Hormone profiles at high altitude in man

Chronic Exposure to Normobaric Hypoxia Increases Testosterone Levels and Testosterone/Cortisol Ratio in Cyclists

The aim of this study was to analyze the effects of the “live high, train low” method (LH−TL) and intermittent hypoxic training (IHT) on testosterone (T) and cortisol (C) levels in cyclists. Thirty cyclists participated in the experiment. The LH−TL group (n = 10) was exposed to normobaric hypoxia (FiO2 = 16.3%) for 11−12 h a day and trained in normoxia for 3 weeks. In the IHT group (n = 10), participants followed the IHT routine three times a week for 3 weeks in normobaric hypoxia (FiO2 = 16.3%). The control group (N; n = 10) followed the same training protocol in normoxia. The LH−TL training was found to significantly increase (p < 0.05) T levels and the testosterone/cortisol (T/C) ratio during the experiment. The area under the curve (AUC) calculated for T levels over 4 weeks was significantly (p < 0.05) higher in the LH−TL group, by 25.6%, compared to the N group. The results also indicated a significant correlation (r = 0.53; p < 0.05) between AUC for T levels over 4 weeks and ∆ values of hemoglobin (HGB) in the LH−TL group. Overall, the findings show that LH−TL training at a moderate simulated altitude contributes to an increase in T levels and T/C ratio in athletes, which is a beneficial change stimulating anabolic processes and erythropoiesis.

Association of Smoking with the Blood Concentration of 25-Hydroxy Vitamin D and Testosterone at High and Low Altitudes

Purpose

This research examined the association of cigarette smoking and altitude with the blood levels of 25-hydroxy vitamin D, testosterone and carotid artery thickness.

Patients and methods

This comparative cross-sectional study involved 37 non-smokers and 24 smokers from a high-altitude area (≥2245 m above sea level) and 40 smokers and 40 non-smokers from a low-altitude area (39–283 m above sea level). The blood testosterone level was determined spectrophotometrically, and the 25-hydroxy vitamin D concentration was measured by ELISA. The IMT of the right and left carotid arteries was determined using ultrasound imaging.

Results

Smoking notably elevated the thickness of the intima media of the right and left carotid arteries at both high and low altitudes (p ≤ 0.001). Smoking at high altitude was associated with a significant increase in the concentration of 25-hydroxy vitamin D and testosterone, while at low altitude it was associated with a significant decrease in both parameters (p ≤ 0.046).

Conclusion

These contrasting results suggest that future studies should focus on finding out if other biochemical parameters show any significant differences in smokers or/and non-smokers when they are tested at elevated height and sea-level. This indicates that dose modifications of medicines (related to alterations in vitamin D and testosterone levels) should be kept in mind while treating smokers and non-smokers at elevated height above sea level.

Levels of Follicle Stimulating Hormone (FSH), Luteinizing Hormone (LH), Testosterone and Prolactin at Moderate Altitude Inhabitant Male

BACKGROUND AND OBJECTIVE

Male fertility depends on the availability of the potent androgen called testosterone. Testosterone production is regulated by the hypothalamic anterior pituitary axis. Two anterior pituitary hormones Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH) are involved in spermatogenesis and testosterone production, respectively. Hypoxia, resulting from high altitude, may induce a change in these four hormones and may affect male fertility. This study was done to evaluate and compare the changes that occur in FSH, LH, testosterone and prolactin in males lived in moderate versus low altitude.

MATERIALS AND METHODS

This study was conducted on 300 individuals who were categorized based on the altitude of their habitat into two equal groups, namely: Inhabitants at moderate altitudes and inhabitants at low altitudes. A venous blood sample was collected from each individual to measure the levels of FSH, LH and prolactin.

RESULTS

Both LH and testosterone levels were significantly lower in high altitude inhabitants compared with low altitude inhabitants (p<0.01). The FSH level showed a significant statistical difference between two groups with a lower level in individuals living at high altitudes compared with low altitude inhabitants but on a value (p<0.05).

CONCLUSION

Moderate altitude hypoxia suppresses LH, FSH and testosterone levels as much as high altitude hypoxia does and these changes may depend on prolactin level.

Alterations of estrous cycle, 3β hydroxysteroid dehydrogenase activity and progesterone synthesis in female rats after exposure to hypobaric hypoxia

The underlying mechanism regulating hypoxia induced alteration in female steroid hormones is first time explored in this study. To understand the mechanistic approach, female Sprague- Dawley rats were exposed to acute and chronic hypobaric hypoxia (282 mm-Hg, ~7620 m, 6 hours, 3 and 7 days). Estrous cycle, body weight, plasma progesterone and estradiol levels, morphology, histology and two key steroidogenic enzymes: 3ß hydroxysteroid dehydrogenase (HSD) and 17ß HSD activity of ovary and adrenal gland were studied. A persistent diestrous phase and a significant decrease in body weight were found in chronic hypoxia groups. Histological study suggested degenerative changes in ovarian corpus luteum of 7 days chronic hypobaric hypoxia (7CHH) group and a declined percentage of adrenocortical cells in 3 days chronic hypobaric hypoxia (3CHH) and 7CHH groups. Plasma estradiol level was unaltered, but progesterone level was decreased significantly in all hypoxic groups. Ovarian 3ß HSD activity was decreased significantly with increasing days of hypoxic treatment along with a significantly low adrenal 3ß HSD activity in 7CHH. In conclusion, hypobaric hypoxia causes a state of low circulatory progesterone level in females likely due to the degenerative changes in the female ovarian and adrenal tissues together with low steroidogenic 3ß HSD enzyme activity.

Transcription regulation of NRF1 on StAR reduces testosterone synthesis in hypoxemic murine

Male chronic obstructive pulmonary disease (COPD) and sleep apnea patients are associated with serum testosterone level decline because of hypoxemia, resulting in male sexual dysfunction and lower reproductive capacity. Although testosterone replacement therapy used in clinic achieves good results, the side effects indicates that understanding the mechanism followed with targeted treatments are more meaningful. The known mechanism of Hypoxia-inducible factor-1 (HIF-1) mediated steroidogenic acute regulatory protein (StAR) repression did not well explain the reason of hypoxia induced testosterone decline. Our primary results indicated Nuclear respiratory factor 1(NRF1) might be participate in StAR transcription regulation. The study aims to identify the mechanism of the regulation of StAR by NRF1, providing an explanation for the decrease of testosterone induced by hypoxemia. Testosterone level and StAR were determined in COPD model rats, sleep apnea model mice and hypoxia rats (10%O₂). Results indicated NRF1, StAR and testosterone decreased in testis and ovary and increased in adrenal. Regulation of NRF1 expression under normoxia or hypoxia induced synchronous changes of both StAR and testosterone, indicating the decrease of NRF1 induced StAR repression in hypoxemia were the main cause of serum testosterone decline. The results were confirmed by dual-luciferase reporter assays, regulation of NRF1 synchronously altered the transcriptional activity of StAR. By ChIP, EMSA supershift, NRF1 was found to bind to the Star promoter region. Mutation assays identified two NRF1-binding sites on mouse Star promoter. These findings indicated that NRF1 positivly regulated Star transcription through directly binding to the Star promoter at -1445/-1422 and -44/-19.

Impact of high altitude on key determinants of female reproductive health: a review

Imperishable research work was done on females visiting high-altitude (HA) areas for recreational activities or job purposes as well as on female HA natives. Hypoxia at HA is an unavoidable condition that affects the determinants of female reproductive functions like, the age of menarche and menopause, whole reproductive span, hormone synthesis, and fertility. This review will emphasize whether HA hypoxia is a threat to women: residents or visitors by analyzing these proximate determinants. Delayed menarcheal and advanced menopausal age was found to shorten the reproductive span in some HA populations, whereas in some cases, menstrual cycle was also reported to be irregular. In addition, the completed fertility rate (CFR) was increased when people migrated to lower altitude. Altered stress hormones and reproductive hormones were observed in sea-level females exposed to HA. Oxidative stress (OS) at HA was also reviewed to explain the probable reasons for the observed changes in these determinants because disturbed redox homeostasis may be a connecting link, affecting the reproductive functions. In conclusion, HA hypoxia plays a crucial role on various determinants of female reproductive health and this review will be helpful for more precise study along with the probable underlying mechanisms responsible for the changes in female reproductive functions at HA.

Endocrine targets of hypoxia-inducible factors

Endocrine is an important and tightly regulated system for maintaining body homeostasis. Endocrine glands produce hormones, which are released into blood stream to guide the target cells responding to all sorts of stimulations. For maintaining body homeostasis, the secretion and activity of a particular hormone needs to be adjusted in responding to environmental challenges such as changes in nutritional status or chronic stress. Hypoxia, a status caused by reduced oxygen availability or imbalance of oxygen consumption/supply in an organ or within a cell, is a stress that affects many physiological and pathological processes. Hypoxic stress in endocrine organs is especially critical because endocrine glands control body homeostasis. Local hypoxia affects not only the particular gland but also the downstream cells/organs regulated by hormones secreted from this gland. Hypoxia-inducible factors (HIFs) are transcription factors that function as master regulators of oxygen homeostasis. Recent studies report that aberrant expression of HIFs in endocrine organs may result in the development and/or progression of diseases including diabetes, endometriosis, infertility and cancers. In this article, we will review recent findings in HIF-mediated endocrine organ dysfunction and the systemic syndromes caused by these disorders.

Alterations in different indices of skeletal health after prolonged residency at high altitude

AIMS

The aim of this study was to evaluate the effect of prolonged residency at high altitude (HA) on different indices of bone health in sea level (SL) residents staying at an altitude of 3450 m for 4 months to 1 year. The assessment of bone health parameters included multisite quantitative bone speed of sound (SOS), and markers of bone metabolism such as serum alkaline phosphatase (ALP), bone specific alkaline phosphatase (BAP), urinary deoxypyridinoline (DPD), C-terminal propeptide of type I collagen (CICP), N-telopeptide of type I collagen (NTX), and hormonal regulators such as 25-hydroxy vitamin D3 (25Vit D), intact parathyroid hormone (i-PTH), and cortisol.

RESULTS

The body weight in all the age groups was significantly lower at HA as compared to SL values. Prolonged residency at HA led to a significant decline in bone strength in terms of SOS, both at radius and phalanx. There was a significant increase in circulating Ca and ALP levels. Serum i-PTH and 25VitD levels decreased significantly. Significant decreases were also observed in CICP and BAP, bone formation markers, and serum NTX, DPD/Cr ratio, markers of bone resorption.

CONCLUSION

These observations suggest that prolonged residency under hypoxic environment is associated with a decline in both bone formation and bone resorption markers, reflecting a lower bone turnover at HA.

Effects of high-altitude hypoxia on the hormonal response to hypothalamic factors

Acute and chronic exposure to high altitude induces various physiological changes, including activation or inhibition of various hormonal systems. In response to activation processes, a desensitization of several pathways has been described, especially in the adrenergic system. In the present study, we aimed to assess whether the hypophyseal hormones are also subjected to a hypoxia-induced decrease in their response to hypothalamic factors. Basal levels of hormones and the responses of TSH, thyroid hormones, prolactin, sex hormones, and growth hormone to the injection of TRH, gonadotropin-releasing hormone, and growth hormone-releasing hormone (GHRH) were studied in eight men in normoxia and on prolonged exposure (3-4 days) to an altitude of 4,350 m. Thyroid hormones were elevated at altitude (+16 to +21%), while TSH levels were unchanged, and follicle-stimulating hormone and prolactin decreased, while leutinizing hormone was unchanged. Norepinephrine and cortisol levels were elevated, while no change was observed in levels of epinephrine, dopamine, growth hormone (GH), IGF-1, and IGFBP-3. The mean response to hypothalamic factors was similar in both altitudes for all studied hormones, although total T4 was lower in hypoxia during 45 to 60 min after injection. The effect of hypoxia on the hypophyseal response to hypothalamic factors was similar among subjects, except for the GH response to GHRH administration. We conclude that prolonged exposure to high-altitude hypoxia induces contrasted changes in hormonal levels, but the hypophyseal response to hypothalamic factors does not appear to be blunted.

Time course of endocrine changes in the hypophysis-gonad axis induced by hypobaric hypoxia in male rats

Chronic hypobaric hypoxia (CHH) induces a decrease in sperm output and spermatogenesis in male rats. The mechanisms that underlie these changes in testicular function are unknown and could involve changes in the hypophysis-gonad axis. We have tested the hypothesis that changes take place in the endocrine status (FSH, follicle stimulating hormone; LH, luteinizing hormone; testosterone) of rats subjected to CHH. Male Wistar rats were maintained under normobaric or hypobaric conditions (428 torr, 4,600 m). On days 0, 5, 15 and 30 post-exposure, 12 rats were anesthetized, their body weights were measured and blood samples were collected. The testicles were fixed in 4% formaldehyde and processed for histological analysis. In this time course, the FSH levels rose by day 5 post-exposure. On subsequent days, the FSH levels decreased in rats subjected to CHH with a tendency to remain higher than the normoxic group. The LH plasma levels decreased in rats exposed to CHH. Consistent with the decrease in LH levels, the plasma testosterone level decreased significantly after 30 days of CHH exposure. Integrated analysis of hormonal changes in rats subjected to CHH and the body dehydration that occurs in HH allows us to conclude that the effects of CHH on spermatogenesis may be partially related to changes in the hypophysis-gonad hormonal axis.

Simulation of long-haul flights in humans: prolonged mild hypoxia does not alter the circadian time structure of plasma testosterone and gonadotrophins

Mild hypobaric hypoxia caused by pressurisation may contribute to alter rhythmicity after long-haul flights, independently of the number of time zones crossed. In this controlled crossover study, we assessed the effects of two levels of hypoxia, equivalent to 8000 ft and 12,000 ft above sea level, on the rhythm of plasma concentrations of three hormones: testosterone, LH, and FSH. A hypoxia-induced decrease in LH and FSH has often been reported during mountaineering while testosterone is considered a marker of fatigue. Sixteen healthy male volunteers, aged 23-39 years, spent 8 h in a hypobaric chamber (08:00-16:30), simulating conditions at 8000 ft. This was followed by an additional 8 h four weeks later, simulating conditions at 12,000 ft. Plasma hormones were assayed every 2 h over two 24-h cycles (control and hypoxic-exposure cycles). We found no significant effects of hypoxia on the circadian profile of the gonadal axis hormones and, therefore, conclude that these hormones do not serve as valuable markers of post-flight alterations of the circadian system in human.

IRAD2 : Insuffisant respiratoire à domicile 2 (2e étude) effets d’une réhabilitation à domicile chez l’insuffisant respiratoire chronique dénutri

STATE OF THE ART

The IRAD2 trial is evaluating a 3-month home intervention which includes education, oral supplements, exercise and androgenic steroids in undernourished patients with chronic respiratory failure. The main objective is to increase the six-minute walking distance by more than 50 m with an improvement in health-related quality-of-life. Secondary end-points include a reduction in exacerbation rates by 25%, a reduction in health-related costs and an increase in survival during the year following intervention.

MATERIAL AND METHODS

This interventional, multi-centre, prospective, two-armed parallel, controlled trial is being conducted in 200 patients. In both groups, "Control" and "Rehabilitation", 7 home visits are scheduled during the 3-month intervention for education purpose. In the "Rehabilitation" group, patients will receive 160 mg/d of oral testosterone undecanoate in men, 80 mg/d in women, oral dietary supplements (563 kcal/d) and exercises on an ergometric bicycle 3 to 5 times a week.

EXPECTED RESULTS

In the event of significant responses to intervention, this trial would validate a comprehensive and global home-care for undernourished patients with chronic respiratory failure combining therapeutic education, oral supplements, androgenic substitution and physical activity.

Changes in Male Reproductive Function after High Altitude Mountaineering

The male reproductive functions of the members of the Masherbrum (7821 m) Expedition in 1999 were examined via semen analyses and endocrine tests. Specimens were collected from three subjects who had stayed above 5100 m for 21 to 24 days and above 6700 m for 4 to 5 days before departure and 1 month, 3 months, and 2 yr after returning from the expedition. Semen analyses showed no change in the semen volume. Sperm counts decreased after 1 month and had not recovered after 3 months, but they had recovered after 2 yr in all subjects. An increase in abnormally shaped sperm was also observed after 1 month, but had nearly recovered to the preexpedition state after 3 months. Endocrine tests revealed slightly decreased testosterone in the blood after 1 month, which had decreased still further after 3 months. The tests were completely normal after 2 yr. We suggest that a high altitude sojourn may induce reversible spermatogenic and Leydig cell dysfunction.

The effect of ski training at altitude and racing on pituitary, adrenal and testicular function in men

The effect of similar prolonged exercise on hormonal changes was studied at sea level and at moderate altitude. Four cross-country skiers participated in a 30-km race and five biathlonists in a 20-km race at sea level in Finland and during altitude training and racing at 1650 m in Les Saisies, France. Venous blood samples were taken at both altitudes before the race between 0800 and 0900 hours and 25-35 min after the race. Resting blood samples were also taken before and after the altitude training and the period of racing. Serum testosterone concentration was higher before the race at altitude than at sea level (19%, P < 0.02), and 30 min after the race growth hormone (GH) concentration was higher at sea level than at moderate altitude (P < 0.002). There were not significant differences in serum luteinising hormone between the altitudes. Serum cortisol concentration was higher after the altitude training and the period of racing than before (P < 0.02) but no difference was observed in testosterone. We concluded, that since the profiles of the anabolic-catabolic hormone concentrations measured are indicators of the performance level of athletes, our data indicated that to follow them during altitude training could be beneficial in optimizing training programme for individual athletes. We also concluded, that the lower GH concentration after racing at moderate altitude may have been a consequence of decreased racing speed and/or increased physical performance.

Effect of exposure to the altitude of 300 meters below sea-level on testosterone, luteinizing hormone, follicle-stimulating hormone and prolactin in man

Serum testosterone, luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin (PRL) responses to exposure to sea-level altitude (LA) were examined in 13 eugonadal males, age 21-22 yr, 3 and 5 days after residing at LA and on the second day of return to basal altitude 90 days later. After 3 days at their respective residence altitude, there was elevation in LH (p less than 0.05) and depression in testosterone levels (p less than 0.05), with similar results on day 5. These effects were all of transient nature, LH and testosterone concentrations returned to their basal levels on second day of the return to basal altitude. The FSH and PRL levels did not show any significant change during the stay at LA or after return to basal altitude. The observations suggest that exposure to LA is associated with increase in plasma levels of LH and decrease in testosterone. The decreased levels of testosterone could be due to a reduction in the sensitivity of the testis to LH, or due to inhibition of steroidogenesis in the testis.