Polycystic Ovary Syndrome (PCOS) is a common hormonal disorder affecting women of reproductive age. Its name, “polycystic,” often leads to questions about ovarian follicles. This article explores what ovarian follicles are, their significance in PCOS, and the specific number relevant for diagnosis.
What Are Ovarian Follicles?
Ovarian follicles are small, fluid-filled sacs located within the ovaries, each containing an immature egg. These structures are integral to the female reproductive system, playing a role in both egg development and hormone production. During a typical menstrual cycle, several follicles begin to grow, but usually, only one matures fully and releases its egg during ovulation.
Follicles are distinct from ovarian cysts, which are generally larger. Healthcare professionals can visualize and count these small follicles through ultrasound imaging, allowing for an assessment of ovarian health and function.
The Follicle Count for PCOS Diagnosis
The presence of numerous small follicles in the ovaries is a key indicator for a PCOS diagnosis. Current guidelines typically define polycystic ovarian morphology as having 20 or more antral follicles, each measuring between 2 and 9 millimeters in size, in at least one ovary. Alternatively, an ovarian volume greater than 10 milliliters can also meet this criterion.
This assessment is primarily conducted using a transvaginal ultrasound. The term “polycystic” in PCOS refers to these many small, underdeveloped follicles, rather than true cysts. This imaging finding is a significant component of established diagnostic criteria, such as the Rotterdam criteria.
While the follicle count is an important factor, it is rarely the sole basis for a PCOS diagnosis. Advances in ultrasound technology have led to higher resolution imaging, allowing for more precise follicle counts. This improved visualization has contributed to the updated threshold of 20 or more follicles, recognizing that older criteria might have overdiagnosed polycystic ovarian morphology.
Why Follicles Accumulate in PCOS
The accumulation of numerous small follicles in PCOS stems from underlying hormonal imbalances that disrupt normal follicular development. Elevated levels of androgens are a significant factor, interfering with the orderly maturation process of follicles.
Insulin resistance also plays a role, as it can lead to increased insulin levels, which in turn stimulate the ovaries to produce more androgens. This hormonal environment prevents the follicles from growing to their full size and releasing an egg. Consequently, these follicles become arrested at an immature stage, leading to their characteristic accumulation within the ovaries.
Other Diagnostic Signs of PCOS
A diagnosis of PCOS typically requires more than just the presence of numerous follicles. According to the widely accepted Rotterdam criteria, a woman must exhibit at least two out of three specific signs. These include the polycystic ovarian morphology discussed previously, alongside clinical or biochemical hyperandrogenism and ovulatory dysfunction.
Clinical hyperandrogenism refers to physical signs of elevated androgen levels, such as hirsutism (excessive hair growth), severe acne, and male-pattern hair loss. Biochemical hyperandrogenism is confirmed through blood tests showing elevated levels of androgens.
Ovulatory dysfunction is characterized by irregular, infrequent, or absent menstrual periods, indicating that ovulation is not occurring regularly or at all. This irregular ovulation is a common reason why women with PCOS experience difficulty conceiving. The combination of these criteria helps ensure an accurate diagnosis.