Factors Associated With Menstrual Irregularities and Decreased Bone Mineral Density in Female Athletes

Abstract

n intense preoccupation with leanness and low body weight exists in the athletic population. This is especially apparent in young female athletes. M'ith strong intrinsic and extrinsic pressure to perform and the need to appear lean and fit, training is often taken to extremes. Whether the athlete's goal is to improve performance, become "ultra fit," o r lose weight, the results are often similar in the female population: menstrual irregularity, namely amenorrhea. While the absence of menses may be a pleasant convenience for the female athlete, she may be completely unaware that her skeleton could suffer irreversible consequences, such as decreased peak bone mass and eventual osteoporosis (7,38). Athletic amenorrhea, also termed hypothalamic hypogonadism (23), has been shown to cause substantial decreases in bone mineral density (BMD) at various sites in the body, especially in areas of high trabecular content (10,13,14, 29,32,38,44). Unfortunately, the loss of BMD is a silent process, and the athlete is usually unaware that a problem exists until a related injury, such as a stress fracture, occurs.Numerous variables are thought to be associated with athletic amenorrhea: training intensity, hours spent training, diet, body weight, body composition, age of menarche, type of sport, and psychological stress (8, l2,29). While many authors have sought to determine the specific cause of menstrual irregularities in female athletes, n o evidence exists demonstrating that a single risk factor is responsible (32). Therefore, it is likely that all (or at least several) of these factors are working in concert and contribute to menstrual disturbance (7,12,32,40).Regardless of the cause, menstrual irregularities are common among female athletes ( 1 2-15,23). As many as 51 % of endurance runners (1 1 ), 44% of ballet dancers (5), and 12% of swimmers and cyclist3 (45) have reported menstrual disturbances during periods of training. Rutherford (44), who studied female triathletes, found that 50% of the subjects experienced menstrual disturbances. Furthermore, these women reported that "[menstrual irregularities] were representative of the general incidence among good triathletes." Although resumption of menses usually occurs following a reduction o r cessation of training (13,15,41), it is not known if the decrease in BMD is permanent and will predispose the women to stress fractures or osteope rosis (1 3,15,32,4O).In addition to the large number of variables involved in these studies, interpretation of the results is made difficult by the lack of standard definitions of menstrual categories. Criteria for amenorrhea have ranged from

Amenorréia e osteoporose em adolescentes atletas

“…O aumento deste consumo também está relacionado com alterações no metabolismo do estrógeno. Contudo, há evidências de que a ingestão de fibras entre as atletas com ou sem o sintoma são semelhantes (Fruth & Worrell, 1995). O baixo consumo de proteínas pode contribuir para o surgimento da amenorréia.…”

“…No entanto, atletas com baixo consumo de energia têm ingestão protéica inferior à daquelas com consumo energético normal. Assim, estudos mostraram que a ingestão protéica em si não possui relação com as irregularidades menstruais (Hale, 1984;Lloyd et al, 1987;Fruth & Worrell, 1995).…”

“…Caso exista algo fora do padrão, um sistema de proteção é ativado, atuando geralmente através da supressão do sistema reprodutivo e resultando na disfunção menstrual (Fruth & Worrell, 1995).…”

“…Não se tem conhecimento ao certo da prevalência de baixa quantidade de massa óssea em atletas, mas sabe-se que naquelas com AME essa quantidade é inferior em relação àquelas com ciclos menstruais regulares (Fruth & Worrell, 1995).…”

“…Assim, as mulheres que menstruaram mais cedo foram expostas mais cedo ao hormônio e atingiram o pico de FO, ao contrário daquelas com atraso na menarca ou com amenorréia, as quais foram expostas por menos tempo ao estrógeno, diminuindo a massa óssea e aumentando o risco de desenvolver a doença (Fruth & Worrell, 1995). Conforme relataram Nguyen et al (1995), a duração de exposição ao estrógeno, somando os anos de ciclo menstrual regular e a terapia hormonal pós-menopausa, se associava a aumento da massa óssea e a redução de fraturas.…”