Final answer:
Low energy availability in girls can lead to shifts in energy allocation from reproduction to survival, resulting in hormonal imbalances within the endocrine system that can cause infertility. Conditions like delayed menstruation and reduced hormone levels contribute to this decreased fertility, similar to changes seen during menopause but due to inadequate caloric intake rather than aging.
Step-by-step explanation:
Low energy availability in girls can lead to a shift in energy allocation away from reproduction towards survival. This adaptation can reduce reproductive functions, leading to conditions such as infertility, which is the inability to conceive a child or carry a child to birth. This is often associated with hormonal imbalances within the endocrine system. One aspect of the endocrine system that can affect fertility in extremely thin females is the production of certain hormones, such as estrogen and progesterone, which are essential for regular menstruation and ovulation. Inadequate nutrition and the associated energy deficiencies can disrupt the hormonal balance, causing delayed menstruation and ovulation, and reducing fertility.
Such hormonal imbalances can be triggered by starvation or extreme dieting, leading to a decrease in gonadotropin sensitivity and a reduction in vital sex hormone levels. This is similar to what occurs as a woman approaches menopause, where there is a natural decline in ovarian function and hormone production, but in the case of low energy availability, the effect is not due to aging but due to insufficient caloric intake and the body prioritizing survival over reproductive processes.