restoration of energy reserves and leads to fatigue and exhaustion. [25]


  Conclusion Top


Exercise under hypoxic conditions comparing to normoxia results in greater physical work-load. It is recommended that athletes who intend to improve their aerobic capacities at simulated high-altitudes, have adequate resting following exercises to prevent exhaustion. On the other hand, since the profiles of the anabolic-catabolic hormone concentrations measured are indicators of the performance level of athletes, it is better to follow them by repeated assays during altitude training to optimize training program for individual athletes. Further investigations in different degrees of hypoxia with larger sample sizes are also suggested.

 
  References Top

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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]


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