From the Guidelines
An elevated LH to FSH ratio is a significant diagnostic marker for Polycystic Ovary Syndrome (PCOS), typically considered relevant when the ratio exceeds 2:1, as indicated by recent studies 1. This hormonal imbalance reflects the underlying pathophysiology of PCOS, where excessive LH stimulates ovarian theca cells to produce androgens while relatively insufficient FSH fails to properly develop follicles, contributing to anovulation and cyst formation. While this ratio is helpful in diagnosis, it should not be used in isolation but rather as part of the Rotterdam criteria, which requires two of three findings: oligo/anovulation, hyperandrogenism (clinical or biochemical), and polycystic ovaries on ultrasound. The elevated ratio is most useful when measured during the early follicular phase (days 2-4 of the menstrual cycle) for accuracy, as suggested by studies on PCOS diagnosis and management 1. Some key points to consider in the diagnosis and management of PCOS include:
- The use of the LH to FSH ratio in distinguishing PCOS from other conditions such as functional hypothalamic amenorrhea (FHA), where the ratio is often lower than in PCOS 1.
- The importance of considering clinical symptoms and other hormonal parameters in addition to the LH:FSH ratio in ongoing PCOS management 1.
- Management strategies targeting the hormonal imbalance of PCOS, including the use of combined oral contraceptives and metformin to improve insulin sensitivity and reduce androgen production 1.
- The preference for letrozole over clomiphene citrate for ovulation induction in women with PCOS seeking pregnancy, as indicated by recent guidelines and studies 1. Overall, the diagnosis and management of PCOS require a comprehensive approach that considers multiple factors beyond just the LH:FSH ratio, including clinical presentation, hormonal parameters, and individual patient needs.
From the Research
Significance of Elevated LH to FSH Ratio in PCOS
- The elevated Luteinizing Hormone (LH) to Follicle-Stimulating Hormone (FSH) ratio is a common feature in Polycystic Ovary Syndrome (PCOS) patients, with 94% of anovulatory PCOS patients having an elevated LH to FSH ratio 2.
- This elevated ratio is associated with defects in gonadotropin secretion, including an increased frequency and amplitude of LH pulsations 2.
- The LH to FSH ratio can be used as a diagnostic tool for PCOS, with a ratio of >2.11 or >1.72 at 30 or 60 minutes after GnRH stimulation having 78.3% and 87.5% sensitivity and 81.7% and 81.3% specificity for the diagnosis of PCOS, respectively 3.
Relationship Between LH to FSH Ratio and PCOS Symptoms
- The elevated LH to FSH ratio is associated with hyperandrogenism, insulin resistance, and anovulation in PCOS patients 2, 3.
- The ratio is also correlated with body mass index (BMI) and body fatness, with a negative correlation between pool LH and BMI 2.
- However, the relationship between LH to FSH ratio and PCOS symptoms can vary depending on the phase of the menstrual cycle and the individual patient's characteristics 4.
Impact of Elevated LH to FSH Ratio on Treatment Outcomes
- Elevated baseline LH/FSH ratio is associated with poor ovulatory response but better clinical pregnancy and live birth in Chinese women with PCOS after ovulation induction 5.
- The ratio does not have a significant impact on pregnancy rates in PCOS patients undergoing in vitro fertilization (IVF) with GnRH-agonist/antagonist protocols or in vitro maturation (IVM) treatments 6.
- However, women with elevated LH/FSH ratio may have a higher likelihood of achieving clinical pregnancy and live birth despite poor ovulatory response 5.