The Rotterdam criteria are the widely accepted diagnostic tool for Polycystic Ovary Syndrome (PCOS). To be diagnosed with PCOS, a woman must meet at least two of the following three criteria:
- Blood results or signs of high male hormones (androgens): This includes symptoms like acne or increased body hair.
- Absent or infrequent periods: Irregular menstrual cycles, cycles >45 days apart or less than 8 periods per year
- Polycystic ovaries on ultrasound: The presence of >20 follicles per ovary (this is a common finding in younger people and does not automatically mean someone has PCOS)
While the Rotterdam criteria are useful, they have faced criticism for potentially leading to over-diagnosis. For instance, someone with missed periods and a few pimples might be classified as having PCOS.
Lean PCOS is often confused with functional hypothalamic amenorrhea (FHA), which is associated with Relative Energy Deficiency in Sport (RED-S) or anorexia. Although weight loss is not recommended for either condition, their treatments differ significantly. For example, progesterone protection is crucial in PCOS, whereas patients with FHA are at risk of osteoporosis.
Accurate diagnosis is essential because both conditions can present with elevated Anti-Müllerian Hormone (AMH), polycystic ovaries on ultrasound, and amenorrhoea. During the recovery of the pituitary-ovarian axis in FHA, elevated androgens can also be observed. This overlap highlights the complexity of diagnosing these conditions based on blood tests alone. Additionally, some individuals with lean PCOS may develop FHA and revert to PCOS upon recovery.
Here are some ways to differentiate PCOS from FHA:
- Oestrogen levels: Low in FHA but generally normal in PCOS.
- LH and FSH levels: LH usually lower than FSH in FHA, whereas PCOS usually has a high LH vs FSH
- Ultrasound findings: A thickened endometrial lining suggests PCOS, while a thin endometrium supports FHA.
- Progesterone challenge test: No withdrawal bleed suggests FHA.
- Insulin resistance: May support a diagnosis of PCOS.
- Thyroid hormones: Low thyroid hormones with low TSH (non-thyroidal illness) and other markers of low energy availability such as growth hormone resistance support FHA/RED-S
- Androgen levels: Mildly elevated androgens without clinical signs may support FHA.
In addition to a thorough history, including lifestyle and family history, diagnosing PCOS also involves ruling out other conditions such as hypothyroidism, congenital adrenal hyperplasia, or elevated prolactin levels.
Take-home message: PCOS is a diagnosis of exclusion, and athletes should be thoroughly screened for FHA, especially since recovery from FHA may temporarily mimic mild PCOS. 💛