Luteinising hormone. A hormone involved in the production of oestrogen in the ovaries and testosterone in the testicles. It is also involved in the ovulation process and the final maturation of eggs. LH levels peak 24 hours – 48 hours before ovulation occurs naturally. LH is often measured during monitoring of ovarian stimulation cycles.

Luteinizing hormone, which may also be abbreviated to LH, is a hormone made by the pituitary gland. This is a small gland located underneath the brain, which influences nearly every part of the human body. Like follicle-stimulating hormone (FSH), the production of this hormone helps to control sexual development and functioning, and as such the two are often tested and have their levels measured together. 

LH is present in both male and female bodies, with differing roles depending on the person’s age:

  • In adult female bodies, LH helps to control the menstrual cycle. It also triggers the release of an egg from one of the person’s ovaries in a process known as ovulation. LH levels rise quickly just before ovulation starts
  • In adult male bodies, LH causes the testicles to make testosterone, which is important for producing sperm cells. Usually, the levels of LH in a male patient will not change much
  • In children, LH levels are normally low in early childhood and only start to rise a couple of years before puberty. LH in female children will signal the ovaries to start producing oestrogen, while it will signal male children’s testes to produce testosterone.

Several different issues may be caused by having too much or not enough LH present in the body. These may include problems with infertility, menstrual difficulties in adult female patients, low sex drive in adult male patients, or early or delayed puberty in children.

Specialists will be able to carry out an LH test to determine the levels of LH present in the blood. These tests may be carried out and used in several different ways, depending on whether the patient is male or female, and an adult or a child. 

For adult female patients, an LH test may be used to:

  • Help find out the causes behind infertility
  • Help find out when ovulation occurs in the patient’s body (to determine the fertility window or the time the person is most likely to get pregnant)
  • Help find out the reason for irregular or stopped menstrual periods
  • Confirm the start of the menopause or the perimenopause (the transition period before menopause)

For adult male patients, an LH test may be used to:

  • Help find out the causes behind infertility
  • Help find out the reason behind a low sperm count
  • Help find out the reason behind a low sex drive

For patients who are children, an LH test may be used to diagnose early or delayed puberty. It may be considered to have come early if it starts before the age of 9 in female children and before the age of 10 in male children. Conversely, puberty may be considered delayed if it does not start before the age of 13 in female children or before the age of 14 in male children.

To carry out an LH test, a specialist will need to take a blood sample using a small needle. This may produce a slight discomfort and bruising in the area where the sample was taken, but should otherwise have no long term side effects. The process itself should take around 5 minutes.