SLOW DOWN: Take Your Time in Diagnosing PCOS in Adolescents

Polycystic ovarian syndrome (PCOS) is the most common ovulation disorder among adult reproductive-age women. This blog post will discuss the latest recommendations, which state that we should wait about 8 years after menarche to make this diagnosis in adolescents!

PCOS is defined by the Rotterdam Criteria as 2 of the following: irregular menstrual cycles (or absent cycles), hirsutism (clinically as acne or male-patterned hair growth or elevated androgens), and polycystic-appearing ovaries on ultrasound, also known as PCO morphology. In addition, other disorders that may look like PCOS need to be ruled out (thyroid disease, hyperprolactinemia, adrenal disorders). The two main areas where patients or providers have difficulty are how cycle lengths are determined and PCO morphology.

In gynecology and infertility, we see a number of women with irregular menstrual cycles. Irregular menstrual cycles are defined as cycles occurring more frequently than every 21 days or less frequently than every 35 days from the beginning of one cycle to the beginning of the next cycle (cycle day 1 to cycle day 1). Some patients get confused and count from the last day of bleeding to the first day of the next period, which artificially makes the cycle seem short. It is good to keep a menstrual calendar (a regular calendar where each day of bleeding is marked with an “X” and review it over a couple of months). It is easy to count the number of days from the beginning of one menstrual cycle to the beginning of the next when counting from the first “X” of one cycle to the first “X” of the next.

One manner of identifying polycystic ovaries is by the volume: If one or both ovaries has a volume of more than 10 cm3 then that meets the criteria for a polycystic ovary on ultrasound.

The other method of identification is counting and measuring follicles. Counting antral follicles, which are follicles that measure as less than 10 mm in diameter, in a polycystic-appearing ovary can be difficult. First, check to see if there are any cysts in the ovary (any large, space-occupying mass greater than 10 mm). If cysts larger than 10 mm are present, then the antral follicle counts and the ovarian volumes will be distorted. Typically, it is easiest to measure the antral follicles and ovarian volume in the early follicular phase, or cycle days 1–5 (where cycle day 1 is the first day of the menstrual period). In this early part of the menstrual cycle, there should not be a dominant follicle growing yet so the ovary commonly has only small antral follicles at this time in the cycle.

Originally, polycystic-appearing ovaries were described as having antral follicles lined up in the periphery of the ovary or a “pearl necklace” sign. In PCOS, the stroma of the ovary produces the androgens, and patients with PCOS tend to have a greater stromal area. However, the Rotterdam criteria did not use these descriptions in defining a polycystic-appearing ovary. Instead, the Rotterdam criteria state a volume or an antral follicle count when there are no cysts. The antral follicle count was initially described in the Rotterdam criteria as either ovary with more than 12 follicles (2–9 mm).

Unfortunately, with this number, a number of adolescents were being misdiagnosed with PCOS. Why would that be?

There are two reasons: one, when girls have menarche, the hypothalamic pituitary ovary axis is not mature and they will have irregular cycles—sometimes this irregularity lasts a couple of years. So, many adolescents were noted to have met the “irregular cycles” criterion. Second, adolescents have an excellent ovarian reserve. They should have a lot of antral follicles because they have a lot of eggs in the early part of their reproductive years. These ovaries are sometimes referred to as multi-follicular ovaries. This is a normal finding.  

Consequently, the international guideline, which has been adopted by the ESHRE (European Society of Human Reproduction and Embryology) and the ASRM (American Society of Reproductive Medicine) has concluded that the number of follicles needed to meet the PCO-appearing criteria should be 20 or more antral follicles (2–9 mm) in either ovary and others recommend 25 or more antral follicles.

They all accept that an ovary larger than 10 mL would meet the criterion. In addition, they have stated that we should NOT make the diagnosis of PCOS in adolescents within 8 years of their menarche because the reproductive axis is not mature early after menarche. Others have recommended NOT using the ultrasound criteria as an independent marker in diagnosing adolescents.

In other words, adolescents will need to have evidence of hirsutism and anovulation to meet the criteria of PCOS. The general consensus is that we do not want to inappropriately place a label of PCOS on these young women. PCOS has a lot of medical sequelae such as infertility, increased risk for insulin resistance, metabolic syndrome, diabetes, hypertension, and many others that could unnecessarily worry the young women.

Take home message: Be SLOW to diagnose PCOS in Adolescents! 


Teede HJ, Misso ML, Costello MF, Dokras A, Laven J, Moran L, Piltonen T, Norman RJ and International PCOS Network. Recommendations form the international evidence-based guideline for the assessment and management of polycystic ovary syndrome. Hum Reprod 2018; 1–17. Doi:10.1093/humrep/dey256

Al Wattar BH, Fisher M, Bevington L, Talaulikar V, Davies M, Conway G, Yasmin E. Clinical practice guidelines on the diagnosis and management of polycystic ovary syndrome: a systematic review and quality assessment study. J Clin Endocrinol Metab 2021; 106(8):2436–2446.

Dumesic DA, Oberfield SE, Stener-Victorin E, Marshall JC, Laven JS, Legro RS. Scientific statement on the diagnostic criteria, epidemiology and pathophysiology, and molecular genetic of polycystic ovary syndrome. Endocrine Reviews 2015; 36(5):487–525.

Elizabeth E. Puscheck, MD, MS, MBA, FACOG, FAIUM, is a board-certified Reproductive Endocrinologist practicing with InVia Ferility and a tenured Professor at Wayne State University School of Medicine.