Altered Hypothalamic-Pituitary-Ovarian Axis Function in Young Female Athletes

Glucocorticoids and Their Receptor Isoforms: Roles in Female Reproduction, Pregnancy, and Foetal Development

Alterations in the hypothalamic-pituitary-adrenal (HPA) axis and associated changes in circulating levels of glucocorticoids are integral to an organism's response to stressful stimuli. Glucocorticoids acting via glucocorticoid receptors (GRs) play a role in fertility, reproduction, placental function, and foetal development. GRs are ubiquitously expressed throughout the female reproductive system and regulate normal reproductive function. Stress-induced glucocorticoids have been shown to inhibit reproduction and affect female gonadal function by suppressing the hypothalamic-pituitary-gonadal (HPG) axis at each level. Furthermore, during pregnancy, a mother's exposure to prenatal stress or external glucocorticoids can result in long-lasting alterations to the foetal HPA and neuroendocrine function. Several GR isoforms generated via alternative splicing or translation initiation from the GR gene have been identified in the mammalian ovary and uterus. The GR isoforms identified include the splice variants, GRα and GRβ, and GRγ and GR-P. Glucocorticoids can exert both stimulatory and inhibitory effects and both pro- and anti-inflammatory functions in the ovary, in vitro. In the placenta, thirteen GR isoforms have been identified in humans, guinea pigs, sheep, rats, and mice, indicating they are conserved across species and may be important in mediating a differential response to stress. Distinctive responses to glucocorticoids, differential birth outcomes in pregnancy complications, and sex-based variations in the response to stress could all potentially be dependent on a particular GR expression pattern. This comprehensive review provides an overview of the structure and function of the GR in relation to female fertility and reproduction and discusses the changes in the GR and glucocorticoid signalling during pregnancy. To generate this overview, an extensive non-systematic literature search was conducted across multiple databases, including PubMed, Web of Science, and Google Scholar, with a focus on original research articles, meta-analyses, and previous review papers addressing the subject. This review integrates the current understanding of GR variants and their roles in glucocorticoid signalling, reproduction, placental function, and foetal growth.

Neuroendocrine Blockade of the Reproductive Axis in Female Athletes

This review aims at defining the neuroendocrine mechanisms underlying the sport-induced restrictions of the reproductive axis in female athletes. Episodic gonadotropin release was found to be compromised, presumably a result of impaired hypothalamic pulsatile GnRH release. Any deviation from optimal gonadotropin release may result in a suboptimal function of the ovaries, leading to disorders of the menstrual cycle and ovulation. A whole spectrum of menstrual dysfunctions ranging from ovulatory eumenorrhea to luteal phase defects and amenorrhea has been reported in sportive women. As essential neuroendocrine factors underlying these observations, activation of the adrenal axis and altered central nervous neurotransmitter activity have been identified to transfer metabolic, nutritional, and stress signals into the hypothalamic GnRH release. The degree by which the neuroendocrine axis governing reproduction is impaired critically depends on the intensity and duration of exercise and the state of training. Other decisive factors may be energy expenditure and availability, nutritional components, and the maturity of the hypothalamic-pituitary-ovarian (HPO) axis when sport activity was initiated. In conclusion, the gradual cessation of reproductive function observed in female athletes may be interpreted as an adaptive mechanism in response to physical and psychological endurance during sport. This sport-induced restriction of reproductive capacity may serve as protection (endogenous contraception) to preserve a woman’s health.

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.

Morphological and molecular variations induce mitochondrial dysfunction as a possible underlying mechanism of athletic amenorrhea

Female athletes may experience difficulties in achieving pregnancy due to athletic amenorrhea (AA); however, the underlying mechanisms of AA remain unknown. The present study focuses on the mitochondrial alteration and its function in detecting the possible mechanism of AA. An AA rat model was established by excessive swimming. Hematoxylin and eosin staining, and transmission electron microscopic methods were performed to evaluate the morphological changes of the ovary, immunohistochemical examinations and radioimmunoassays were used to detect the reproductive hormones and corresponding receptors. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to test the mtDNA copy number. PCR and western blot analysis were used to test the expression of ND2. The change of morphological features of the rat ovaries revealed evident abnormalities. Particularly, the features of the mitochondria were markedly altered. In addition, reproductive hormones in the serum and tissues of AA rats were also detected to evaluate the function of the ovaries, and the levels of these hormones were significantly decreased. Furthermore, the mitochondrial DNA copy number (mtDNA) and expression of NADH dehydrogenase subunit 2 (ND2) were quantitated by qPCR or western blot analysis. Accordingly, the mtDNA copy number and expression of ND2 expression were markedly reduced in the AA rats. In conclusion, mitochondrial dysfunction in AA may affect the cellular energy supply and, therefore, result in dysfunction of the ovary. Thus, mitochondrial dysfunction may be considered as a possible underlying mechanism for the occurrence of AA.

Mechanisms of arsenic disruption on gonadal, adrenal and thyroid endocrine systems in humans: A review

Due to its toxicity as a carcinogen and wide distribution in the environment, arsenic (As) exposure in humans is of public concern globally. Many studies have manifested that As exposure induces cancers besides pathological effects in humans. Animal studies showed that chronic As exposure induces serious neurological effects. Based on recent studies, researchers proposed that As, including arsenate (AsV) and arsenite (AsIII), is also an endocrine disruptor. This review discusses the mechanisms of As toxicity on three endocrine systems including gonadal, adrenal and thyroid endocrine systems. Arsenic methylation and oxidative stress are responsible for As-induced disorders of endocrine systems, however, strong binding of AsIII to thiols also play an important role. Some studies showed AsV toxicity on endocrine systems, but mechanistic investigation is lacking. Research is needed to look into their toxicity mechanisms to help cure the illnesses caused by As-induced endocrine system disorders.

Prevalence and associated factors of Osgood-Schlatter syndrome in a population-based sample of Brazilian adolescents

BACKGROUND

Osgood-Schlatter (OS) syndrome is a disease of the musculoskeletal system often observed during the bone growth phase in adolescents. HYPOTHESIS/ PURPOSE: Demographic and anthropometric factors and those linked to the practice of sports may be related to the prevalence of OS. The aim of the present study was to describe the epidemiologic profile and associated factors of individuals with OS syndrome in a population-based sample of Brazilian adolescents.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A cross-sectional study was conducted with 956 adolescent students (474 boys, 482 girls) from 2008 to 2009 enrolled in the school system of Natal, Brazil. The age ranged between 12 and 15 years (13.7 ± 1.04 years). Tests were performed to assess the anthropometric and clinical aspects related to OS. To confirm the diagnosis of OS syndrome, the participant had to fulfill all the following clinical criteria: pain with direct pressure on the tibial apophysis; aforementioned pain before, during, and after physical activities; enlargement or prominence of the tibial apophysis; pain with resisted knee extension; and pain from jumping.

RESULTS

The prevalence of OS in the sample was 9.8% (11.0% of boys and 8.3% of girls; boys, 13.5 ± 1.07 years; girls, 13.6 ± 1.01 years). The results showed that 74.6% of the students suffered from muscle shortening. Multivariate analysis using logistic regression showed that the factors associated with the presence of OS were the regular practice of sport activity (odds ratio, 1.94; 95% confidence interval, 1.22-3.10) and the shortening of the rectus femoris muscle (odds ratio, 7.15; 95% confidence interval, 2.86-17.86).

CONCLUSIONS

The regular practice of sports in the pubertal phase and the shortening of the rectus femoris muscle were the main factors associated to the presence of OS syndrome in the students.

Relações entre leptina, puberdade e exercício no sexo feminino

O processo de puberdade feminina envolve vários fenômenos anatômico-fisiológicos, sendo o acontecimento da menarca o indicador da maturidade sexual feminina. A idade média de menarca gira em torno de 12 anos. Para meninas atletas, a menarca pode ocorrer mais tarde, e dependendo do estresse causado pelo exercício, pode resultar em um quadro de amenorreia hipotalâmica. O hormônio leptina, além de apresentar relação com a obesidade, também tem relação com o sistema reprodutor. Os estudos mais recentes em humanos demonstram existir relações importantes entre as concentrações de leptina plasmática e o processo de puberdade feminino. Este estudo teve por objetivo verificar a influência da leptina no processo pubertário feminino relacionado com exercício, do ponto de vista fisiológico, por meio de uma pesquisa de revisão bibliográfica. Os resultados das pesquisas apresentadas demonstram que o aumento de leptina sanguínea foi relatado como tendo correlação inversamente proporcional à idade de menarca. Além disso, verificou-se que a leptina tem correlação inversa com o exercício físico; as baixas concentrações de leptina plasmática estão diretamente ligadas à desregulação do sistema reprodutor em mulheres atletas. Conclui-se que a leptina relaciona-se com o sistema reprodutor feminino, fato que fica evidente durante o processo de puberdade. Já em meninas e mulheres atletas, as concentrações de leptina encontradas foram inferiores às daquelas não-atletas, demonstrando a relação tecido adiposo/leptina/sistema reprodutor/exercício.

Strategies used by physical therapists in the U.S. for treatment and prevention of the female athlete triad

OBJECTIVE

To describe current methods of treatment and prevention used by physical therapists in the United States (US) for the female athlete triad.

DESIGN

Descriptive analysis.

SETTING

Physical therapists currently practicing in the U.S.

PARTICIPANTS

500 American Physical Therapy Association members.

MAIN OUTCOME MEASURES

A survey was used to assess methods of practice for detecting, treating, and preventing the female athlete triad. Descriptive statistics summarized demographics about the survey participants. Likert scales and narrative descriptors determined the likelihood and frequency of employing certain treatment and prevention methods.

RESULTS

Participants included 205 physical therapists for a 41% (205/500) response rate. Twenty-six percent (54/205) of the respondents used specific treatment methods, including education, for the female athlete triad; 48% of these respondents (26/54) incorporated preventative strategies other than screening; 13/54 (24%) assisted in athletic screening for the triad disorders. Physical therapists are more likely to talk to the athlete, the athlete's parents, and physicians when triad symptoms are suspected. The frequencies in which specific treatment and prevention strategies are utilized have been described.

CONCLUSIONS

Physical therapists must be responsible for recognizing, treating and preventing the female athlete triad. This study emphasizes that there is a greater need for knowledge regarding the triad to be incorporated into physical therapy curriculums, continuing education programs and professional practice.

Impacto da atividade física e esportes sobre o crescimento e puberdade de crianças e adolescentes

OBJETIVO: Apresentar revisão atualizada e crítica sobre o impacto do esporte e da atividade física no crescimento, desenvolvimento puberal e mineralização óssea de crianças e adolescentes. FONTES DE DADOS: Pesquisa bibliográfica nos bancos de dados Medline e Lilacs (1987-2007), selecionando os artigos escritos em inglês, português ou espanhol, a partir dos descritores "esportes" e "exercícios", em combinação com "crescimento", "puberdade" e "mineralização óssea". Foram examinados 252 artigos e 48 deles selecionados. SÍNTESE DOS DADOS: Diferentes modalidades esportivas não aumentam ou diminuem a estatura. Ocorre um viés de seleção, no qual fatores constitucionais determinam a seleção de biótipos privilegiados para determinados esportes. O exercício físico leve a moderado estimula o crescimento e deve ser incentivado. A atividade física extenuante, principalmente quando associada à restrição dietética, afeta o crescimento, o desenvolvimento puberal, a função reprodutiva e a mineralização óssea. A musculação praticada por jovens pré-púberes pode ser prejudicial, se não for realizada sob supervisão, já que há um potencial risco de lesão na cartilagem de crescimento. Entretanto, quando bem supervisionada, pode levar a um aumento de força e resistência muscular. CONCLUSÕES: Os efeitos deletérios dos esportes sobre o crescimento e desenvolvimento só foram observados em atletas de elite submetidos a treinamento intensivo e restrição alimentar. Alterações hormonais e de citocinas inflamatórias são parte da fisiopatologia desse processo. É necessário que estudos longitudinais avaliem as repercussões da atividade física recreacional sobre a estatura final.

Bone metabolism in adolescent boys with anorexia nervosa

BACKGROUND

Anorexia nervosa (AN) is a condition of severe undernutrition associated with low bone mineral density (BMD) in adolescent females with this disorder. Although primarily a disease in females, AN is increasingly being recognized in males. However, there are few or no data regarding BMD, bone turnover markers or their predictors in adolescent AN boys.

HYPOTHESES

We hypothesized that BMD would be low in adolescent boys with AN compared with controls associated with a decrease in bone turnover markers, and that the gonadal steroids, testosterone and estradiol, and levels of IGF-I and the appetite regulatory hormones leptin, ghrelin, and peptide YY would predict BMD and bone turnover markers.

METHODS

We assessed BMD using dual-energy x-ray absorptiometry and measured fasting testosterone, estradiol, IGF-I, leptin, ghrelin, and peptide YY and a bone formation (aminoterminal propeptide of type 1 procollagen) and bone resorption (N-telopeptide of type 1 collagen) marker in 17 AN boys and 17 controls 12-19 yr old.

RESULTS

Boys with AN had lower BMD and corresponding Z-scores at the spine, hip, femoral neck, trochanter, intertrochanteric region, and whole body, compared with controls. Height-adjusted measures (lumbar bone mineral apparent density and whole body bone mineral content/height) were also lower. Bone formation and resorption markers were reduced in AN, indicating decreased bone turnover. Testosterone and lean mass predicted BMD. IGF-I was an important predictor of bone turnover markers.

CONCLUSION

AN boys have low BMD at multiple sites associated with decreased bone turnover markers at a time when bone mass accrual is critical for attainment of peak bone mass.

Análise da evolução da carreira desportiva de nadadores do gênero feminino utilizando a modelação matemática

A performance desportiva em crianças e jovens deve sempre ter em consideração os processos de crescimento, maturação(1) e a influência na taxa de crescimento dos resultados desportivos. Nesse âmbito, com este estudo, procuramos estudar a taxa de crescimento dos resultados desportivos desde a formação até à etapa de alto nível desportivo em todas as provas do calendário olímpico, tentando estabelecer relações de associação com o crescimento, maturação e treino, para as nadadoras do sexo feminino. Foi utilizada uma amostra constituída pelas nadadoras presentes nos rankings portugueses de natação durante quatro anos (1998 a 2002), num total aproximado de 6.000 dados. A taxa de crescimento dos resultados desportivos foi calculada com base no seguinte algoritmo: (tempo inicial-tempo final)/tempo inicial*100. Pela análise dos resultados relativos às taxas de crescimento (TC) dos resultados, verificamos que se verifica: (i) tendência geral da TC dos resultados aumentar dos 11 para os 12 anos e dos 14 aos 15 anos em piscina de 25m; (ii) tendência similar à verificada em piscina de 25 para a piscina de 50m, mas com tendências de crescimento superiores, quer aos 10-11 anos e 14-15 anos. Com base na análise dos resultados, concluímos que a evolução dos resultados desportivos na natação está dependente, fortemente, para além de outros, do ritmo de crescimento, desenvolvimento e maturação das nadadoras.

The effect of short-term exercise on plasma leptin levels in patients with anorexia nervosa

Plasma leptin concentrations are markedly reduced in malnourished patients with anorexia nervosa (AN). Whether the long-term underweight and low-fat stores affect the leptin response to exercise remains unknown. We investigated the effect of 45-minute cycle ergometer exercise (2 W kg-1 of lean body mass [LBM]) on plasma leptin, norepinephrine (NE), glycerol, and insulin levels in 10 patients with AN and in 15 healthy age-matched women (C). Plasma leptin levels immediately and 90 minutes after the exercise bout were significantly reduced compared with basal leptin levels in both AN and C groups (P<.05). Compared with the control trial, leptin levels were significantly lower immediately and 90 minutes after exercise in the AN group (P<.05) but not in the C group. Basal and exercise-induced plasma glycerol and NE levels did not differ significantly between the groups. Basal and exercise-induced plasma insulin levels were significantly lower in the AN group compared with the C group (P<.05). In conclusion, we demonstrated that a single bout of low-intensity exercise significantly reduces plasma leptin levels in patients with AN. In healthy women, exercise had no effect on lowering leptin concentrations beyond the diurnal decrease that occurs in the absence of exercise. Neither NE nor insulin are responsible for the different response of leptin to exercise in AN.

Mind and muscle: the cognitive-affective neuroscience of exercise

There is growing basic-science interest in the mechanisms underpinning the positive effects of exercise on brain function and cognitive-affective performance. There is also increasing clinical evidence that exercise may prevent and treat various neuropsychiatric disorders. At the same time, there is growing awareness that athletic performance is mediated in crucial ways by central nervous system mechanisms. The relevant mechanisms in all these cases requires further exploration, but likely includes neurotrophic, neuroendocrine, and neurotransmitter systems, which in turn are crucial mediators of psychopathology and resilience. The hypothesis that Homo sapiens evolved as a specialist endurance runner provides an intriguing context against which to research the proximal mechanisms relevant to a cognitive-affective neuroscience of exercise.

Effects of sports training in adolescence on growth, puberty and bone health

Athletic training in adolescent females is important for their well-being; indeed, it may have both positive and negative effects on some physiological processes, as growth, reproductive axis and bone health. Adequate physical activity likely exerts neither a positive nor a negative effect on growth. By contrast, intensive training and insufficient diet may have a negative influence on growth, probably due to energy deficiency and impairment of the growth hormone-insulin-like growth factor-I axis; net long term-effects of such alterations remain to be established. Adolescents who perform regular athletic training present with normal or slightly advanced sexual maturation, because increased strength and power associated with earlier maturation advantage them. However, intensive training and inadequate energy intake may induce delayed menarche and menstrual dysfunctions. The consequent hypoestrogenism, in association with the nutritional deficiencies, may affect bone health. On the contrary, regular physical activity increases the amount of bone mass gained during childhood and adolescence mainly at the bone sites which are trained. Since the number of adolescent females involved in strenuous sports from an early age is increasing, physicians must be aware of such effects, explain to girls and their parents the 'right' sports training and appropriate dietary regimens, and recognize problems due to excessive training as soon as possible. These issues should not be a cause of lesser involvement in athletic participation of young people.

Special Nutritional Concerns for the Female Athlete

Inadequate dietary intake is the primary nutritional concern of today's female athlete. As these athletes fail to consume enough energy to support the physical demands of training, they become at risk for disordered eating, amenorrhea, and osteoporosis, conditions collectively identified as the female athlete triad. This review addresses nutritional concerns of the female athlete, identification of those at risk, relationship of energy intake to menstrual irregularities, and recently identified chronic diseases associated with the female athlete triad. Strategies are offered to prevent harmful behaviors leading to the comorbidities associated with inadequate dietary intakes.