What is LH (Luteinising Hormone)?: A quick guide

What is LH?

Throughout IVF you will be subject to a huge number of medications, all which contain a variety of synthetic hormones. One of which is LH (luteinising hormone)

Luteinising hormone (LH) is produced in the anterior pituitary gland by gonadotropic cells.

In women it works in sync with Follicle Stimulating hormone (FSH) and an LH surge causes the development of a temporary part of the ovary called the corpus luteum. This stimulate progesterone and oestrogen production and is present in the luteal phase of a woman’s menstrual cycle. It also triggers ovulation.

In men LH is produced in the same place as women. It is important in the release and regulation of testosterone. In simple terms it creates a negative feedback loop which either inhibits or encourages the release of Testosterone. It does this by acing upon the Leydig cells, which, are the cells which create testosterone in the testes.

What is the structure of LH?

LH is a monomeric glycoprotein hormone with two subunits. One subunit is the same as with FSH and hCG but the 2nd one is different. This 2nd unit is what gives it it’s distinct properties and allow it to react with LH receptor. It has a short time to act as it only has a biologic half-life of 20 minutes.

What are normal Levels of LH?

Females – LH levels in general start very low in children, increase to the normal levels as the women reaches puberty and through her reproductive years and then become high once she enters the menopause. LH levels in women of reproductive age are normally between 1 – 20IU/L with a serious high peak for 48 hours during ovulation. After which it returns to normal. See the graph oppsite for a detailed understanding of LH through teh menstraul cycle.

Males – In men over 18 the normal range oh LH is between 1.8–8.6 IU/L

What medical conditions impact LH?

In terms of fertility having too much or too little can seriously impact your fertility.

The most common conditions which can cause elevated levels of LH are

  • PCOS
  • Turner Syndrome
  • A problem with your pituitary gland

A high level of LH can increase levels of testosterone in women which can lead to infertility or subfertility.

A couple of causes of low levels of LH are:

  • Hypopituitarism
  • Eating disorder

How can LH be used whilst trying to conceive?

The spike in LH during the ovulation window allows women to track their ovulation fairly effectively. There are a number of ovulation prediction kits on the market which measure the level of LH in the urine. When the tests show a negative, it is picking up very low levels of LH in the urine and you aren’t ovulating. When you get a positive it spot’s the increase in LH in the urine and this indicates that you will ovulate within 24-48 hours.

It is important to note that often people mis-read or misunderstand LH OPK tests because in a pregnancy test any line is positive, but this is NOT the case in an ovulation stip. The line has to be the same colour or darker than the control line as shown in the image by Pregmate opposite.

 

These should be used for 3-5 days before your expected date of ovulation. They can be very helpful for women who have irregular periods, or non-even menstruation (i.e. a long or short luteal phase) as it can be harder to predict when ovulation should occur.

The one downside of ovulation testing from a trying to conceive perspective is that if you only have sex when you get that positive test you will have missed a couple of days as your fertile period starts a couple of days before the positive LH test. As such you should try to have sex every 2-3 days whilst trying to get pregnant, but a LH OPK can be a useful tool. However, it is important to note if you have a condition where you have elevated LH (e.g. PCOS) ovulation strips are not always accurate due to a long standing increase in LH – alternative ways of monitoring for ovulation could be basal body or core temperature.

How is LH used in IVF and assisted reproduction?

For information about all the medications used in IVF check out our article.

LH is a gonadotrophin, as is FSH. The main use of LH is in the stimulation phase of IVF. There are two types of stimulation drugs, Follitropins and human menopausal gonadotrophins (hMG). The only ones that contain LH are hMG’s, these contain a mixture of LH and FSH. The most common brands in the UK include Menopur and Merional.

These medications stimulate follicular growth and maturation, so that you produce a number of mature follicles which can then be have their eggs retrieved and to thicken the endometrial lining ready to receive an embryo. This process usually lasts for 7-12 days and is dependent upon how the woman responds to the medication in terms of follicle development and endometrial lining.

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