- THE CAUSES OF DELAYED MENARCHE IN FEMALE ATHLETES - INTRODUCTION Greater emphases on the benefits of exercise have led to a greater participation of women in sport at all levels. Exercise has been promoted, endorsed and encouraged in the medical community as a way to reduce stress and maintain a healthy lifestyle. While moderate exercise does provide valuable benefits, intensive exercise associated with elite female athletes poses serious health risks to the female body. The female reproductive system is very intricate and highly sensitive to physiological stress. This increased stress level is often associated with several reproductive abnormalities such as delayed menarche, primary and secondary amenorrhea and oligomenorrhea occurring in 6-79% of women engaged in athletic activity (Warren and Perlroth 2001).
This wide range of percentages is a result of various levels of athletic discipline and level of competition (Abraham et al. 1982, Glass et al. 1987). The aforementioned reproductive abnormalities are largely the result of hypothalamic dysfunction and disturbance of the gonadotropin-releasing hormone (GnRH) pulse generator. This suppression of GnRH results in possible infertility and an irreversible decrease in bone density. The scientific community seems to be split however, on the specific trigger that causes the reproductive dysfunction in athletes.
There are two theories, which are widely accepted, the body composition theory and the energy drain theory. The body composition theory states that intensive athletic training activates the hypothalamic-pituitary-adrenal axis, which disrupts GnRH pulsatility and hence menstrual function. It is theorized that this suppression of the menstrual cycle may be a physiological adaptation to low caloric intake (Warren 1980). There is much evidence that suggests that the hormone leptin may help regulate reproductive function. Leptin levels have been found to change with respect to fat stores and energy availability.
So, it can be reasoned that a low caloric intake will result in low levels of leptin. A study of females showed that had there is a certain threshold level of leptin that when gone below will result in no menstrual cycle (Kopp et al. 1997). Leptin receptors have also been located on hypothalamic control of the GnRH pulse generator thus leptin may be a critical factor involved in signaling low energy availability to the reproductive axis (Warren and Perlroth 2001). This shows us that the body can adapt to low energy levels by halting reproductive function and using the resulting energy for other metabolic activities. The second view is the energy drain theory, which accounts for the loss of reproductive function in all athletic disciplines instead of just the "lean" sports.
Athletes that participate in swimming and rowing for example are often muscle bound and of average to above average weight but they are equally susceptible to menstrual irregularities. The difference in these two types of athletes according to a study done by Warren and Perlroth (2001) is that athletes engaged in these sports are characterized by mildly elevated LH levels, elevated LH / FSH ratios and mild hyperandrogenism rather than the hypoestrogenism observed in athletes engaged in sports requiring thinness. The results of these factors are an increase in androgen levels and an inhibitory effect on the female reproductive system. These effects are not as widely studied and there is limited data on them.
Delayed menarche in female athletes has many clinical consequences. Low LH, FSH and thelarche levels found in pre-pubertal ballet dancers may cause a prolonged pre-pubertal stage. This delay of puberty has been shown to be directly related to the activity level of the athlete (Warren 1980). As the female becomes more heavily involved in strenuous exercise the frequency of pre-pubertal delay increase thus showing that pubertal progression may be related to the energy drain that elite athletes encounter (Warren and Perlroth 2001).