LH is also known as luteinizing hormone. Luteinizing hormone is actually present in both sexes, and is made by the front part of the pituitary gland (also known as the anterior pituitary). Luteinizing hormone binds to the gonads and has its effects there. It's made up of two separate protein subunits with a small chain of sugar groups attached. The sugars affect how long luteinizing hormone stays in the body, although it typically has a half-life of about 20 minutes (which means that half of the hormone is gone within 20 minutes). In males, luteinizing hormone causes the production of testosterone, whereas in females it affects estrogen and progesterone levels.
Effects on Estrogen
In females, luteinizing hormone works on the ovaries--where it makes its effects by changing the levels of estradiol (which is the predominant form of estrogen) and progesterone. Luteinizing hormone secretion is increased as a result of increased levels of estradiol (which normally occurs as a result of higher levels of a hormone called follicle-stimulating hormone). Luteinizing hormone also causes increased elevated estrogen levels, which leads to a quickly escalating cycle: More estrogen leads to more luteinizing hormone, which in turn leads to more estrogen. Ultimately, luteinizing hormone levels surge, causing a follicle within the ovaries to fully mature and causing a rapid increase in estrogen levels.
Effects on Progesterone
Luteinizing hormone also affects progesterone levels, although this effect is more indirect. When an ovarian follicle matures and releases an egg (as a result of luteinizing hormone stimulation), the remaining tissue becomes a structure called the corpus luteum. The corpus luteum is responsible for making and secreting progesterone. Progesterone is used to help prepare the uterus to accept a possible pregnancy. Thus, shortly after triggering the release of an egg, luteinizing hormone also increases progesterone levels to prepare the uterus.