LH (Luteinizing Hormone)
Definition
A hormone that controls sexual development and fertility. In menstruating women it triggers ovulation and regulates the cycle. In men it stimulates the production of testosterone needed for sperm formation.
Purpose
- In women: Infertility workup, monitoring the timing of ovulation, irregular/absent periods, menopause/perimenopause evaluation, ovarian disorders
- In men: Infertility, low sperm count, low testosterone, reduced sex drive, testicular disorders
- In both: Diagnosis of pituitary or hypothalamic dysfunction
- In children/adolescents: The cause of early or delayed puberty
Results
Abnormally high LH in women → PCOS, premature ovarian insufficiency or approaching menopause. High LH in men → testicular damage or dysfunction. Low LH → a pituitary or hypothalamic problem. High LH in children with signs of early development → central precocious puberty; normal LH → peripheral precocious puberty.
Normal Values
Laboratory-specific.
Risks and Limitations
Timing is critical: If you menstruate, you may need to have the test done at a specific time in your menstrual cycle. Because LH fluctuates throughout the month, the result must be interpreted with the cycle phase in mind.