The loss of a menstrual period, known as amenorrhea, in highly active females is a serious signal of internal distress. This condition, often termed athletic amenorrhea, is the body’s way of shutting down a non-survival function to conserve resources. It is not an inevitable side effect of intense training, but rather a sign of an underlying energy imbalance that protects the body from perceived famine and can have profound effects on long-term health.
The Primary Cause Low Energy Availability
The root cause of menstrual dysfunction in athletes is a state called Low Energy Availability (LEA), which is a deficit in the net energy remaining for basic bodily functions after exercise. Energy Availability is a calculation determined by subtracting the energy expended during exercise from the total energy consumed through diet. The resulting figure is the energy available to fuel all other necessary physiological processes, such as metabolism, immunity, and reproduction.
This condition is not strictly tied to having a low body mass index or a visibly low body fat percentage. Athletes can maintain a normal weight while experiencing LEA if their caloric intake fails to keep pace with high training volume. When this imbalance becomes chronic, the body shifts into a survival mode, prioritizing energy for movement and basic survival over reproduction.
The comprehensive term for this health concern is Relative Energy Deficiency in Sport (RED-S), which recognizes that LEA affects multiple body systems in both male and female athletes. In females, menstrual dysfunction is the most recognizable symptom of this energy crisis, but the underlying deficit affects far more than the reproductive system. The threshold for LEA is defined as less than 30 kilocalories per kilogram of fat-free mass per day, a level too low to support optimal health.
Suppressing the Reproductive Hormonal Cascade
The body translates the signal of low energy availability into the cessation of the menstrual cycle through the neuroendocrine system, specifically the Hypothalamic-Pituitary-Ovarian (HPO) axis. Insufficient energy intake suppresses the release of Gonadotropin-Releasing Hormone (GnRH) from the hypothalamus. This suppression is a direct adaptive response, with the brain perceiving the environment as unsuitable for pregnancy.
GnRH is normally released in a pulsatile fashion, which stimulates the pituitary gland to produce Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH). When GnRH pulses slow down or become less frequent due to LEA, the pituitary gland cannot release adequate levels of LH and FSH. These gonadotropins are required to stimulate the ovaries to produce estrogen and progesterone, which drive the menstrual cycle and ovulation.
The resulting low levels of estrogen cause the condition known as functional hypothalamic amenorrhea. Without the necessary hormonal stimulation, the uterine lining fails to build up, and the athlete stops menstruating. This shutdown conserves metabolic energy by halting the reproductive process.
Long Term Health Consequences Beyond Menstruation
The loss of the menstrual period is a symptom of low estrogen, and this chronic state of hypoestrogenism leads to long-term health issues. Estrogen regulates bone remodeling by promoting the activity of bone-building cells. When estrogen levels are suppressed, bone resorption outpaces bone formation, leading to a decrease in bone mineral density (BMD). This compromised bone health increases the risk of stress fractures, often the first injury an athlete with LEA experiences.
If the condition persists, the athlete may develop osteopenia or even osteoporosis, permanently compromising skeletal strength. Since peak bone mass is primarily accrued during the adolescent and young adult years, this period of suppressed estrogen can result in a permanent bone deficit that may never be fully recovered.
Beyond skeletal issues, chronic low estrogen can also negatively impact the cardiovascular system. Studies suggest that amenorrheic athletes show impaired endothelial function and adverse changes in lipid profiles, including elevated levels of total cholesterol, LDL, and VLDL. These alterations in vascular health suggest an increased risk for premature cardiovascular disease, despite the athlete’s high level of physical fitness.
Diagnosis and Recovery
Diagnosing functional hypothalamic amenorrhea is often a diagnosis of exclusion, requiring other medical causes for the loss of a period to be ruled out through blood work assessing thyroid function, prolactin levels, and other reproductive hormones. If the condition is prolonged, a bone density scan, such as a DEXA scan, may be used to assess the degree of bone loss and determine the severity of the health risk.
The treatment is to address the underlying energy deficit. This involves behavioral and nutritional counseling to either increase caloric intake, decrease training load, or both, until energy availability is restored. The goal is to reach a sufficient energy balance that signals to the hypothalamus that the body is safe and nourished enough to resume reproductive function.
Prescribing hormonal birth control is not a treatment for this condition, as it does not correct the energy imbalance. While oral contraceptives can induce a withdrawal bleed, masking the underlying problem of LEA, they may not restore bone mineral density effectively. True recovery is marked by the spontaneous return of the natural menstrual cycle, confirming that the body’s energy status is fully restored.