PCOS and Menstrual Irregularities: Reading the Signals Your Body Sends

Irregular cycles are one of those things that can be easy to dismiss. "My cycle has always been unpredictable." "I've always been a bit different." "The doctor said it's normal for some women."

Sometimes that is true. But sometimes irregular cycles are the body's clearest signal that something specific is happening, and PCOS is one of the most common things happening.

What Counts as Irregular

Not every variation in cycle length is clinically significant. Cycles between 24 and 35 days, varying by a few days month to month, are within normal range.

What warrants attention:

• Cycles longer than 35 days consistently, not occasionally
• Amenorrhea: three or more consecutive months without menstruation
• Anovulation: cycles occurring without ovulation, which can produce bleeding that looks like a period but is not ovulation-based

Anovulation affects an estimated 85–90% of women with oligomenorrhea (infrequent periods). [FE: verify this figure] It is the mechanism behind PCOS-related infertility: no ovulation, no egg, no conception. PCOS accounts for 75–90% of anovulatory infertility cases, making it a leading cause of ovulatory infertility.

The Diagnostic Threshold

PCOS is diagnosed using the Rotterdam criteria, which requires two of three features:

1. Irregular or absent menstruation
2. Clinical or biochemical signs of elevated androgens (hirsutism, acne, or elevated testosterone on testing)
3. Polycystic ovaries on ultrasound

The diagnosis also requires ruling out other conditions that produce similar signs: thyroid disorders, hyperprolactinaemia, congenital adrenal hyperplasia. Blood tests and imaging are part of the process.

What this means practically: irregular cycles alone do not confirm PCOS. They are a reason to investigate, not a conclusion.

What Shows Up in the Body

Androgen excess (elevated testosterone or DHEAS) produces visible and measurable changes.

Hirsutism, excess hair growth in androgenic distribution (upper lip, chin, chest, inner thighs), affects up to 70% of women with PCOS. [FE: verify]

Acne occurs in 15–30% of PCOS cases, often appearing in the jawline and chin region. [FE: verify]

Androgenetic alopecia (hair thinning at the crown or temples) is less common but significant when present.

On bloodwork: elevated testosterone and reduced SHBG. Metabolic dysfunction (insulin resistance, elevated fasting glucose, abnormal lipids) occurs in 50–70% of women with PCOS, independent of body weight. [FE: verify]

That last point matters: you do not have to be overweight to have metabolic PCOS. Weight is a downstream effect of the metabolic dysfunction, not a prerequisite for it.

The Four Types, Again

As covered in a companion article, PCOS presents in at least four distinct forms. Understanding your type matters for management:

• Insulin-resistant (most common, ~70%): elevated insulin drives androgen production
• Post-pill: temporary rebound after stopping hormonal contraception
• Inflammatory: low-grade chronic inflammation as the driver
• Adrenal (~10%): elevated DHEAS from the adrenal glands, not the ovaries

This four-type framework is a popular educational model used by some practitioners to help identify likely contributing mechanisms; it is not a formal diagnostic category in endocrinology. Formal PCOS diagnosis follows the Rotterdam criteria (noted above).

A doctor who tests only total testosterone without also checking DHEAS and fasting insulin may miss the specific mechanism driving your symptoms.

What Your Cycle Chart Can Show

If you track your cycle with your partner using the Fertility Awareness Method, recording cervical mucus and basal body temperature daily, irregular cycles become legible rather than just frustrating.

A BBT chart from a PCOS cycle often shows: prolonged or unclear pre-ovulatory phase, delayed or absent temperature rise, multiple temperature peaks without confirmed ovulation, or an absent luteal phase. These are not failures, they are clinical information that shows how your body actually works. A chart showing three months of this pattern gives your doctor far more to work with than a verbal description, and it gives you both a way to plan the next step together.

Management: The Evidence Base

For insulin-resistant PCOS, science shows a clear path: your body can change through metabolic support.

• Diet: eliminate refined sugars and processed carbohydrates; prioritise omega-3-rich fish, leafy greens, whole grains, and foods that support stable blood glucose
• Movement: consistent moderate activity improves insulin sensitivity directly, two to three sessions per week of 30–45 minutes is where you start
• Tracking: regular cycle monitoring combined with FAM provides diagnostic insight and shows you the change

Anti-inflammatory nutrition (reducing processed food, increasing variety of vegetables, managing stress) is the lever for inflammatory-type PCOS. Each of these is something you can implement step by step.

One Next Step

If you have irregular cycles and have not had PCOS investigated: with your partner or on your own, ask your GP for a blood panel that includes testosterone, DHEAS, fasting insulin, and thyroid function. If PCOS is already diagnosed, ask which type and whether insulin has been tested, that conversation has real effects. The answer shapes your next step.

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Source: NatProFam.pl, Monika Dowejko. Adapted for FertilityFlow with Guide By Hand voice. Attribution required on publication. FE review required before publish. Key claims flagged for Fertility Expert verification: anovulation prevalence in oligomenorrhea (85–90%), PCOS proportion of anovulatory infertility (90–95%), hirsutism prevalence (70%), acne prevalence (15–30%), metabolic dysfunction prevalence (50–70%), insulin-resistant PCOS proportion (70%), adrenal PCOS proportion (10%).