Hormonal and metabolic imbalance Eumenorrhea is defined as regular cycles occurring at intervals between 21 and 35 days. In adolescents, the cycles range between 21 and 45 days.19 defined as no menarche by age 15 years.20 Primary amenorrhoea is Secondary amenorrhoea refers to an absence of three consecutive cycles post-menarche. Oligomenorrhea is defined as a cycle length greater than 45 days. Estimates of the prevalence of menstrual disorders in athletes vary widely.21 Secondary amenorrhoea prevalence is estimated in collegiate women from 2% to 5% and as high as 69% in dancers22 and 65% in long-distance runners.23 Primary amenorrhoea in collegiate athletes was found to be 7% overall, and was higher (22%) in cheerleading, diving and gymnastics.24 Subtle menstrual dysfunction, such as very light bleeding, mildly extended menstrual interval and premenstrual and postmenstrual spotting may occur, and may be underestimated by routine screening.25 Abnormal levels of hormones,26 LH pulsatility, inadequate body fat stores, low EA and exercise stress may be aetiological factors in menstrual disorders in athletes. Marked reduction in EA may disrupt the LH pulsatility by affecting the hypothalamic hormone gonadotropin-releasing hormone output27 which subsequently alters the menstrual cycle. This is known as Functional Hypothalamic Amenorrhea (FHA). Rapid or significant fat mass reduction, even over as short as a 1-month period, may compromise menstrual function. Low EA alters levels of metabolic hormones and substrates, for example, insulin, cortisol, growth hormone, insulin-like growth factor-I (IGF-I), 3,3,5-triiodothyronine, grehlin, leptin, peptide tyrosine– tyrosine, glucose, fatty acids and ketones.28 Health and performance consequences of RED-S RED-S can have serious implications for many body systems, resulting in short-term and long-term compromise of optimal health and performance. Athletes who suffer from long-term low EA may develop nutrient deficiencies (including anaemia), chronic fatigue and increased risk of infections and illnesses, all of which have the potential to harm health and performance.6 Physiological and medical complications involve the cardiovascular, gastrointestinal, endocrine, reproductive, skeletal, renal and central nervous systems.6 Psychological stress and/or depression can result in low EA and EDs and can also be a result of low EA.17 Research indicates that muscle protein synthesis is reduced even at EA of 30 kcal/ kg FFM/day.29 Low EA causes unfavourable lipid profiles and endothelial dysfunction, thereby increasing cardiovascular risk.30 Hormonal and metabolic abnormalities caused by RED-S and carbohydrate deficiency can result in a reduction in glucose utilisation, mobilisation of fat stores, slowing of metabolic rate and a decreased production of growth hormone.31 Irregular or absent menses may have significant emotional impact creating anxiety and an altered perception of selfnormalcy.32 It may also confound conception, leading to unexpected pregnancy as well as inaccurate dating of pregnancy. Long-term reproductive repercussions of RED-S for women and men are unknown. RED-S also has adverse health consequences for bone. Peak bone mass occurs around 19 years in women and 20.5 years in men.33 and deposition into bone, while progesterone facilitates the actions of oestrogen through multiple complex mechanisms.34 Even silent oestrogen/progesterone imbalance, as seen in subclinical ovulatory disturbances with low EA may produce negative changes in bone.35 In men and women, testosterone has anabolic effects on bone, stimulating osteoclasts and increasing bone formation and calcium absorption.36 with low BMD in male athletes.37 Endogenous oestrogens and androgens have independent effects on bone development in both sexes.38,39 the stress hormones, catecholamines and cortisol, concomitant with low EA, have a negative effect.40 The bones of athletes with chronic amenorrhoea, benefit less from the osteogenic effects of exercise.41 attributed to hypoestrogenism of menstrual dysfunction, low EA is now recognised as an independent factor of poor bone health at all levels of energy deficiency due to decreased IgF-1 and bone formation markers levels.42 Although low BMD was first Low-testosterone levels have been associated Increases in Oestrogen increases uptake of calcium into blood Bone loss in these athletes may be irreversible.43 Changes in bone structure lead to an increased risk of stress fractures.44 fractures in both sexes.45,46 menstrual dysfunction,47 poor bone health48,49 and eating psychopathology.49–51 Dietary insufficiencies increase the risk of stress Additional risk factors include compulsive exercise, underlying low body mass index, prior fracture50 High-risk stress fractures (ie, femoral neck) occur in adolescent athletes with the RED-S, and can have serious long-term consequences52,53 (figure 1). RED-S can also affect athletic performance. Functional impairments associated with low energy availability include a greater prevalence of viral illnesses,55 injuries56 and most critically reduced responsiveness to training and subsequent performance.57 Further studies of performance nummer 4 | september 2014 | Sport & Geneeskunde 17 Pagina 16
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