If your period arrives every 45, 60 or even 90 days, it's worth understanding why.
And no, the answer isn't always polycystic ovaries.
Your menstrual cycle is regulated through a complex communication system involving your brain, pituitary gland and ovaries.
When this signalling becomes disrupted, ovulation may be delayed or absent, leading to longer or unpredictable menstrual cycles.
Understanding what's interrupting that communication is essential when investigating irregular periods.
How Is Your Menstrual Cycle Regulated?
The menstrual cycle is primarily controlled by the hypothalamic-pituitary-ovarian (HPO) axis.
The hypothalamus releases gonadotropin-releasing hormone (GnRH), which signals the pituitary gland to release follicle-stimulating hormone (FSH) and luteinising hormone (LH).
FSH supports ovarian follicle development, while the mid-cycle LH surge triggers ovulation.
After ovulation, the corpus luteum produces progesterone.
Disruptions at any point within this communication system can affect menstrual regularity.
1. PMOS (Formerly PCOS)
Polyendocrine metabolic ovarian syndrome (PMOS), previously called PCOS, is a common cause of irregular menstrual cycles.
It can involve ovulatory dysfunction, elevated androgen activity and metabolic features such as insulin resistance.
Not everyone with PMOS has insulin resistance, and not everyone has polycystic ovarian morphology.
Diagnosis requires appropriate assessment rather than relying on ultrasound findings alone.
Management depends on the individual's symptoms, metabolic health and reproductive goals.
2. Elevated Prolactin
Prolactin is best known for its role in breast milk production, but it also influences reproductive hormone signalling.
When prolactin is persistently elevated, it can suppress GnRH activity and interfere with ovulation.
This may lead to longer cycles, absent periods or difficulties conceiving.
Elevated prolactin can occur due to certain medications, thyroid dysfunction, physiological factors or pituitary conditions.
A mildly elevated result should be interpreted carefully and may require repeat testing.
3. Thyroid Dysfunction
Thyroid hormones influence metabolism and interact with reproductive hormone regulation.
Both hypothyroidism and hyperthyroidism can contribute to menstrual irregularities.
When thyroid function is impaired, changes in ovulatory function, menstrual bleeding and reproductive hormones may occur.
Symptoms such as fatigue, constipation, temperature intolerance or unexplained weight changes can provide additional clues.
Thyroid blood tests are particularly relevant when menstrual irregularities occur alongside symptoms suggestive of thyroid disease.
4. Hypothalamic Amenorrhoea
Functional hypothalamic amenorrhoea can occur when the brain reduces reproductive signalling in response to factors such as inadequate energy availability, psychological stress or excessive exercise.
Importantly, this doesn't only happen in people who are underweight.
Someone may be exercising frequently, eating what they perceive to be a healthy diet and still not consuming enough energy for their body's requirements.
When GnRH signalling is suppressed, LH and FSH activity can decrease, potentially reducing oestrogen production and disrupting ovulation.
Why Investigation Matters
Different causes of irregular periods require very different approaches.
Someone with insulin resistance may need different support from someone experiencing hypothalamic suppression due to inadequate energy intake.
This is why a thorough history and appropriately timed pathology testing matter.
Depending on symptoms, assessment may include thyroid function, prolactin, reproductive hormones, androgen levels and metabolic markers.
Pregnancy and other medical causes must also be considered.
The Takeaway
Your menstrual cycle provides useful information about your reproductive health.
If your cycles are consistently longer than 35 days, highly variable or absent, it's worth investigating rather than assuming it's simply your normal.
At Flora Whole Health, we focus on understanding the individual factors contributing to menstrual irregularities rather than applying the same protocol to every person.