LH (luteinising hormone), also known as lutropin, is an important fertility hormone which affects your ability to ovulate. It is produced in the pituitary gland and is the hormone ovulation tests measure to determine when you will be ovulating.
LH has an important role throughout your entire menstrual cycle. In the first two weeks of your cycle it is responsible for the maturation of your egg. It does this by stimulating your ovaries to produce the necessary amounts of oestradiol (an estrogen hormone) for egg maturation. On day 14 of your cycle, LH levels will surge which triggers your ovaries to release your egg. We more commonly call this our ovulation day and you can use our ovulation calculator to find out when yours is. In weeks 3 and 4 of your menstrual cycle (or weeks 1 and 2 of pregnancy), LH is in charge of the development of the corpus luteum, the structure which ensures your body produces enough progesterone to maintain a pregnancy if fertilisation occurs. If you become pregnant your LH levels will drop and hCG will ensure that your body produces sufficient levels of progesterone.
Excessively high or low levels of LH can cause fertility problems in both men and women. So if you are having trouble conceiving your physician will probably test both you and your partner’s LH levels.
Good news mums! Since LH levels drop during pregnancy, this hormone does not cause any pesky pregnancy symptoms.