LH and FSH
Two pituitary hormones that drive ovulation. In PMOS their balance is often skewed toward LH, part of why ovulation stalls.
LH (luteinising hormone) and FSH (follicle-stimulating hormone) are released by the pituitary gland and together drive the menstrual cycle. FSH helps follicles in the ovary mature; a surge of LH triggers ovulation, the release of the egg.
Their balance matters as much as their levels. In PMOS, fast GnRH pulses from the hypothalamus push the pituitary toward releasing relatively more LH than FSH. With less FSH support, follicles do not mature fully, and without the right LH surge in the right rhythm, ovulation may not happen.
An LH-to-FSH ratio is sometimes mentioned in PMOS, but it is not a diagnostic criterion on its own and is not reliable enough to diagnose or rule out the condition. It is one part of the larger HPO axis picture.