Physical exercise-induced changes and season-associated differences in the pituitary-ovarian function of runners and joggers.

The hormonal responses to energetic chronic exercise and to seasonal shift from autumn to spring were evaluated by measuring concentrations of serum FSH, LH, PRL, estradiol (E2), progesterone (P), testosterone (T), and sex hormone-binding globuline (SHBG) during 1 menstrual cycle in the autumn (light training season) and 1 in the spring (hard training season) in 18 endurance runners and 12 age-matched nonrunning women, and in 13 joggers and 11 age-matched nonjogging women. The appearance, growth, and maximal size of the ovarian follicles were monitored by ultrasonography. The high intensity training of the runners was associated with decreased concentrations of FSH on cycle days 7-8 in the autumn, E2 on cycle days 12-13 in the spring and days 22-23 in both seasons, P on cycle days 20-21 in both seasons and days 22-23 in the autumn, and T on cycle days 12-13, 14-15, and 22-23 in the spring. Jogging, however, did not alter the concentrations of these hormones. Using as criteria the presence of 2 or 3 abnormal values of the 3 indicators used for evaluation of folliculogenesis (midfollicular E2 lower than 0.09 nmol/liter, luteal phase P lower than 7 nmol/liter, and peak diameter of the largest ovarian follicle less than 15 mm), seriously disturbed folliculogenesis was found in 50% of the 32 study cycles of the runners and 9% of the 23 cycles of their controls (P less than 0.01). In all four study groups, there was a significant seasonal difference in the concentrations of ovarian hormones, with lowered E2, P, and T levels in the autumn. There were no differences in the serum concentrations of SHBG between the study groups or between the autumn and the spring. High training activity and a dark photoperiod appeared to independently suppress ovarian activity and were not associated with chronic changes in anterior pituitary hormone or SHBG concentrations.

Depressed follicle-stimulating hormone, luteinizing hormone, and prolactin responses to the luteinizing hormone-releasing hormone, thyrotropin-releasing hormone, and metoclopramide test in endurance runners in the hard-training season.

The responses of serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) to luteinizing hormone-releasing hormone (LH-RH) and the responses of prolactin (PRL) to thyrotropin-releasing hormone (TRH) and metoclopramide (MC) were measured in the late luteal phase of the cycle in 12 endurance runners and 11 control women and in 12 joggers and 7 control women. LH-RH (100 micrograms) and TRH (200 micrograms) were injected intravenously at the beginning of the test, and MC (10 mg) was injected 60 minutes later. Blood samples were obtained before and 20, 60, 80, and 120 minutes after the beginning of the test. Runners had significantly lower serum concentrations of estradiol and progesterone than control subjects, whereas the concentrations of FSH, LH, and PRL were similar at the beginning of the study. Compared with their controls, the runners had significantly lower FSH (P less than 0.05) and LH responses at 20 minutes (P less than 0.05) and lower LH responses at 80 minutes (P less than 0.01) to LH-RH and lower PRL responses to MC 20 minutes after MC injection (P less than 0.05). Joggers and their control subjects had similar LH, FSH, and PRL responses to these pharmacologic stimuli. It is concluded that decreased ovarian activity explains, at least partly, the lowered responses of FSH and LH to LH-RH and the lowered response of PRL to MC in endurance runners.

Adrenocortical function of female endurance runners and joggers.

The aim of the present study was to investigate the long-term effects of endurance exercise on the function of the adrenal cortex of 18 female runners, 12 control subjects, and 13 joggers and their 11 control subjects by measuring the serum concentrations of cortisol and dehydroepiandrosterone sulfate and the responses of cortisol to intravenous ACTH injection. All of the participants were studied over one menstrual cycle, during a light training period in the autumn and a hard training period in the spring. There were no significant between-group differences in the concentrations of cortisol in the autumn or the spring. However, the mean spring vs autumn concentrations of cortisol were significantly increased in runners during the follicular and luteal phases of the menstrual cycle. The concentrations of cortisol in the ACTH response test were also increased at 30 and 60 min in runners and all the time in joggers in spring, in relation to the respective values in the autumn. The absolute and relative rises of cortisol in response to ACTH did not differ between the groups, but the relative spring vs autumn increase of cortisol was significantly higher at 60 min in the runners and lower at 30 min in the control subjects of the joggers. There were no differences in the serum concentrations of dehydroepiandrosterone sulfate between the groups, or between spring and autumn values in any group. In conclusion, chronic endurance exercise per se did not appear to alter the function of the adrenal cortex, while an undefined spring-associated factor, possibly the high luminosity, appeared to induce an increase in cortisol secretion in female runners.

Behaviour of cyclic bank voles under risk of mustelid predation: do females avoid copulations?

Mustelid odours have been shown to suppress breeding in captive bank voles (Clethrionomys glareolus) from cyclic populations (Ylönen 1989; Ylönen and Ronkainen 1994). The mechanism behind the suppression is unknown. Based on a series of behavioural trials and breeding experiments with pairs of bank voles in breeding condition, we suggest that the primary cause for breeding suppression is a change in female mating behaviour. Experimental female-male pairs (n=34) exposed to mustelid odour decreased their general activity compared to control pairs (n=34). When encountering males in behavioural trials, females exposed to stoat odour were more aggressive and actively avoided precopulatory behaviours of males. No copulations were observed in experimental pairs compared to five in control pairs during the behavioural trials. Males actively approached females in general but male behaviour did not change under exposure to mustelid odours. We suggest that females are more vulnerable to mustelid predators than males and therefore actively avoid copulations in the (indirect) presence of mustelids. As well as this behavioural response, internal abortive mechanisms (cf. Bruce 1959) could play a role in the observed breeding suppression.

Pubertal and menstrual disorders of female runners, skiers and volleyball players.

In order to evaluate the onset of puberty and the presence of menstrual disorders in Finnish sportswomen with different training programs, 53 long-distance runners, 39 skiers and their 93 controls, and 63 volleyball players with 64 controls were interviewed. All the sportswomen had trained intensively for several years and were in the top category of their sport in Finland. Menarche and thelarche in all the sportswomen and also pubarche in the volleyball players developed significantly later than in their controls. The runners and skiers (43%) suffered significantly more often from menstrual irregularities than their controls (27%), whereas volleyball players (19%) did not differ from their controls (13%) in this respect. Among runners and skiers, but not among volleyball players, premenarchal start of sports activity had an aggravating effect on these endocrine disorders. Dysmenorrhea was found to occur more seldom in sportswomen than in the control subjects, and physical exercise often alleviated menstrual distress. Because the runners and skiers trained as often and used as much time for their sport as the volleyball players, the more common occurrence of their menstrual disorders may be due to the nature of training and competition activity which is characterized by endurance physical exercise.

Effects of physical exercise on the serum concentration of melatonin in female runners.

The serum melatonin concentration was measured in 11 runners before and after a long-distance race, and during one menstrual cycle of another 11 runners who were performing a strenuous training programme, and in their 12 control subjects. The concentration of melatonin was significantly increased (p less than 0.05) after the competition, whereas during one menstrual cycle of female runners it did not differ from the corresponding concentrations of non-athletes. Training did not cause any chronic changes in melatonin secretion, and the serum melatonin increases following the physical exercise remained clearly below the nocturnal level. Hence, the antigonadotropic effect of endurance running activity is very likely not a melatonin-associated phenomenon.