Ovarian Cysts: Types, Causes & When to Take Action

Being told you have an ovarian cyst can feel alarming — particularly the first time. But for the majority of women, ovarian cysts are a normal part of the menstrual cycle and resolve on their own within a few cycles. The key is understanding what type of cyst you're dealing with, what it's signalling about your hormonal health, and when it requires medical attention versus watchful waiting.

This article cuts through the confusion — particularly around the overlapping terminology of "cysts" in PMOS (formerly PCOS), endometriomas, and functional cysts — and gives you a clear framework for understanding your situation.

What Ovarian Cysts Are

An ovarian cyst is a fluid-filled sac that develops on or within an ovary. They are extremely common — it's estimated that most women will develop at least one ovarian cyst during their reproductive years, and many will never be aware of it. The vast majority are benign (non-cancerous), and many resolve spontaneously without treatment.

The word "cyst" sounds alarming, but the important distinctions are type, size, and behaviour over time. A simple, fluid-filled functional cyst of 3 cm that resolves in the next cycle is categorically different from a complex, solid-component cyst or a large endometrioma.

Functional Cysts: Normal vs. Prolonged

Functional cysts arise as part of the normal menstrual cycle and are by far the most common type of ovarian cyst. There are two main types:

Follicular cysts

Each month, a follicle in the ovary grows to house a developing egg. At ovulation, the follicle ruptures to release the egg. If the follicle doesn't rupture — as happens in anovulatory cycles — the follicle continues to grow and becomes a follicular cyst. These are typically simple (fluid-only), often painless, and usually resolve within 1–3 cycles as the cyst gradually absorbs.

Corpus luteum cysts

After ovulation, the empty follicle transforms into the corpus luteum, which produces progesterone. If the corpus luteum doesn't dissolve properly, it can fill with fluid and become a corpus luteum cyst. These are sometimes larger than follicular cysts and can cause a dull ache or sharp pain if they bleed into themselves or rupture. They also typically resolve without treatment.

Recurring functional cysts — particularly recurring follicular cysts — are a signal that ovulation is being disrupted regularly. This is worth investigating rather than simply monitoring.

Pathological Cysts

Pathological cysts are not part of the normal ovulatory process and require more careful evaluation:

• •Endometriomas ("chocolate cysts") — formed when endometriosis tissue invades the ovary and bleeds internally, creating a cyst filled with dark, old blood. They can range from 1–10+ cm and are associated with endometriosis symptoms (pelvic pain, painful periods, painful sex). They require specialist management and may affect ovarian reserve and fertility.
• •Dermoid cysts (mature teratomas) — contain a variety of tissue types including hair, skin, and sometimes teeth or bone (because they develop from germ cells). They grow slowly, are almost always benign, but can become quite large and require surgical removal if symptomatic or large.
• •Cystadenomas — develop from ovarian tissue; serous cystadenomas are filled with watery fluid, mucinous cystadenomas with thick mucus. They can become very large. The vast majority are benign but they require monitoring and often removal.
• •Ovarian cancer — rare, but complex cysts with solid components, thick walls, or multiple septa in postmenopausal women warrant prompt evaluation by a specialist.

The PMOS (formerly PCOS) Confusion

One of the most common sources of confusion in ovarian cyst discussions is the term "polycystic ovaries" in PMOS (formerly PCOS). The "cysts" in PMOS (formerly PCOS) are not truly cysts in the pathological sense — they are antral follicles: small, immature follicles (2–9 mm) that have failed to complete the maturation process required for ovulation. They accumulate because the hormonal environment in PMOS (formerly PCOS) prevents a single dominant follicle from maturing to the point of ovulation.

These antral follicles are typically harmless — they don't rupture, cause acute pain, or develop into the type of cysts that require surgical management. They are a marker of disrupted ovulation, not a structural pathology in themselves. Understanding this distinction prevents unnecessary alarm when an ultrasound shows "polycystic-appearing ovaries."

Importantly, polycystic-appearing ovaries on ultrasound are found in approximately 20% of women who do not meet the diagnostic criteria for PMOS (formerly PCOS) — so the ultrasound finding alone is not diagnostic.

Symptoms to Know

Many ovarian cysts are discovered incidentally on ultrasound without ever causing symptoms. When symptoms do occur, they include:

• •Pelvic pain — dull, aching discomfort on one side; may be constant or intermittent
• •Bloating and fullness — particularly with larger cysts creating pressure in the pelvis
• •Painful periods — particularly with endometriomas
• •Irregular periods — cysts that disrupt ovulatory function can affect cycle regularity
• •Pain during sex — particularly with larger cysts or endometriomas
• •Urinary frequency or difficulty emptying the bladder — with cysts creating pressure on the bladder

Why Cysts Keep Coming Back

Recurrent functional cysts — where new cysts form cycle after cycle — signal that ovulation is being repeatedly disrupted. The most common underlying drivers include:

• •Estrogen dominance: excess estrogen drives follicular development but impairs the LH surge needed for ovulation, leading to follicular cysts
• •Insulin resistance (PMOS (formerly PCOS)): high insulin interferes with follicle maturation and the LH surge, preventing ovulation and contributing to the accumulation of antral follicles
• •Thyroid dysfunction: hypothyroidism disrupts the normal hormonal cascade of the cycle and can impair ovulation
• •HPA axis dysregulation: chronic stress suppresses GnRH and LH, disrupting the ovulatory trigger

Addressing these underlying drivers — rather than just monitoring cysts or suppressing them with hormonal contraceptives — is the root-cause approach to recurrent cyst formation.

When to Seek Medical Attention

Seek prompt medical attention — same day or emergency — if you experience:

• •Sudden, severe one-sided pelvic pain — this could indicate cyst rupture or ovarian torsion (twisting), both of which require prompt evaluation. Ovarian torsion is a surgical emergency.
• •Severe pain accompanied by fever and vomiting — may indicate infection or torsion
• •Signs of significant internal bleeding — dizziness, rapid heartbeat, feeling faint after sudden pelvic pain

Seek non-urgent medical review for: a known cyst larger than 5 cm that has not resolved after 2–3 cycles; a cyst with complex features on ultrasound (solid components, thick walls, multiple septa); a cyst in a postmenopausal woman; or symptoms that are significantly affecting your quality of life.

Natural Approaches to Support Ovarian Health

For women with recurrent functional cysts, addressing the hormonal environment that's disrupting ovulation is the most impactful approach:

• •Support ovulation: vitex agnus-castus, myo-inositol (particularly for PMOS (formerly PCOS)-related cysts), adequate zinc and B vitamins, and stress reduction all support healthy ovulatory function
• •Address estrogen dominance: liver support (cruciferous vegetables, DIM), gut health (estrobolome support), and reducing xenoestrogen exposure reduce the estrogen excess that disrupts follicular maturation
• •Manage blood sugar: for insulin-driven cyst formation (PMOS (formerly PCOS) pattern), the most important intervention is stabilising blood sugar through diet and myo-inositol supplementation
• •Castor oil packs: applied to the lower abdomen, traditional naturopathic therapy believed to support lymphatic circulation and reduce inflammation in the pelvic organs. Many women find them helpful for discomfort from functional cysts.

Medical Treatment Options

For functional cysts that are not resolving, or for pathological cysts, medical options include:

• •Watchful waiting: appropriate for simple functional cysts under 5 cm — repeat ultrasound in 6–8 weeks to confirm resolution
• •Hormonal contraception: can suppress ovarian activity and reduce the formation of new functional cysts; does not shrink existing cysts and is not appropriate for all women or all cyst types
• •Laparoscopic cystectomy: surgical removal of the cyst, ideally with preservation of the ovary; appropriate for cysts that are large, complex, symptomatic, or not resolving
• •For endometriomas: specialist surgical excision by an endometriosis surgeon is preferred; drainage alone has a very high recurrence rate