what is luteinising hormone?
luteinising hormone, usually shortened to lh, is produced by the pituitary gland and works closely alongside follicle stimulating hormone (fsh) to regulate the menstrual cycle and support fertility. it is perhaps best known for the sharp surge that triggers ovulation.
what does lh do?
lh has a few key roles across the menstrual cycle:
- works with fsh to support the growth of ovarian follicles
- triggers a sudden surge in the middle of the cycle that causes the mature follicle to release its egg (ovulation)
- supports the corpus luteum, the structure left behind after ovulation, in producing progesterone
the lh surge
the lh surge in the middle of the cycle is one of the most reliable markers of impending ovulation, which is why it is the basis for many ovulation prediction tests. it typically happens roughly a day or so before an egg is released, in response to rising oestrogen levels from the maturing follicle signalling back to the brain.
lh across the menstrual cycle and life stages
outside of the surge, lh levels are generally lower during the rest of the cycle. lh patterns can also shift with life stage: levels change during puberty as the reproductive system matures, and they typically rise during perimenopause and menopause as the ovaries produce less oestrogen and the usual feedback signals to the brain change.
what influences lh levels?
lh is regulated by the same feedback system linking the hypothalamus, pituitary gland and ovaries as fsh and oestrogen, so anything that disrupts this system can affect lh. this can include certain underlying medical conditions, significant stress, notable changes in body weight, intense exercise, and some medications, including hormonal contraceptives, which work partly by suppressing the natural lh surge.
lh and irregular cycles
an absent or unusual lh pattern can be one of several factors involved in irregular or absent ovulation, which in turn can affect the regularity of periods and fertility. however, lh is just one piece of a bigger picture, and unusual results need proper clinical interpretation rather than assumptions based on symptoms alone.
if you have concerns about ovulation, your menstrual cycle, or fertility, it's a good idea to speak with a doctor or another qualified healthcare professional, who can advise on suitable testing and next steps.