Bone turnover in amenorrhoeic and eumenorrhoeic women distance runners

Medical and physiological complications of exercise for individuals with an eating disorder: A narrative review

Individuals with eating disorders (ED) experience prolonged malnutrition, binge episodes, and compensatory behaviours that affect every organ system. Psychological and physiological symptoms are worsened with comorbid dysfunctional exercise, seen in up to 80% of those with an ED. Although return to exercise is an important component of treatment and recovery, little is known about the contraindications and risks of exercise engagement specific to those with an ED. This paper provides a comprehensive narrative review of the medical and physiological complications of engaging in exercise during ED treatment and outlines when exercise may be contraindicated or used in modified or cautionary ways. We conducted a literature search on MEDLINE, PubMed, and PsychArticles to identify relevant articles, which yielded six categories of medical and physiological complications of ED that may be exacerbated by exercise: energy availability, cardiovascular health, electrolyte abnormalities, biomedical function markers, sex hormones, and body composition. We summarize the evidence for these complications for readers and offer an initial set of recommendations for incorporating exercise during ED treatment based on our findings. This review may serve as a resource for members of ED treatment teams to help evaluate more readily and confidently whether exercise is safe for individual patients and when modifications and caution may be warranted.

Menstrual dysfunction and body weight dissatisfaction among Finnish young athletes and non-athletes

To determine the prevalence of menstrual dysfunction (MD; ie, oligomenorrhea or amenorrhea) and attitudes toward body weight among athletes and non-athletes, we studied a cohort of athletes and non-athletes, in adolescence (14-16 years) and subsequently in young adulthood (18-20 years). We further studied the differences between athletes reporting MD and eumenorrheic athletes at both time periods and identified physical and behavioral characteristics that might predict MD in young adulthood. Data were collected using questionnaires, accelerometers, and a pre-participation screening. In adolescence, the athletes reported current primary amenorrhea more often than the non-athletes (4.7% vs 0%, P = .03). In young adulthood, athletes reported MD more frequently than non-athletes (38.7% vs 5.6%, P < .001). Athletes had less desire than non-athletes to lose weight at both time points, and in adolescence, athletes were more satisfied with their weight. However, about one fifth of the athletes and about 40% of the non-athletes experienced body weight dissatisfaction at both time points. In adolescence, athletes reporting MD had lower BMI than eumenorrheic athletes. In young adulthood, athletes with MD were more physically active than eumenorrheic athletes. The only longitudinal predictor of MD in young adulthood was MD in adolescence. Our findings indicate that MD is relatively frequent among young Finnish athletes. However, athletes appear to have a smaller tendency to experience body weight dissatisfaction than their non-athletic peers. MD seems to track from adolescence to adulthood, suggesting that there is a need to focus on possible causes at the earliest feasible phase of an athlete's career.

The Unexplored Crossroads of the Female Athlete Triad and Iron Deficiency: A Narrative Review

Despite the severity and prevalence of iron deficiency in exercising women, few published reports have explored how iron deficiency interacts with another prevalent and severe condition in exercising women: the 'female athlete triad.' This review aims to describe how iron deficiency may interact with each component of the female athlete triad, that is, energy status, reproductive function, and bone health. The effects of iron deficiency on energy status are discussed in regards to thyroid function, metabolic fuel availability, eating behaviors, and energy expenditure. The interactions between iron deficiency and reproductive function are explored by discussing the potentially impaired fertility and hyperprolactinemia due to iron deficiency and the alterations in iron metabolism due to menstrual blood loss and estrogen exposure. The interaction of iron deficiency with bone health may occur via dysregulation of the growth hormone/insulin-like growth factor-1 axis, hypoxia, and hypothyroidism. Based on these discussions, several future directions for research are presented.

Endocrine Effects of Relative Energy Deficiency in Sport

The term Relative Energy Deficiency in Sport was introduced by the International Olympic Committee in 2014. It refers to the potential health and performance consequences of inadequate energy for sport, emphasizing that there are consequences of low energy availability (EA; typically defined as <30 kcal·kg^-1 fat-free mass·day^-1) beyond the important and well-established female athlete triad, and that low EA affects populations other than women. As the prevalence and consequences of Relative Energy Deficiency in Sport become more apparent, it is important to understand the current knowledge of the hormonal changes that occur with decreased EA. This paper highlights endocrine changes that have been observed in female and male athletes with low EA. Where studies are not available in athletes, results of studies in low EA states, such as anorexia nervosa, are included. Dietary intake/appetite-regulating hormones, insulin and other glucose-regulating hormones, growth hormone and insulin-like growth factor 1, thyroid hormones, cortisol, and gonadal hormones are all discussed. The effects of low EA on body composition, metabolic rate, and bone in female and male athletes are presented, and we identify future directions to address knowledge gaps specific to athletes.

Endocrine disorders in adolescent and young female athletes: impact on growth, menstrual cycles, and bone mass acquisition

CONTEXT

Puberty is a crucial period of dramatic hormonal changes, accelerated growth, attainment of reproductive capacity, and acquisition of peak bone mass. Participation in recreational physical activity is widely acknowledged to provide significant health benefits in this period. Conversely, intense training imposes several constraints, such as training stress and maintenance of very low body fat to maximize performance. Adolescent female athletes are therefore at risk of overtraining and/or poor dietary intake, which may have several consequences for endocrine function. The "adaptive" changes in the hypothalamic-pituitary-gonadal, -adrenal, and somatotropic axes and the secretory role of the adipose tissue are reviewed, as are their effects on growth, menstrual cycles, and bone mass acquisition.

DESIGN

A systematic search on Medline between 1990 and 2013 was conducted using the following terms: "intense training," "physical activity," or "exercise" combined with "hormone," "endocrine," and "girls," "women," or "elite female athletes." All articles reporting on the endocrine changes related to intense training and their potential implications for growth, menstrual cycles, and bone mass acquisition were considered.

RESULTS AND CONCLUSION

Young female athletes present a high prevalence of menstrual disorders, including delayed menarche, oligomenorrhea, and amenorrhea, characterized by a high degree of variability according to the type of sport. Exercise-related reproductive dysfunction may have consequences for growth velocity and peak bone mass acquisition. Recent findings highlight the endocrine role of adipose tissue and energy balance in the regulation of homeostasis and reproductive function. A better understanding of the mechanisms whereby intense training affects the endocrine system may orient research to develop innovative strategies (ie, based on nutritional or pharmacological approaches and individualized modalities of training and competition) to improve the medical care of these adolescents and protect their reproductive function.

Dietary intervention restored menses in female athletes with exercise-associated menstrual dysfunction with limited impact on bone and muscle health

Exercise-related menstrual dysfunction (ExMD) is associated with low energy availability (EA), decreased bone mineral density (BMD), and increased risk of musculoskeletal injury. We investigated whether a 6-month carbohydrate-protein (CHO-PRO) supplement (360 kcal/day, 54 g CHO/day, 20 g PRO/day) intervention would improve energy status and musculoskeletal health and restore menses in female athletes (n = 8) with ExMD. At pre/post-intervention, reproductive and thyroid hormones, bone health (BMD, bone mineral content, bone markers), muscle strength/power and protein metabolism markers, profile of mood state (POMS), and energy intake (EI)/energy expenditure (7 day food/activity records) were measured. Eumenorrheic athlete controls with normal menses (Eumen); n = 10) were measured at baseline. Multiple linear regressions were used to evaluate differences between groups and pre/post-intervention blocking on participants. Improvements in EI (+382 kcal/day; p = 0.12), EA (+417 kcal/day; p = 0.17) and energy balance (EB; +466 kcal/day; p = 0.14) were observed with the intervention but were not statistically significant. ExMD resumed menses (2.6 ± 2.2-months to first menses; 3.5 ± 1.9 cycles); one remaining anovulatory with menses. Female athletes with ExMD for >8 months took longer to resume menses/ovulation and had lower BMD (low spine (ExMD = 3; Eumen = 1); low hip (ExMD = 2)) than those with ExMD for <8 months; for 2 ExMD the intervention improved spinal BMD. POMS fatigue scores were 15% lower in ExMD vs. Eumen (p = 0.17); POMS depression scores improved by 8% in ExMD (p = 0.12). EI, EA, and EB were similar between groups, but the intervention (+360 kcal/day) improved energy status enough to reverse ExMD despite no statistically significant changes in EI. Similar baseline EA and EB between groups suggests that some ExMD athletes are more sensitive to EA and EB fluctuations.

Body composition and reproductive function exert unique influences on indices of bone health in exercising women

Reproductive function, metabolic hormones, and lean mass have been observed to influence bone metabolism and bone mass. It is unclear, however, if reproductive, metabolic and body composition factors play unique roles in the clinical measures of areal bone mineral density (aBMD) and bone geometry in exercising women. This study compares lumbar spine bone mineral apparent density (BMAD) and estimates of femoral neck cross-sectional moment of inertia (CSMI) and cross-sectional area (CSA) between exercising ovulatory (Ov) and amenorrheic (Amen) women. It also explores the respective roles of reproductive function, metabolic status, and body composition on aBMD, lumbar spine BMAD and femoral neck CSMI and CSA, which are surrogate measures of bone strength. Among exercising women aged 18-30 years, body composition, aBMD, and estimates of femoral neck CSMI and CSA were assessed by dual-energy x-ray absorptiometry. Lumbar spine BMAD was calculated from bone mineral content and area. Estrone-1-glucuronide (E1G) and pregnanediol glucuronide were measured in daily urine samples collected for one cycle or monitoring period. Fasting blood samples were collected for measurement of leptin and total triiodothyronine. Ov (n = 37) and Amen (n = 45) women aged 22.3 ± 0.5 years did not differ in body mass, body mass index, and lean mass; however, Ov women had significantly higher percent body fat than Amen women. Lumbar spine aBMD and BMAD were significantly lower in Amen women compared to Ov women (p < 0.001); however, femoral neck CSA and CSMI were not different between groups. E1G cycle mean and age of menarche were the strongest predictors of lumbar spine aBMD and BMAD, together explaining 25.5% and 22.7% of the variance, respectively. Lean mass was the strongest predictor of total hip and femoral neck aBMD as well as femoral neck CSMI and CSA, explaining 8.5-34.8% of the variance. Upon consideration of several potential osteogenic stimuli, reproductive function appears to play a key role in bone mass at a site composed of primarily trabecular bone. However, lean mass is one of the most influential predictors of bone mass and bone geometry at weight-bearing sites, such as the hip.

Obstacles in the optimization of bone health outcomes in the female athlete triad

Maintaining low body weight for the sake of performance and aesthetic purposes is a common feature among young girls and women who exercise on a regular basis, including elite, college and high-school athletes, members of fitness centres, and recreational exercisers. High energy expenditure without adequate compensation in energy intake leads to an energy deficiency, which may ultimately affect reproductive function and bone health. The combination of low energy availability, menstrual disturbances and low bone mineral density is referred to as the 'female athlete triad'. Not all athletes seek medical assistance in response to the absence of menstruation for 3 or more months as some believe that long-term amenorrhoea is not harmful. Indeed, many women may not seek medical attention until they sustain a stress fracture. This review investigates current issues, controversies and strategies in the clinical management of bone health concerns related to the female athlete triad. Current recommendations focus on either increasing energy intake or decreasing energy expenditure, as this approach remains the most efficient strategy to prevent further bone health complications. However, convincing the athlete to increase energy availability can be extremely challenging. Oral contraceptive therapy seems to be a common strategy chosen by many physicians to address bone health issues in young women with amenorrhoea, although there is little evidence that this strategy improves bone mineral density in this population. Assessment of bone health itself is difficult due to the limitations of dual-energy X-ray absorptiometry (DXA) to estimate bone strength. Understanding how bone strength is affected by low energy availability, weight gain and resumption of menses requires further investigations using 3-dimensional bone imaging techniques in order to improve the clinical management of the female athlete triad.

Different effects on bone strength and cell differentiation in pre pubertal caloric restriction versus hypothalamic suppression

Hypothalamic amenorrhea and energy restriction during puberty affect peak bone mass accrual. One hypothesis suggests energy restriction alters hypothalamic function resulting in suppressed estradiol levels leading to bone loss. However, both positive and negative results have been reported regarding energy restriction and bone strength. Therefore, the purpose of this study was to investigate energy restriction and hypothalamic suppression during pubertal onset on bone mechanical strength and the osteogenic capacity of bone marrow-derived cells in two models: female rats treated with gonadotropin releasing hormone antagonists (GnRH-a) or 30% energy restriction. At 23 days of age, female Sprague Dawley rats were assigned to three groups: control group (C, n=10), GnRH-a group (n=10), and Energy Restriction (ER, n=12) group. GnRH-a animals received daily injections for 27 days. The animals in the ER group received 70% of the control animals' intake. After sacrifice (50 days of age), body weight, uterine and muscle weights were measured. Bone marrow-derived stromal cells were cultured and assayed for proliferation and differentiation into osteoblasts. Outcome measures included bone strength, bone histomorphometry and architecture, serum IGF-1 and osteocalcin. GnRH-a suppressed uterine weight, decreased osteoblast proliferation, bone strength, trabecular bone volume and architecture compared to control. Elevated serum IGF-1 and osteocalcin levels and body weight were found. The ER model had an increase in osteoblast proliferation compared to the GnRH-a group, similar bone strength relative to body weight and increased trabecular bone volume in the lumbar spine compared to control. The ER animals were smaller but had developed bone strength sufficient for their size. In contrast, suppressed estradiol via hypothalamic suppression resulted in bone strength deficits and trabecular bone volume loss. In summary, our results support the hypothesis that during periods of nutritional stress the increased vertebral bone volume may be an adaptive mechanism to store mineral which differs from suppressed estradiol resulting from hypothalamic suppression.

Effects of physical activity on bone remodeling

Physical exercise is recommended to improve bone mass in growing children and decrease bone loss in elderly men and women. However, the specific mechanisms by which exercise influences bone metabolism are still not thoroughly understood. The effect of physical activity on the skeleton is generally evaluated by dual-energy x-ray absorptiometry, which measures bone mineral density. However, a relatively long period is needed to detect even a minor variation in bone mineral density with this technique, limiting its usefulness. Bone biochemical markers that reflect the cellular activities of bone formation and resorption are thus also useful tools, both to monitor the acute effects of exercise on bone remodeling and to investigate the mechanisms of exercise-induced changes in bone mass. This article describes the effects of physical activity on bone remodeling in various types of population. The comparison of sedentary individuals and athletes with many years of high-volume sports practice, for example, has clarified some of the long-term effects of exercise. Moreover, the acute variation in bone cell activities after brief exercise or a training program is here examined. The interpretation of results is difficult, however, because of the many parameters, such as age, that are involved. The various populations are therefore categorized to reflect the biological factors implicated in the modulation of bone marker response during exercise.

Physiologic and behavioral indicators of energy deficiency in female adolescent runners with elevated bone turnover

BACKGROUND

Female adolescent runners have an elevated prevalence of low bone mass for agemdashan outcome that may be partially due to inadequate energy intake.

OBJECTIVE

The objective was to evaluate diet, menstrual history, serum hormone concentrations, and bone mass in female adolescent runners with normal or abnormal bone turnover.

DESIGN

Thirty-nine cross-country runners (age: 15.7 plusmn 0.2 y) participated in the study, which included a 7-d dietary assessment with the use of a food record and daily 24-h dietary recalls; serum measures of insulin-like growth factor I, estradiol, leptin, parathyroid hormone, progesterone, triiodothyronine, 25-hydroxycholecalciferol, bone-specific alkaline phosphatase (BAP), and cross-linked C-telopeptides of type I collagen (CTX); an evaluation of height, weight, bone mass, and body composition with the use of dual-energy X-ray absorptiometry; and a questionnaire to assess menses and sports participation. Age- and sex-specific BAP and CTX concentrations of at least the 97th percentile and no greater than the third percentile, respectively, were considered abnormal.

RESULTS

All abnormal BAP and CTX concentrations fell within the elevated ( ge 97%) range. Runners with an elevated bone turnover (EBT) (n = 13) had a lower body mass, fewer menstrual cycles in the past year, lower estradiol and 25-hydroxycholecalciferol concentrations, and a higher prevalence of body mass index lt 10% for age, vitamin D insufficiency, amenorrhea, and low bone mass. Girls with EBT consumed less than the recommended amounts of energy and had a higher prevalence of consuming lt 1300 mg Ca than did those with normal bone turnover.

CONCLUSIONS

Runners with EBT had a profile consistent with energy deficiency. Nutritional support to increase energy, calcium intake, and 25-hydroxycholecalciferol concentrations may improve bone mineral accrual in young runners with EBT. This trial was registered at clinicaltrials.gov as NCT01059968.

Anorexia, bulimia, and the female athlete triad: evaluation and management

The female athlete triad is an increasingly prevalent condition involving disordered eating, amenorrhea, and osteoporosis. An athlete can suffer from all 3 components of the triad, or just 1 or 2 of the individual conditions. The main element underlying all the aspects of the triad is an adaptation to a negative caloric balance. Screening for these disorders should be an important component of an athlete's care. Prevention and treatment should involve a team approach, including a physician, a nutritionist, and a mental health provider.

The presence of both an energy deficiency and estrogen deficiency exacerbate alterations of bone metabolism in exercising women

BACKGROUND

Bone loss in amenorrheic athletes has been attributed to energy deficiency-related suppression of bone formation, but not increased resorption despite hypoestrogenism.

OBJECTIVE

To assess the independent and combined effects of energy deficiency and estrogen deficiency on bone turnover markers in exercising women.

DESIGN

PINP, osteocalcin, U-CTX-I, TT3, leptin, and ghrelin were measured repeatedly, and bone mineral density (BMD) was measured once in 44 exercising women. Resting energy expenditure (REE) was used to determine energy status (deficient or replete) and was corroborated with measures of metabolic hormones. Daily levels of urinary estrone and pregnanediol glucuronides (E1G, PdG), were assessed to determine menstrual and estrogen status. Volunteers were then retrospectively categorized into 4 groups: 1) Energy Replete+Estrogen Replete (EnR+E2R), (n=22), 2) Energy Replete+Estrogen Deficient (EnR+E2D), (n=7), 3) Energy Deficient+Estrogen Replete (EnD+E2R), (n=7), and 4) Energy Deficient+Estrogen Deficient (EnD+E2D), (n=8).

RESULTS

The groups were similar (p>0.05) with respect to age (24.05+/-1.75 yrs), weight (57.7+/-2.2 kg), and BMI (21.05+/-0.7 kg/m2). By design, REE/FFM (p=0.028) and REE:pREE (p<0.001) were lower in the EnD vs. EnR group, and the E2D group had a lower REE:pREE (p=0.005) compared to the E2R group. The EnD+E2D group had suppressed PINP (p=0.034), and elevated U-CTX-I (p=0.052) and ghrelin (p=0.028) levels compared to the other groups. These same women also had convincing evidence of energy conservation, including TT3 levels that were 29% lower (p=0.057) and ghrelin levels that were 44% higher (p=0.028) than that observed in the other groups. Energy deficiency was associated with suppressed osteocalcin, and TT3 (p<0.05), whereas estrogen deficiency was associated with decreased E1G (p<0.02), and lower L2-L4 BMD (p=0.033). Leptin was significant in predicting markers of bone formation, but not markers of bone resorption.

CONCLUSIONS

When the energy status of exercising women was adequate (replete), there were no apparent perturbations of bone formation or resorption, regardless of estrogen status. Estrogen deficiency in exercising women, in the presence of an energy deficiency, was associated with bone loss and involved suppressed bone formation and increased bone resorption. These findings underscore the importance of avoiding energy deficiency, which is associated with hypoestrogenism, to avoid bone health problems.

Anorexia, bulimia, and the athletic triad: evaluation and management

Caloric restriction caused by undernutrition or over-exercise is increasingly common and has significant health consequences such as hypothalamic amenorrhea, infertility, attainment of low peak bone mass, and bone loss leading to fracture. In these patients, the pathophysiology of amenorrhea and bone loss is multifactorial, involving hormones that integrate the nutritional state with the hypothalamic-pituitary-ovarian axis, including leptin and possibly ghrelin. The pathophysiology of bone loss includes nutritional deficiencies, possibly estrogen deficiency, and direct and indirect effects of leptin on bone. Identifying patients at risk for low bone mineral density and fracture is important, as is screening with dual energy radiograph absorptiometry. Treatment has focused on oral contraceptive use, yet improved bone mineral density is marked by nutritional recovery and anovulation reversal. Therefore, resolving the nutrition deficiency should be the cornerstone of treatment. Cognitive-behavioral therapy aims for weight recovery, which can lead to reversal of amenorrhea and improvement in other associated metabolic abnormalities. During treatment, estradiol levels can be followed to assess hypothalamic-pituitary-ovarian recovery because estradiol secretion may increase well before ovulation occurs. In patients failing the above interventions, hormone replacement should be considered, but bone mineral density should be followed because patients may continue to lose bone despite treatment with oral contraceptives if nutrition is not improved.

The Female Athlete Triad

The female athlete triad (Triad) refers to the interrelationships among energy availability, menstrual function, and bone mineral density, which may have clinical manifestations including eating disorders, functional hypothalamic amenorrhea, and osteoporosis. With proper nutrition, these same relationships promote robust health. Athletes are distributed along a spectrum between health and disease, and those at the pathological end may not exhibit all these clinical conditions simultaneously. Energy availability is defined as dietary energy intake minus exercise energy expenditure. Low energy availability appears to be the factor that impairs reproductive and skeletal health in the Triad, and it may be inadvertent, intentional, or psychopathological. Most effects appear to occur below an energy availability of 30 kcal.kg(-1) of fat-free mass per day. Restrictive eating behaviors practiced by girls and women in sports or physical activities that emphasize leanness are of special concern. For prevention and early intervention, education of athletes, parents, coaches, trainers, judges, and administrators is a priority. Athletes should be assessed for the Triad at the preparticipation physical and/or annual health screening exam, and whenever an athlete presents with any of the Triad's clinical conditions. Sport administrators should also consider rule changes to discourage unhealthy weight loss practices. A multidisciplinary treatment team should include a physician or other health-care professional, a registered dietitian, and, for athletes with eating disorders, a mental health practitioner. Additional valuable team members may include a certified athletic trainer, an exercise physiologist, and the athlete's coach, parents and other family members. The first aim of treatment for any Triad component is to increase energy availability by increasing energy intake and/or reducing exercise energy expenditure. Nutrition counseling and monitoring are sufficient interventions for many athletes, but eating disorders warrant psychotherapy. Athletes with eating disorders should be required to meet established criteria to continue exercising, and their training and competition may need to be modified. No pharmacological agent adequately restores bone loss or corrects metabolic abnormalities that impair health and performance in athletes with functional hypothalamic amenorrhea.

Whole-body vibration can reduce calciuria induced by high protein intakes and may counteract bone resorption: A preliminary study

Excess protein intake can adversely affect the bone via an increase in calcium excretion, while suitable mechanical loading promotes osteogenesis. We therefore investigated whether vibration exposure could alleviate the bone mineral losses associated with a metabolic acidosis. Ten healthy individuals aged 22 - 29 years (median = 25) underwent three 5-day study periods while monitoring their dietary intake. The study consisted of recording the participants' usual dietary intake for 5 consecutive days. Participants were then randomly divided into two groups, one of which received a protein supplement (2 g x kg(-1) body mass x day(-1); n = 5) and the other whole-body low-magnitude (3.5 g), low-frequency (30 Hz) mechanical vibration (WBV) delivered through a specially designed vibrating plate for 10 min each day (n = 5). Finally, for the third treatment period, all participants consumed the protein supplement added to their normal diet and were exposed to WBV exercise for 10 min per day. Daily urine samples were collected throughout the experimental periods to determine the excretion of calcium, phosphate, titratable acid, urea, and C-telopeptide. As expected, when the participants underwent the high protein intake, there was an increase in urinary excretion rates of calcium (P < 0.001), phosphate (P < 0.003), urea (P < 0.001), titratable acid (P < 0.001), and C-telopeptide (P < 0.05) compared with baseline values. However, high protein intake coupled with vibration stimulation resulted in a significant reduction in urinary calcium (P = 0.006), phosphate excretion (P = 0.021), and C-telopeptide (P < 0.05) compared with protein intake alone, but did not affect titratable acid and urea output. The participants showed no effect of WBV exercise alone on urinary excretion of calcium, phosphate, urea, titratable acid, or C-telopeptide. The results indicate that vibration stimulation can moderate the increase in bone resorption and reduction in bone formation caused by a metabolic acidosis.

Menstrual disorders in athletes

The various menstrual disorders in athletes may reflect different degrees of exposure to a disrupting factor or differences in the susceptibility of various women to disruption. The incidences of these disorders are not well documented, but they appear to be highest in aesthetic, endurance and weight-class sports, and at younger ages, higher training volumes and lower bodyweights. The morbid effects of these disorders include infertility, low bone mass, impaired endothelium-dependent vasodilation, and impaired skeletal muscle oxidative metabolism. The high incidences of menstrual disorders in athletes may derive in part from the self-selection of extraneously affected women into athletics, but many women acquire their menstrual disorders in athletics by failing to adequately increase dietary energy intake in compensation for exercise energy expenditure. Applied research is needed to develop effective dietary interventions that are acceptable to athletes.

The effect of stress on menstrual function

Historically difficult to define, stress is, in one sense, the factor that stressors have in common in their impact on the body. Menstrual function is disrupted by stressors that activate the hypothalamic-pituitary-adrenal (HPA) axis; this activation is part of a catabolic response of the whole body that mobilizes metabolic fuels to meet energy demand. Functional menstrual disorders are associated with an increase in cortisol and with a broad spectrum of other symptoms of energy deficiency. Recent experiments suggest that exercise and other stressors have no disruptive effect on reproductive function beyond the impact of their energy cost on energy availability. These studies suggest that treatments for functional menstrual disorders should aim at dietary reform and that stress is simply low energy availability. Future experiments should carefully test this hypothesis.

Energy Balance, Bone Turnover, and Skeletal Health in Physically Active Individuals

Over the past 20 years, there have been a growing number of reports of low bone mineral density (BMD) or premature bone loss in individuals with a high physical activity level. These skeletal problems have been documented mainly in underweight women with amenorrhea and have often been linked to a sex hormone deficiency. However, sex hormone treatment has been shown to have limited efficacy for the prevention or treatment of low BMD in such women. Studies of bone turnover in women with sustained exercise-associated amenorrhea using metabolic markers of osteoblast activities and collagen synthesis have demonstrated an apparent reduction of bone formation that is associated with a low body mass index (BMI) and with endocrine disturbances that are characteristic of energy deficit. Comparable metabolic and endocrine disturbances have been observed in anorexic women that reverse with weight gain. Furthermore, increases of BMD accompany weight gain in both groups of women, even without a return of menses. Collectively, these observations suggest an important link between energy balance and the balance of bone turnover in women with exercise and/or diet-associated amenorrhea. Although there have been few studies that have explored relations between bone turnover, BMD, and energy balance in physically active men, there is evidence for a link between reduced bone formation and an abrupt, short-term energy deficit. Interestingly, the presence of low BMD in physically active men has not been associated with a sex hormone deficiency. This review evaluates the evidence that underlies the hypothesis that an energy deficit is instrumental in the disturbance of bone turnover that has been observed in physically active individuals.

Dose-response relationships between energy availability and bone turnover in young exercising women

To help refine nutritional guidelines for military servicewomen, we assessed bone turnover after manipulating the energy availability of 29 young women. Bone formation was impaired by less severe restrictions than that which increased bone resorption. Military servicewomen and others may need to improve their nutrition to avoid these effects.

INTRODUCTION

We determined the dose-response relationship between energy availability (defined as dietary energy intake minus exercise energy expenditure) and selected markers of bone turnover in 29 regularly menstruating, habitually sedentary, young women of normal body composition.

MATERIALS AND METHODS

For 5 days in the early follicular phase of two menstrual cycles separated by at least 2 months, subjects expended 15 kcal/kgLBM/day in supervised exercise at 70% of aerobic capacity and consumed controlled amounts of a clinical dietary product in balanced (45 kcal/kgLBM/day) and one of three restricted (either 10, 20, or 30 kcal/kgLBM/day) energy availability treatments in random order. Blood was sampled at 10-minute intervals, and urine was collected for 24 h. Samples were assayed for plasma osteocalcin (OC), serum type I procollagen carboxy-terminal propeptide (PICP), and urinary N-telopeptide (NTX).

RESULTS

NTX concentrations (p < 0.01) and indices of bone resorption/formation uncoupling (Z(NTX-OC) and Z(NTX-PICP); both p < 10(-4)) were increased by the 10 kcal/kgLBM/day treatment. OC and PICP concentrations were suppressed by all restricted energy availability treatments (all p < 0.05). PICP declined linearly (p < 10(-6)) with energy availability, whereas most of the suppression of OC occurred abruptly between 20 and 30 kcal/kgLBM/day (p < 0.05).

CONCLUSIONS

These dose-response relationships closely resembled those of particular reproductive and metabolic hormones found in the same experiment and reported previously: similar relationships were observed for NTX and estradiol; for PICP and insulin; and for OC, triiodothyronine (T3), and insulin-like growth factor (IGF)-I. The uncoupling of bone resorption and formation by severely restricted energy availability, if left to continue, may lead to irreversible reductions in BMD, and the suppression of bone formation by less severe restrictions may prevent young women from achieving their genetic potential for peak bone mass. More prolonged experiments are needed to determine the dose-response relationships between chronic restrictions of energy availability and bone turnover.

Annual Changes of Bone Density over 12 Years in an Amenorrheic Athlete

PURPOSE

To link annual changes of bone mineral density (BMD) over 12 consecutive years to pharmacological intervention and to fluctuations of body mass and body composition in an amenorrheic athlete.

METHODS

BMD of the lumbar spine (LS) and total proximal femur (PF) were measured using dual energy x-ray absorptiometry (DXA), every 11-13 months between ages 24.8 and 36.9 yr. Body composition was assessed every 3-4 yr from a whole body DXA scan. Body mass was recorded every 3 months. For the first 5 yr of study, the subject used oral contraceptives (OC). For the subsequent 7 yr, she used estradiol skin patches (EP) with oral norethisterone.

RESULTS

The first DXA scan (age 24.8 yr) revealed a low BMD at both LS and PF, with T-scores of -1.4 and -2.8, respectively. During the next 5 yr, while adhering to OC, the BMD of her LS and PF declined by 9.8% and 12.1%, respectively. Concomitantly, her body mass fell from 45.1 to 41.4 kg, her body mass index (BMI) from 16.4 to 15.0 kg.m-2, and her percent body fat from 8.3 to <4.0%. While treated with EP and norethisterone (age 29.8-33.5 yr), her LS BMD gradually increased by 9.4%, despite a further 0.8 kg decline of body mass. From age 33.8 to 36.9 yr, voluntary weight gain (2-3 kg.yr-1; total: 8.1 kg) was accompanied by an increase of her PF BMD (16.9%), with no further increase at the LS.

CONCLUSION

Changes of BMD at the total proximal femur reflected changes of body mass in this subject. At the lumbar spine, BMD declined with weight loss but increased in association with transdermal estradiol treatment in the absence of weight gain.

The assessment of bone metabolism in female elite endurance athletes by biochemical bone markers

Purpose: Premature osteoporosis is a frequent problem in female athletes. Current concepts suggest that a disruption of the hypothalamic-pituitary axis leads to hypoestrogenism, which then causes amenorrhea and osteoporosis. However, the underlying mechanisms have been insufficiently investigated. Osteoprotegerin (OPG) and soluble TNF-α receptor antagonist ligand (sRANKL) regulate the balance of osteoblasts and osteoclasts. Their role in the pathogenesis of osteoporosis in female athletes has not been studied yet.

Methods: We measured OPG and sRANKL in relation to biochemical bone markers [osteocalcin (OC), bone alkaline phosphatase (BAP), serum β-crosslaps (CTx)] and female sex hormones [estradiol (E2) and luteinizing hormone (LH)] in fastening blood samples from 25 female elite endurance athletes and 25 matched controls.

Results: Athletes exhibited significantly higher levels of the bone resorption marker CTx than controls (0.61±0.26 vs. 0.44±0.15ng/ml). OPG and sRANKL were not changed. Subgroup analysis revealed that athletes using oral contraceptives [A-OCC(−)] had significantly higher levels of CTx (0.82±0.20 vs. 0.50±0.14ng/ml), BAP [37.3 (23.2–54.4) U/l vs. 25.2 (20.3–35.6) U/l] and OPG (3.4±0.8 vs. 2.7±0.8ng/ml) than controls who did not use oral contraceptives [C-OCC(−)]. While the difference for CTx exceeded the least significant change in this marker by approximately 30%, the differences for the bone formation markers OC and BAP were close to the least significant change. In athletes using oral contraceptives [A-OCC(+)] we found no differences compared to controls.

Conclusions: A-OCC(−) athletes have increased bone turnover with a particular stimulation of bone resorption. The increased bone resorption is not accompanied by a shift of the OPG/sRANKL relationship towards an osteoclastogenic constellation. Since increased bone resorption was not detectable in A-OCC(+) athletes, it can be suggested that OCC use might protect bone health in female athletes.

Persistent osteopenia in ballet dancers with amenorrhea and delayed menarche despite hormone therapy: a longitudinal study

OBJECTIVE

To investigate the role of estrogen deprivation and replacement in amenorrheic and nonamenorrheic dancers on hormone therapy and calcium.

DESIGN

Clinical, placebo-controlled, randomized trial study.Healthy volunteers in an academic research environment.

PATIENT(S)

Fifty-five dancers (mean age: 22.0 +/- 4.6, age at menarche: 14.7 +/- 2.3 years), including 24 amenorrheics.

INTERVENTION(S)

Amenorrheics were randomized in a controlled trial to receive placebo or Premarin, 0.625 mg for 25 days monthly, with Provera, 10 mg, for 10 of these 25 days (hormone therapy) for 2 years. These women were compared to normally menstruating controls. The study participants also received 1250 mg of calcium per day.

MAIN OUTCOME MEASURE(S)

Bone mineral density (BMD) measured at the foot, wrist, and lumbar spine. Our overall results showed no difference in BMD between the treated or placebo groups, indicating that hormone therapy did not change or normalize BMD when compared to normals. Five patients (all on placebo) who resumed menses during the study showed an increase in BMD without normalization.

CONCLUSION(S)

These findings suggest that mechanisms other than hypoestrogenism may be involved with the osteopenia associated with exercise-induced amenorrhea.

Effects of a triphasic combination oral contraceptive containing norgestimate/ethinyl estradiol on biochemical markers of bone metabolism in young women with osteopenia secondary to hypothalamic amenorrhea

This multicenter, double-blind, placebo-controlled, randomized study of 45 patients evaluated the short-term effects of an oral contraceptive [Ortho Tri-Cyclen, 180-250 micro g of norgestimate (NGM) and 35 microg of ethinyl estradiol (EE)] on biochemical markers of bone resorption, formation, and osteoprotegerin in young women (mean age +/- SD, 26.5 +/- 6.3 yr) with hypothalamic amenorrhea and osteopenia. Body fat, endocrine, and cognitive function were evaluated as secondary endpoints. Biomarkers of bone metabolism were measured at baseline and after three cycles of NGM/EE or placebo. There were significant decreases in mean values of N-telopeptide [mean (SD), -13.4 (13.4) vs. 1.2 (23.8) nmol bone collagen equivalents (BCE)/mmol creatinine (Cr); P = 0.001] and deoxypyridinoline [-1.2 (2.9) vs. -0.5 (1.5) nmol deoxypyridinoline/mmol Cr; P = 0.021] as well as significant decreases in bone specific alkaline phosphatase [-5.1 (3.5) vs. 0.4 (3.1) ng/ml; P < 0.001], osteocalcin [-5.9 (3.6) vs. -2.9 (3.7); P = 0.016], and procollagen of type I propeptide [-35.2 (44.6) vs. -0.2 (30.0) ng/ml; P = 0.025], but not osteoprotegerin [0.39 (1.46) vs. -0.2 (0.49) pmol/liter; P = 0.397] in the NGM/EE vs. placebo group. There were no significant differences between groups with respect to changes in cognitive function, mood, body weight, body mass index, body fat, percentage of body fat, and all endocrine levels except FSH, [-3.7 (3.8) vs. -0.6 (2.1) IU/liter; P < 0.001, NGM/EE vs. placebo]. No serious adverse events were reported in either group. These results suggest that NGM/EE decreases bone turnover in osteopenic premenopausal women with hypothalamic amenorrhea. Further studies are needed to determine whether estrogen will increase bone density in this population.

Aetiology of rib stress fractures in rowers

Rib stress fractures are a common and significant problem in the rowing population. They occur in approximately 6.1 to 12% of rowers and account for the most time lost from on-water training and competition. This review discusses possible causative factors for rib stress fractures in rowers. Central to the establishment of causative factors is the identification that each rib forms part of a closed ring of bone that is completed anteriorly by the sternum and posteriorly by the thoracic vertebrae. Because of the shared sternum anteriorly each ring of bone is mechanically connected. Subsequently, during rowing individual ribs are not loaded in isolation, rather the rib cage is loaded as a complete unit. Incorporating this functioning as a complete unit a possible mechanism by which different factors contribute to rib stress fracture can be developed. In rowing, muscle factors generate loading of the rib cage. The characteristics of this loading stimulus are influenced by equipment, technique and joint factors. Rib-cage loading generates bone strain in individual ribs with the response of each rib depending upon site-specific skeletal factors. Depending on the characteristics of the bone strain in terms of the magnitude and rate of strain, microdamage may develop. The bone response to this microdamage is reparative remodelling. Whether this response is capable of repairing the damage to prevent progression to a stress fracture is dependent upon training and gender factors. Identification of these factors will generate a better understanding of the aetiology of this injury, which is required for improved prevention and treatment strategies.

Exercise-associated amenorrhea: are altered leptin levels an early warning sign?

Although the exact cause of the female athlete triad (amenorrhea, disordered eating, and osteoporosis) is unknown, recent research implicates leptin, a hormone that is secreted by adipocytes. Leptin may be an important indicator of nutritional status and may also play a role in reproductive function. Physicians who develop a plan for early recognition and treatment of exercise-induced amenorrhea now may prevent the more serious consequences of osteopenia and osteoporosis later.

Bone density and amenorrhea in ballet dancers are related to a decreased resting metabolic rate and lower leptin levels

Osteopenia, which is correlated with amenorrhea and poor nutritional habits, has been well documented in elite ballet dancers. Estrogen replacement therapy and recovery from amenorrhea have not been associated with normalization of bone density. Thus, the osteopenia may be related to changes brought about by chronic dieting or other factors, such as a hypometabolic state induced by poor nutrition. The purpose of this study was to investigate the relationship of chronic dieting and resting metabolic rate (RMR) to amenorrhea and bone density. RMR, bone density, eating disorder assessments, leptin levels, and complete menstrual and medical histories were determined in 21 elite ballet dancers and in 27 nondancers (age, 20-30 yr). No significant correlations were found between high EAT26 scores, a measure of disordered eating, and RMR, bone densities, body weight, body fat, or fat-free mass. However, when RMR was adjusted for fat-free mass (FFM), a significant positive correlation was found between RMR/FFM and bone density in both the arms (P < 0.001) and spine (P < 0.05) in ballet dancers, but not in the normal controls. The dancers also demonstrated significantly higher EAT scores (22.9 +/- 10.3 vs. 4.1 +/- 2.4; P < 0.001) and lower RMR/FFM ratios (30.0 +/- 2.2 vs. 32.05 +/- 2.8; P < 0.01). The only variable to predict lower RMR/FFM in the entire sample was ever having had amenorrhea; this group had significantly higher EAT scores (18.0 +/- 13.5 vs. 10.3 +/- 10.2; P < 0.05), lower leptin levels (4.03 +/- 0.625 vs. 7.10 +/- 4.052; P < 0.05), and lower bone mineral density in the spine (0.984 +/- 0.11 vs. 1.10 +/- 0.13; P < 0.05) and arm (0.773 +/- 0.99 vs. 0.818 +/- 0.01; P < 0.05). We hypothesize that the correlation between low RMR and lower leptin levels and bone density may be more strongly related to nutritional habits in ballet dancers, causing significant depression of RMR, particularly for those with a history of amenorrhea.

Hypothalamic amenorrhea. The effects of environmental stresses on the reproductive system: a central effect of the central nervous system

Although the treatment of anovulation has become significantly more specialized and complex in the centuries since Hippocrates, a complete understanding of the causes and mechanisms of hypothalamic amenorrhea has not been achieved. Even the best research on hypothalamic amenorrhea is plagued by the lack of longitudinal studies, the use of different exercise models, the difficulty of controlling for caloric intake, and the fact that genetics may have a role in the disorder. Continuing research on metabolic rate, leptin, and other factors will ultimately answer many of the outstanding questions and will help to create better tools for treating this disorder.

The female athlete

Over the past 30 years, the number of women participating in organized sports has grown dramatically. Several forms of menstrual irregularities have been described in the female athlete: primary and secondary amenorrhoea, oligomenorrhoea, short luteal phases and anovulation. The incidence of menstrual irregularities is much higher in activities where a thin body is required for better performance. The hormonal pattern seen in these athletes is a hypothalamic amenorrhoea profile. There appears to be a decrease in gonadotrophin-releasing hormone (GnRH) pulses from the hypothalamus, which in turn decreases the pulsatile secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) and shuts down stimulation of ovary. Recently, another type of amenorrhoea has been described in swimmers which is characterized by mild hyperandrogenism. Athletes with low weight are at risk of developing the female athletic triad, which includes amenorrhoea, osteoporosis and disordered eating. Athletes with this triad are susceptible to stress fractures. Other issues include the pregnant athlete. Intensive exercise during pregnancy can cause bradycardia. Safe limits of aerobic exercise in pregnancy depend on previous exercise habits. Infertility, which may develop with exercise, is probably reversible with reduction of exercise or weight gain. High impact sports activities may produce urinary incontinence. Oestrogen replacement therapy is often prescribed in amenorrhoeic athletes, but bone loss may not be completely reversible.

Responses of markers of bone and collagen turnover to exercise, growth hormone (GH) administration, and GH withdrawal in trained adult males

To examine the interactions between acute exercise and GH on markers of bone and collagen turnover and to assess the potential for detecting GH abuse in athletes using these markers, we studied 17 aerobically trained males (age, 26.9+/-1.5 yr). Sequential studies of exercise, GH administration, and GH withdrawal were undertaken. A randomized, controlled study of rest vs. exercise showed that exercise did not change serum osteocalcin; other markers of formation increased transiently (each P<0.001): bone-specific alkaline phosphatase (+16.1%), carboxyterminal propeptide of type I procollagen (+14.1%), and procollagen III N-terminal extension peptide (+5.0%). The carboxyterminal cross-linked telopeptide of type I collagen, a bone resorption marker, increased 9.7% (P = 0.018) in response to exercise. A randomized, double blind, placebo-controlled, parallel study of recombinant human GH treatment (0.15 IU/kg x day) for 1 week increased serum osteocalcin (net increase preexercise, +/-10.0%; P = 0.017), carboxyterminal propeptide of type I procollagen (+17.6%; P = 0.002), procollagen III N-terminal extension peptide (+48.4%; P = 0.001), and carboxyterminal cross-linked telopeptide of type I collagen (53.3%; P = 0.009). Disappearance half-times after cessation of recombinant human GH for pre- and postexercise markers ranged from 248-770 h. We conclude 1) endurance exercise transiently activates bone and collagen turnover; 2) brief GH administration results in similar but quantitatively greater augmentation; and 3) these data will assist in designing a GH detection strategy.

The oral contraceptive pill: a revolution for sportswomen?

OBJECTIVES

To determine the effects of the oral contraceptive pill (OCP) on skeletal health, soft tissue injury, and performance in female athletes.

METHODS

A literature review was performed using literature retrieval methods to locate relevant studies.

RESULTS

Most female athletes primarily choose to use the OCP for contraceptive purposes, but cycle manipulation and control of premenstrual symptoms are secondary advantages of its use. The effect of the OCP on bone density in normally menstruating women is unclear, with some studies reporting no effect, others a positive effect, and some even a negative effect. The OCP is often prescribed for the treatment of menstrual disturbances in female athletes, and improvements in bone density may result. Whether the OCP influences the risk of stress fracture and soft tissue injuries is not clear from research to date. Effects of the OCP on performance are particularly relevant for elite sportswomen. Although a reduction in Vo2MAX has been reported in some studies, this may not necessarily translate to impaired performance in the field. Moreover, some studies claim that the OCP may well enhance performance by reducing premenstrual symptoms and menstrual blood loss. A fear of weight gain with the use of the OCP is not well founded, as population studies report no effect on weight, particularly with the lower dose pills currently available.

CONCLUSIONS

Overall, the advantages of the pill for sportswomen would appear to outweigh any potential disadvantages. Nevertheless, there is individual variation in response to the OCP and these should be taken into account and monitored in the clinical situation. Women should be counselled as to the range of potential benefits and disadvantages in order to make an informed decision based on individual circumstances.