LH (luteinizing hormone, lutropin) and FSH (follicle stimulating hormone, follitropin) are gonadotropic hormones which are glycoproteins produced by the pituitary. The ratio of LH to FSH is increased in many cases of the polycystic ovary syndrome.


Specimen Collection:

(1) FSH and LH levels may be affected by episodic (pulsatile) or cyclic secretion and/or diurnal variation.

(2) Pooling (equal volumes) of multiple serum samples collected during the day may give more reliable results than a single serum sample.

(3) Timing of collection relative to menstrual cycle is important for evaluation in women.

Timing of Sample

Reference Range FSH in mIU/mL (Tietz)

Reference Range LH in mIU/mL (Tietz)

follicular phase



ovulatory peak



luteal phase







Polycystic ovary syndrome:

(1) LH levels tend to be high normal or increased.

(2) FSH levels tend to be low normal or decreased.

(3) The ratio of LH to FSH tends to be increased.

(4) Chronic anovulation develops at puberty.

(5) Increased ovarian androgen levels may result in mild hirsutism, amenorrhea or virilization.

(6) Stein-Leventhal syndrome: enlarged polycystic ovaries, obesity and amenorrhea.


Changes in hypogonadism:

(1) Hypogonadism due to hypothalamic or pituitary problems is associated with decreased FSH and LH levels.

(2) Hypogonadism due to an ovarian gonadal defect are associated with increases in both FSH and LH.


LH-to-FSH ratio =

= (LH) / (FSH)



• LH and FSH are in mIU/mL in conventional units or IU/L in SIU (conversion factor 1.0)



• The ratio is increased in the polycystic ovary syndrome; cutoffs of > 1.5 or > 2.0 may be used.


To read more or access our algorithms and calculators, please log in or register.