From the Guidelines
The hormonal ratio used to diagnose PCOS is the LH to FSH ratio, with a value greater than 2 often considered suggestive of PCOS. This ratio is a key diagnostic tool, as it reflects the hormonal imbalance characteristic of PCOS, where higher LH stimulates excessive androgen production by the ovaries 1. The LH to FSH ratio is often elevated in PCOS patients, exceeding 2, whereas in functional hypothalamic amenorrhea (FHA) patients, the ratio is typically less than 1, with recent data demonstrating a LH to FSH ratio <1 in about 82% of FHA patients 1.
Some key points to consider when using the LH to FSH ratio to diagnose PCOS include:
- The ratio alone is not sufficient for diagnosis, as not all women with PCOS will have an elevated LH:FSH ratio 1
- Current diagnostic criteria for PCOS typically require at least two of three features: irregular or absent menstrual cycles, clinical or biochemical signs of hyperandrogenism, and polycystic ovaries on ultrasound
- Blood tests should ideally be performed during the early follicular phase of the menstrual cycle (days 2-5) for accurate interpretation, though this may be challenging in women with irregular cycles
- A focused history and examination, pelvic ultrasound, and focused laboratory evaluation at the initial visit should be the standard approach to diagnose PCOS, with the LH to FSH ratio being a useful tool in this evaluation 1.
From the Research
Hormonal Ratio for Diagnosing PCOS
The hormonal ratio used to diagnose Polycystic Ovary Syndrome (PCOS) is:
- Luteinizing hormone (LH) to follicle-stimulating hormone (FSH) ratio, with a ratio of ≥ 1 considered significant for diagnosis 2 Some studies suggest that this ratio may not be the most effective criterion for diagnosis, as it has low sensitivity 3 Other hormonal markers, such as total testosterone, androstenedione, and LH, may be more effective in diagnosing PCOS, either alone or in combination 3
Key Findings
- The LH/FSH ratio was found to be significantly higher in women with PCOS compared to normal controls, but was only abnormal in 41-44% of PCOS cases 3
- The ratio of LH/FSH ≥ 1 was found to have a significant value in the diagnosis of PCOS, with areas under the ROC curve of 0.786 and 0.942 using the Rotterdam and Japan consensus criteria, respectively 2
- Total testosterone was found to be the most frequently abnormal biochemical marker for PCOS, with 70% of cases having elevated levels 3