W. R. de Vries

Growth hormone, insulin-like growthfactor I and cognitive function in adults

This review focuses on the possible contribution of the growth hormone (GH)-insulin-like growth factor I (IGF-I) axis to cognitive function. Binding sites for GH and IGF-I are found in various areas of the brain. Their distribution suggests that GH and IGF-I contribute to the function of the hippocampus, a brain structure important for the maintenance of cognitive functions such as learning and memory. Evidence for cognitive deficits in GH-deficient individuals has been found in various studies, some of which have shown that these deficits can be reversed by GH substitution therapy. In addition to examining conditions of GH deficiency, this article reviews studies evaluating the correlation between the cognitive deficits associated with ageing and age-related decreases in GH or IGF-I secretion. Based on the available data, one might hypothesize that relative GH or IGF-I deficiency could contribute to the deterioration of cognitive functions observed in the elderly.

Gastrointestinal symptoms in long-distance runners, cyclists, and triathletes: prevalence, medication, and etiology.

ObjectiveThe aim of this study was to determine the prevalence of exercise-related gastrointestinal (GI) symptoms and the use of medication for these symptoms among long-distance runners, cyclists, and triathletes, and to determine the relationship of different variables to GI symptoms.MethodsA mail questionnaire covering the preceding 12 months was sent to 606 well-trained endurance type athletes: 199 runners (114 men and 85 women), 197 cyclists (98 men and 99 women), and 210 triathletes (110 men and 100 women) and sent back by 93%, 88%, and 71% of these groups, respectively. Symptoms were evaluated with respect to the upper (nausea, vomiting, belching, heartburn, chest pain) or lower part of the GI tract (bloating, GI cramps, side ache, urge to defecate, defecation, diarrhea). For statistical analysis, Mann-Whitney U test, Fisher exact test, or Student t test were used.ResultsRunners experienced more lower (prevalence 71%) than upper (36%) GI symptoms during exercise. Cyclists experienced both upper (67%) and lower (64%) symptoms. Triathletes experienced during cycling both upper (52%) and lower (45%) symptoms, and during running more lower (79%) than upper (54%) symptoms. Bloating, diarrhea, and flatulence occurred more at rest than during exercise among all subjects. In general, exercise-related GI symptoms were significantly related to the occurrence of GI symptoms during nonexercise periods, age, gender, diet, and years of training. The prevalence of medication for exercise-related GI symptoms was 5%, 6%, and 3% for runners, cyclists, and triathletes, respectively.ConclusionsLong-distance running is mainly associated with lower GI symptoms, whereas cycling is associated with both upper and lower symptoms. Triathletes confirm this pattern during cycling and running. The prevalence of medication for exercise-related GI symptoms is lower in the Netherlands in comparison with other countries, in which a prevalence of 10–18% was reported. More research on the possible predisposition of athletes for GI symptoms during exercise is needed.

Detection and treatment of claudication due to functional iliac obstruction in top endurance athletes: a prospective study

BACKGROUND Endurance athletes often have restrictions in flow in their iliac arteries during exercise. Such restrictions have previously been ascribed solely to intravascular lesions. We postulate that flow could also be restricted by functional kinking in the arteries, and that surgical release of these kinks might be an effective treatment. METHODS We prospectively studied 80 endurance athletes who had complaints suggestive of flow restriction in the iliac arteries of one (n=74) or both (6) legs (total 92 legs). Using vascular diagnostic tools, we examined athletes while they were doing activities that often provoke flow restrictions. Restrictions were determined by measurement of systolic pressure in the ankle after exercise; peak systolic velocities were measured with echo-doppler. Kinks were detected with echo-doppler and magnetic-resonance angiography. When functional kinking was diagnosed as the cause of the restriction, the athlete was offered surgery to release the iliac arteries, as part of our prospective study. FINDINGS We recorded flow restrictions in the iliac arteries of 58 of 92 (63%) legs. In 40 of these legs (69%), kinks were the most important cause of the restriction, making these legs suitable for surgical release. We operated on 23 of 58 (40%) legs. All athletes who had an operation subjectively improved. Maximum workload in a cycling test and ankle pressure significantly improved after the operation. 20 (87%) athletes were able to successfully return to their desired high level of competition. INTERPRETATION Our sports-specific protocol is effective in detecting kinking of the iliac arteries as a cause for flow restriction in athletes who have few intravascular abnormalities when investigated with conventional vascular diagnostic tools. Surgical treatment directed at the kinking was less invasive and therefore a better alternative to vascular reconstruction in these athletes.

Age-sensitive cognitive function, growth hormone and insulin-like growth factor 1 plasma levels in healthy older men.

Circulating levels of growth hormone (GH) change during the process of aging. Decline of cognitive functioning with aging is also well established. In this study, we investigated whether insulin-like growth factor 1 (IGF-1) and the GH response to a challenge of GH-releasing hormone and GH-releasing peptide 6 were associated with age-sensitive cognitive functions, but not with functions that do not decline with aging, in 17 healthy male subjects aged between 66 and 76 years. In addition, relations with anthropometric measures were examined. Neuropsychological performance was scored on tests of variables not sensitive to aging (general knowledge, vocabulary, basic visual perception and reading ability), and of variables sensitive to aging (visuoconstructive ability, perceptual motor and mental processing speed, and verbal long-term memory). After correcting for education, the serum GH response was significantly associated with two age-sensitive cognitive tests (measures of mental processing speed), but with none of the tests not sensitive to aging. However, the direction of the association was opposite to the relation between IGF-1 and these cognitive tests: higher levels of GH response were associated with poorer cognitive performance, whereas higher levels of IGF-1 were associated with better performance. GH response, but not IGF-1, was inversely correlated with body mass index. The results are in accordance with previous research suggesting a disruption of the relation between IGF-1 and GH secretion in older age.

The sloping alveolar plateau at synchronous ventilation

We performed model calculations on the slope of the alveolar plateau at single breath washout of helium (He) and sulphurhexafluoride (SF6). Calculations were carried out on an extensible axissymmetric lung model, which was synchronously ventilated either equally or unequally. The calculated slopes of the alveolar plateau were small (<0.3%), which is in agreement with the results of other investigators. However, calculations carried out on a synchronously equally ventilated axis-asymmetric lung model related to the terminal lung unit (acinus), yielded slopes for the alveolar plateau ranging from 0 up to 14% per liter between 1.2 and 1.8 l expired volume. Even with a post inspiratory apnea of 1 s, we still found slopes ranging from 0–4%.Our findings are in contrast to the conclusions of Engel et al. (1979), who ascribe the slope of the alveolar plateau to asynchronous unequal ventilation.

Uptake of highly soluble gases in the epithelium of the conducting airways

Short duration washin and washout experiments were carried out with the gases ether (diethyl ether), ethyl acetate and acetone in order to study the excretion behaviour in the lung of gases highly soluble in blood and tissues. Carbon dioxide (CO2) was analyzed as a reference gas during the washout. The excretion values for acetone were generally the lowest, those for ether the highest, and intermediate ones were obtained for ethyl acetate. These results are in accord with the experimental data of others. Analysis of the washout curves shows that for acetone the volume of gas expired before the beginning of phase II is considerably smaller than found for CO2 and ether. During washout, the slope of the alveolar plateau for acetone is negative for the first few breaths and becomes positive thereafter; however, it remains lower than the slopes for CO2 and ether, which are always positive. These two phenomena occurring during washout clearly demonstrate that the acetone in the expired air must originate from the epithelial tissue lining the conducting airways. We conclude, therefore, that, in terms of gas transport, the conducting airways behave differently for poorly and highly soluble gases and this provides a physiological basis for the deviating excretion behaviour of highly soluble gases.

Somatotropic-axis deficiency affects brain substrates of selective attention in childhood-onset growth hormone deficient patients.

Reduced levels of growth hormone (GH) and insulin-like growth factor-1 (IGF-1) are associated with deteriorated cognitive performance in senescence. Little work has been done on the effect of GH and IGF-1 on a crucial aspect of cognition, selective attention. This study investigated the effect of GH/IGF-1 on performance and brain potentials (EEG) during a selective-attention task in patients with low levels of GH and IGF-1 (childhood-onset growth hormone deficiency) compared to healthy controls. Detection of occasional visual target patterns was impaired in patients. This was paralleled by a reduction in an attention-related brain potential, which has been associated previously with anterior cingulate cortex functioning.

Seasonal changes in performance and free testosterone: cortisol ratio of elite female rowers

SummaryThe aim of this study was to investigate the seasonal behaviour of the plasma free testosterone: cortisol ratio (FTCR) and to relate hormonal changes to daily training volume and performance parameters on a rowing ergometer in elite female rowers. During 9 months of training preceding the 1988 Olympic Games the resting values of the FTCR in six elite female rowers were regularly (ten times) studied. Daily training volume was analysed in terms of rowed distance (lrowad) and time (t). In addition, two performance parameters, the power at 4.0 mmol·l−1 lactate concentration in the blood and the maximal power, were determined by a test on a rowing ergometer. The results indicated that the mean FTCR test value did not differ significantly from the level of the initial test or from the mean value of the directly preceding test. A significant negative correlation (r=−0.98, P<0.01) between FTCR and lrowed was found in a period i.e. at a training camp, when there was a sudden increase in training volume. When FTCR was related to t a significant positive correlation (r=0.88, P<0.05) was found only for the period at the training camp. Our data further suggested that the FTCR alone was not an adequate indicator for the anabolic/catabolic balance in elite female rowers. This finding was contrary to previous findings in elite male rowers. However, in training practice the FTCR seems useful as an indicator of the hormonal training status of elite female rowers when complemented with data about total and free testosterone, performance parameters and knowledge concerning cyclic variations of the FTCR.

The effect of omeprazole on gastro-oesophageal reflux and symptoms during strenuous exercise

: Strenuous exercise exacerbates gastro‐oesophageal reflux and symptoms and this may be diminished by antisecretory medication with omeprazole.

Can we detect non-functional overreaching in young elite soccer players and middle-long distance runners using field performance tests?

Objective To study whether field performance tests can make a valid distinction between non-functionally overreaching (NFO) athletes and control athletes. Design Monthly field performance tests were used to determine a performance decrement (PD) throughout a season. Athletes with a minimum of 1 month PD were compared with control athletes without a PD on mood characteristics and resting levels of stress hormones. Setting Sporting field and sports medical laboratory. Participants 129 young elite athletes, 77 soccer players and 52 middle-long distance runners were followed prospectively during the 2006–2007 season. Fifteen of them were invited to the laboratory. Eight athletes showed a performance decrease lasting longer than 1 month, and seven athletes without a performance decrease acted as their controls. Main outcome measures Performance changes over time were measured using field tests. Profile of Mood States and resting levels of adrenocorticotrophic hormone (ACTH) and cortisol in blood were measured in the laboratory. Results PD athletes showed several symptoms typical of the non-functional state of overreaching (OR). The PD group scored higher on depression and anger than controls. They also showed a specific pattern of correlations between negative mood subscales (tension, fatigue and depression), which was absent in controls. ACTH levels at rest were similar, but lower cortisol levels in PD athletes pointed at a blunted cortisol response. Cortisol levels were decoupled from ACTH levels only in PD athletes. Conclusions Implementing performance-related criteria in field tests can help coaches and sports physicians to distinguish NFO athletes from athletes with balanced workload and recovery.