What causes ovarian cysts?

Causes of Ovarian Cysts

Most ovarian cysts are functional in nature, arising from normal physiological processes of the menstrual cycle, and typically resolve spontaneously without treatment. 1, 2, 3

Physiological (Functional) Cysts

The most common cause of ovarian cysts in premenopausal women is normal ovarian function:

• Follicular cysts develop when a dominant follicle fails to rupture during ovulation, continuing to grow beyond its normal size 2, 3
• Corpus luteum cysts form when the corpus luteum fails to involute after ovulation and instead fills with fluid or blood 2
• These functional cysts are directly related to the hormonal milieu and developmental stage of the patient 3
• Simple cysts ≤5 cm are considered physiologic and require no management in premenopausal women 4, 5
• Most functional cysts resolve spontaneously within 2-3 cycles without intervention 1, 2

Hemorrhagic Cysts

• Occur when bleeding develops within a functional cyst 4
• Present with characteristic "cobweb" appearance or retractile clot on ultrasound with peripheral vascularity 4
• Represent a complication of normal functional cyst development 2

Endometriomas

• Result from endometrial tissue implanting on the ovary, typically in women with endometriosis 4
• Display low-level internal echogenicity on ultrasound with echogenic mural foci or non-vascular solid components 4
• These are pathological rather than physiological cysts 1

Dermoid Cysts (Mature Cystic Teratomas)

• Arise from germ cells and represent the most common ovarian tumor, accounting for 20% of all ovarian tumors 6
• Contain mature tissues including hair, teeth, and cartilage with characteristic appearance on imaging 6
• Usually benign but account for >75% of ovarian tumors in younger patients 6

Polycystic Ovary Syndrome (PCOS)

• Characterized by chronic anovulation leading to multiple small follicular cysts 6
• Associated with hyperandrogenism, insulin resistance, and metabolic dysfunction 6
• Requires exclusion of other causes of androgen excess including Cushing's syndrome, androgen-secreting tumors, and congenital adrenal hyperplasia 6

Germ Cell Tumors

• Account for 5% of ovarian tumors but represent 80% of preadolescent malignant ovarian tumors 6
• Include dysgerminomas, endodermal sinus tumors, and immature teratomas 6
• Occur mainly in young women and children 6

Sex Cord-Stromal Tumors

• Represent 3-5% of ovarian malignancies with yearly incidence of 2.1/1,000 women 6
• Include granulosa cell tumors (most common type, occurring in middle-aged and postmenopausal women) and Sertoli-Leydig cell tumors (occurring in adolescents) 6
• Arise from cells specific to the ovary including granulosa cells, theca cells, and stromal fibroblasts 6

Ovulation Induction

• Cysts can develop iatrogenically following ovulation induction therapy 1
• These treatment-related cysts behave similarly to spontaneous functional cysts and typically resolve without intervention 1

Age-Related Considerations

Critical distinction: The etiology varies dramatically with developmental stage 3:

• Neonates/infants: Cysts result from maternal hormonal stimulation 3
• Prepubertal children: Most cysts are functional but malignancy risk is higher proportionally 3, 7
• Reproductive age: Predominantly functional cysts from normal ovarian activity 2
• Postmenopausal: Higher proportion of pathological cysts; risk of malignancy increases from 1:1,000 at reproductive age to 3:1,000 at age 50 2

Common Pitfall to Avoid

Do not assume all persistent cysts are functional—cysts that persist beyond 2-3 cycles tend to be pathological (endometriomas, dermoid cysts, or neoplasms) rather than physiological and warrant further evaluation 1, 2.