Hormone Journal

Anovulation

Medically reviewed by Hormone Journal Editorial Team · Last reviewed 2026-05-22

Anovulation is the absence of ovulation during a menstrual cycle, accounting for roughly 30% of female infertility diagnoses and a leading cause of abnormal uterine bleeding.

What it is

Anovulation is the absence of ovulation during a menstrual cycle, accounting for roughly 30% of female infertility diagnoses and a leading cause of abnormal uterine bleeding across all reproductive-age groups. Also called ovulatory dysfunction (the term used in the FIGO AUB classification system), anovulation means the ovary does not release a mature egg during a given cycle — yet uterine bleeding can still occur, so having a "period" does not confirm that ovulation has taken place.

Anovulation is classified as either chronic — occurring consistently across many cycles, as in untreated polycystic ovary syndrome (PCOS) — or sporadic, occurring occasionally even in people with otherwise regular cycles. Research published in Human Reproduction (Hambridge et al., 2013) found that sporadic anovulatory cycles are associated with measurably lower estradiol, progesterone, and LH peak levels even in surrounding ovulatory cycles, suggesting a broader hormonal effect beyond the single missed ovulation. In Canada, anovulation is evaluated and managed within primary care, gynaecology, and reproductive endocrinology settings; LifeLabs and Dynacare both offer the serum progesterone and hormone-panel testing used to confirm the diagnosis.

Causes and mechanism

Normal ovulation depends on a precisely timed hormonal sequence: the hypothalamus releases gonadotropin-releasing hormone (GnRH), which prompts the pituitary to secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH). A sharp mid-cycle LH surge triggers egg release. Any disruption along this chain can cause anovulation.

CauseMechanismTypical population
PCOSElevated androgens and insulin resistance block follicle maturation and suppress the LH surgeMost common cause in reproductive-age people
Hypothalamic suppressionLow body weight, excessive exercise, or chronic stress reduce GnRH pulsingAthletes, those with restrictive eating patterns
HyperprolactinemiaElevated prolactin (pituitary adenoma or certain medications) suppresses GnRHAny age; medication review essential
Thyroid dysfunctionBoth hypothyroidism and hyperthyroidism alter sex hormone metabolismAny age; TSH is a standard first-line test
Premature ovarian insufficiency (POI)Follicle depletion before age 40 causes chronic anovulationPeople under 40 with elevated FSH
PerimenopauseDeclining ovarian reserve makes anovulatory cycles increasingly frequentTypically ages 40–51

Symptoms and diagnosis

Symptoms range from absent to pronounced. Common presentations include:

  • Cycles shorter than 21 days or longer than 35 days
  • Unpredictable, heavy, or prolonged uterine bleeding
  • Absence of mid-cycle signs such as mild pelvic pain or characteristic cervical mucus changes
  • Difficulty conceiving

Diagnosis typically proceeds in steps:

  1. Serum progesterone — measured approximately 7 days before the expected next period (mid-luteal phase). A level below 3 ng/mL strongly suggests anovulation.
  2. Hormone panel — FSH, LH, estradiol, prolactin, TSH, and androgens to identify the underlying cause.
  3. Pelvic ultrasound — assesses ovarian morphology (e.g., polycystic appearance) and endometrial thickness.
  4. Basal body temperature charting or urinary LH kits — accessible first-line tools for patients, though less precise than serum testing.

Because anovulatory bleeding can mimic a normal period, many people in Canada are unaware of the condition until they investigate irregular bleeding or attempt to conceive.

Treatment options

Treatment targets the underlying cause rather than anovulation as an isolated finding.

  • Lifestyle modification — weight normalization and reducing excessive exercise can restore ovulation in hypothalamic anovulation within weeks to months, without medication.
  • Ovulation induction — letrozole (an aromatase inhibitor) is now preferred over clomiphene citrate for PCOS-related anovulation, based on higher live-birth rates in randomized trials. FSH injections (gonadotropins) are used when oral agents fail or when the cause is hypothalamic-pituitary dysfunction.
  • Hormonal regulation — combined oral contraceptives or cyclic progestin therapy control bleeding and protect the endometrium from hyperplasia caused by prolonged unopposed estrogen exposure. These are used in people who are not trying to conceive.
  • Treating the root cause — thyroid hormone replacement for hypothyroidism, dopamine agonists (e.g., cabergoline) for hyperprolactinemia, or metformin for PCOS with significant insulin resistance.
  • Assisted reproduction — if ovulation induction does not achieve pregnancy, intrauterine insemination or IVF may be considered as a next step, typically through a fertility clinic or reproductive endocrinologist.

Canadian patients can access initial assessment and oral ovulation-induction prescriptions through primary care or virtual platforms (Felix, Maple, Cleo, Phoenix, and others); referral to a reproductive endocrinologist is standard when first-line treatments are unsuccessful.

When to see a clinician in Canada

Seek evaluation if:

  • Cycles are consistently shorter than 21 days or longer than 35 days
  • Bleeding lasts more than 7 days or is unpredictable in timing and heaviness
  • You have been trying to conceive for 12 months without success — or 6 months if you are over 35
  • You have had no period for 3 or more consecutive months and are not pregnant
  • You have known risk factors such as PCOS, a history of disordered eating, or significant recent weight change

Chronic anovulation left untreated raises the risk of endometrial hyperplasia over time due to prolonged unopposed estrogen exposure. The Society of Obstetricians and Gynaecologists of Canada (SOGC) includes anovulatory bleeding in its abnormal uterine bleeding guidelines, and most provincial health plans cover the diagnostic bloodwork and ultrasound required for initial workup.

Limitations and open questions

Research is still emerging on the long-term cardiovascular and metabolic consequences of chronic anovulation independent of PCOS. The optimal duration of letrozole cycles before escalating to gonadotropins is not firmly established across all anovulation subtypes. Health Canada has not issued specific guidance on anovulation management separate from its broader reproductive health frameworks, meaning Canadian clinicians largely follow Endocrine Society and SOGC guidelines adapted from international evidence. The significance of sporadic anovulation in otherwise fertile people — and whether it warrants treatment — remains an area of active investigation. Patients with premature ovarian insufficiency face a distinct prognosis that standard ovulation-induction protocols do not adequately address, and evidence for fertility-preserving interventions in this group remains limited.

FAQs

Can you have a period without ovulating?

Yes. Uterine bleeding can occur without ovulation when the endometrial lining sheds after a period of estrogen stimulation — this is called anovulatory bleeding. Because no egg is released, no corpus luteum forms and no progesterone is produced, so the cycle lacks a normal luteal phase. The resulting bleeding is often irregular or heavier than a typical period, and a serum progesterone below 3 ng/mL in the mid-luteal phase can confirm that ovulation did not occur.

How common is anovulation?

Sporadic anovulatory cycles occur in an estimated 20–35% of menstrual cycles even in otherwise fertile people, particularly at the extremes of reproductive age — in the early years after the first period and during perimenopause. Chronic anovulation accounts for approximately 30% of all female infertility diagnoses, with PCOS being the single most common underlying cause.

What is the difference between anovulation and amenorrhea?

Amenorrhea means no uterine bleeding for 3 or more consecutive months, while anovulation means no egg is released — and bleeding may still occur with anovulation. The two conditions often overlap: chronic anovulation can eventually lead to amenorrhea if estrogen levels fall low enough to stop stimulating the uterine lining. Both require clinical evaluation to identify the underlying cause, as the treatments differ depending on whether the problem originates in the ovary, pituitary, or hypothalamus.

Can anovulation be treated so I can get pregnant?

In most cases, yes. Ovulation induction with letrozole or clomiphene citrate is effective for PCOS-related anovulation in the majority of patients, with letrozole now preferred based on higher live-birth rates in randomized trials. Hypothalamic anovulation caused by low body weight or excessive exercise often resolves with weight restoration and activity modification alone, without medication. Premature ovarian insufficiency has a lower response to standard ovulation-induction treatments, and those patients are typically referred to a reproductive endocrinologist to discuss assisted reproduction options.

Is diagnostic testing for anovulation covered in Canada?

In most provinces, the bloodwork used to investigate anovulation — including serum progesterone, FSH, LH, TSH, prolactin, and estradiol — is covered under provincial health insurance when ordered by a physician or nurse practitioner for a medically indicated reason such as irregular cycles or infertility. Pelvic ultrasound is similarly covered in most provinces when clinically indicated. Patients using virtual care platforms should confirm whether their province covers lab requisitions issued through telemedicine, as coverage rules vary.

Sources

All glossary termsUpdated 2026-05-22