Each month, ovaries normally grow cyst-like structures called follicles. Follicles produce the hormones estrogen and progesterone and release an egg when ovulation occurs.
“If a normal monthly follicle keeps growing, it’s known as a functional cyst. There are two types of functional cysts:
- Follicular cyst. Around the midpoint of your menstrual cycle, an egg bursts out of its follicle and travels down the fallopian tube. A follicular cyst begins when the follicle doesn’t rupture or release its egg, but continues to grow.
- Corpus luteum cyst. When a follicle releases its egg, it begins producing estrogen and progesterone for conception. This follicle is now called the corpus luteum. Sometimes, fluid accumulates inside the follicle, causing the corpus luteum to grow into a cyst.” Source: Mayoclinic.org.