LH/FSH ratio - What does it mean?

The LH/FSH ratio represents the ratio between luteinizing hormone (LH) and follicle stimulating hormone (FSH) and serves as a diagnostic criterion. These hormones are usually measured in the blood when ovarian dysfunction (ovarian insufficiency) is suspected. This may be due to factors such as infertility, abnormal temperature curves, low hormone levels, or abnormal ultrasound findings. They are also measured to detect early menopause, early puberty, timing of ovulation, and signs of masculinization.

The LH/FSH ratio is often calculated when polycystic ovary syndrome (PCOS or PCO syndrome) or masculinization is suspected. In the early phase of the menstrual cycle, FSH and LH levels are measured and the LH/FSH ratio (also called the LH/FSH quotient) is calculated. Normally, a value of less than 2 is expected, but in cases of masculinization and/or PCOS, the value is often greater than 2. The threshold may vary depending on the tests used; some tests specify a lower threshold than 2. In any case, it is common to observe that a high LH/FSH ratio is associated with masculinization or PCOS.

At the onset of menopause, LH levels often increase 4 to 5 times, while FSH levels may increase 10 to 15 times. Consequently, the LH/FSH ratio often falls below 0.7, but the LH/FSH ratio can also be low even before menopause, for example, in anorexia or pituitary disorders. These are just a few examples, as there are other conditions that can affect the LH/FSH ratio.

When analyzing these hormone levels, be sure to consult your health care provider for comprehensive information. Hormone levels can fluctuate significantly, especially during menopause. For a reliable assessment, it is important to consider the timing of the menstrual cycle. For example, when diagnosing PCOS, hormone levels of LH and FSH should be measured between the 3rd and 5th day of the menstrual cycle. In addition, checking the levels three times under consistent conditions is usually recommended.

How is the LH/FSH ratio calculated?

To determine the LH/FSH ratio, the measured LH value is divided by the measured FSH value. With our online calculator, all you have to do is enter your blood values, which you received from your doctor, into the appropriate fields and click on "Calculate". Our calculator will do the rest for you!