follicular phase
First phase of the menstrual cycle characterized by follicle development and estrogen rise.
Full Definition
The follicular phase is the first half of the menstrual cycle, beginning with menstruation and ending with ovulation. During this phase, rising levels of follicle-stimulating hormone (FSH) stimulate the development of ovarian follicles, while the dominant follicle produces increasing amounts of estradiol. This estrogen rise leads to endometrial proliferation in preparation for potential implantation. In natural cycles, the follicular phase typically lasts 10-16 days, with ovulation triggered by a surge in luteinizing hormone. In assisted reproductive technology, the follicular phase is often manipulated through controlled ovarian hyperstimulation to produce multiple mature follicles simultaneously. Understanding follicular phase physiology is essential for timing fertility treatments and monitoring ovarian response.
Usage
Usage note: Distinguish from proliferative phase, which refers specifically to endometrial changes.
In Context
- "Monitoring during the follicular phase showed appropriate estradiol rise with follicle development." — Treatment cycle notes
- "The follicular phase was prolonged due to slow follicular recruitment." — Medical record