Menstrual irregularities in adolescents: When to investigate

Menstrual irregularities are common during adolescence, but determining when an abnormal cycle warrants further evaluation requires pediatricians to consider the time since menarche, signs of hyperandrogenism, and potential underlying endocrine or nutritional conditions, according to Nikta Forghani, MD.

Forghani, a pediatric endocrinologist at Rady Children's Health in Orange County, discussed menstrual cycle abnormalities, diagnostic considerations for polycystic ovary syndrome (PCOS), relative energy deficiency in athletes, and fertility preservation at the American Academy of Pediatrics (AAP) 2026 National Conference & Exhibition.

She emphasized that although some menstrual variability is expected during puberty, persistent irregularities should not automatically be dismissed as normal adolescent development.

When should irregular menstrual cycles prompt evaluation?

Forghani explained that expected menstrual cycle intervals change during the first several years after menarche, making the timing of menstrual abnormalities an important consideration.

During the first year after menarche, substantial cycle variability is expected. However, after that initial year, menstrual intervals exceeding 90 days warrant attention.

Between 1 and 3 years after menarche, cycles generally should occur every 21 to 45 days. By 3 years after menarche, the expected interval narrows to approximately 21 to 35 days.

Persistent cycles outside these ranges may indicate an underlying endocrine condition and should prompt further assessment.

"So, does a pediatrician need to work up every single patient who fits those criteria? That one time that you see you in clinic, perhaps not," Forghani said. "But if you see a child who is reporting those types of cycles, that would definitely be something to follow up on."

She emphasized that persistent abnormalities, rather than an isolated irregular cycle, are particularly important when deciding whether additional evaluation is necessary.

For pediatricians, documenting menstrual history and monitoring cycle patterns over time can help distinguish expected pubertal variability from abnormalities requiring investigation.

How is PCOS diagnosed in adolescents?

Forghani discussed the challenges of diagnosing PCOS during adolescence, when irregular menstrual cycles and acne may overlap with typical pubertal development.

She highlighted international guidance that distinguishes adolescent diagnostic criteria from those used in adults.

Two primary findings are required for an adolescent PCOS diagnosis: menstrual irregularity and clinical or biochemical evidence of hyperandrogenism.

Clinical hyperandrogenism may manifest as acne or hirsutism, while biochemical evidence includes elevated testosterone or free testosterone levels.

However, Forghani cautioned that some degree of acne is common during puberty, making it important to identify presentations that are unusually severe or do not respond to conventional treatment.

"So again, kind of having a keen eye for someone who's maybe not responding to traditional treatment, or someone who's developed severe acne out of the norm, the what you usually see," she said.

Another challenge involves adolescents who demonstrate concerning features but have not yet met the full diagnostic criteria for PCOS.

Forghani emphasized that these patients should not be overlooked simply because an official diagnosis cannot yet be established.

Pediatricians should continue monitoring menstrual patterns and signs of hyperandrogenism, particularly when symptoms persist or become more pronounced.

What menstrual changes may indicate relative energy deficiency?

Menstrual abnormalities can also provide important clues to relative energy deficiency in sport (RED-S), a condition that may affect adolescents whose energy intake is insufficient to support both physical activity and normal physiologic function.

Forghani emphasized that RED-S is not limited to athletes traditionally associated with intensive training, such as gymnasts or dancers.

Instead, menstrual irregularities may occur in adolescents participating in a wide range of sports and physical activities.

"It could be really any athlete or any girl who appears to be exercising with a certain level of frequency, and now is starting to have some irregularity in her period," Forghani said.

Changes in menstrual regularity between athletic seasons and periods of reduced training may provide additional clues.

She also highlighted the relationship between relative energy deficiency and bone health.

Adolescent athletes experiencing recurrent stress fractures or other stress injuries may have underlying bone health concerns associated with inadequate energy availability.

"So again, if you see an athlete, again may not fit that exact stereotype, but has had multiple stress injuries, may be a clue that that person's bone health is not what you would expect for their age," Forghani said.

For pediatricians, asking about menstrual patterns alongside athletic participation and injury history may help identify patients who require further evaluation.

When should fertility preservation enter the conversation?

Forghani also addressed the evolving role of fertility counseling and preservation in adolescents with reproductive endocrine conditions.

She noted that fertility preservation is an area of growing clinical and research interest, particularly for patients at risk of premature ovarian insufficiency (POI).

One example involves adolescents with Turner syndrome mosaicism who may develop ovarian insufficiency over time rather than presenting with it at birth.

For these patients, Forghani emphasized the importance of discussing reproductive options before ovarian function declines.

"I think we should for sure be having pointed conversations with those families before the onset of POI of what are the reproduction of reproductive options, you know, for those patients," she said.

For adolescents with PCOS or those considered at risk for the condition, Forghani noted that research continues to explore how management during adolescence may influence future reproductive health.

She highlighted lifestyle management as an important consideration but distinguished these conversations from formal fertility preservation counseling, which may not be necessary for all adolescents with menstrual irregularities.

Ultimately, Forghani's recommendations underscore the importance of evaluating menstrual abnormalities within the broader context of adolescent development, endocrine health, athletic participation, and future reproductive concerns.

For pediatricians, recognizing persistent cycle abnormalities and associated clinical findings can support earlier identification of patients who may benefit from additional evaluation or specialty care.

Reference

Forghani N. Evaluation and Management of Menstrual Disorders in Teens. Presented at: American Academy of Pediatrics 2026 National Conference & Exhibition; October 4, 2026; San Diego, CA.