What is the likely cause of amenorrhea in a 14-year-old gymnast with increasing training intensity?

The most likely cause of amenorrhea in a 14-year-old gymnast experiencing an increase in training intensity is functional hypothalamic gonadotropin-releasing hormone (GnRH) deficiency. This condition often occurs in young athletes, particularly those engaged in intense physical training, such as gymnastics, which can lead to significant changes in hormonal balance and energy availability.

Increased training intensity can cause stress on the body, leading to decreased body fat and energy levels. This state prompts the hypothalamus to reduce the secretion of GnRH, disrupting the normal signaling to the pituitary gland and thereby impairing the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). This disruption can result in anovulation and ultimately amenorrhea, commonly referred to as exercise-associated amenorrhea.

This condition reflects a state of energy deficiency rather than a structural problem with the reproductive system, which is significant in understanding why it is more relevant in the context of an athlete's training regimen. Other conditions like Cushing syndrome or polycystic ovary syndrome may involve hormonal imbalances but are not as directly linked to the physical exertion and energy deficits seen in young athletes. Growth hormone deficiency is also less common and involves