What is Luteinizing Hormone (LH)?

LH is an acronym which stands for Luteinising Hormone. Hormones are chemicals in your body that are made in one place and are used in another. As the name suggests, LH is responsible for luteinising the mature follicle in your ovaries after ovulation.  It is one of the two gonadotropins (so called because it stimulates the gonads), the other being its partner, FSH, which stands for follicle stimulating hormone.  LH and FSH are secreted by the pituitary gland, a small pea-shaped gland below the base of your brain.  LH is necessary for fertility. In women, LH helps regulate ovulation. In men, LH helps the testes to make and secrete testosterone.

LH levels vary during the menstrual cycle, and peak prior to ovulation. In fact, it is the surge of LH production ( called the LH surge) which induces ovulation in a normal woman. It is this LH surge which is measured by the home ovulation test kits ( OPKs, ovulation prediction kits) which check for LH levels in the urine.

What is the Luteinizing Hormone Test?

The LH test is a simple blood test . It is typically measured on Day 3, along with the FSH testand the estradiol test.

What do the Results Mean?

On Day 3, normal LH values are between 3 and 10 mIU/mL. LH levels can also be artificially raised by ovulation inducing drugs such as clomiphene citrate ( clomid).

Low levels of LH ( less than 2 mIU/ml) are found in a condition called hypogonadotropic hypogonadism. Women on birth control pills as well as pregnant women also have low levels of FSH.

LH levels are usually interpreted in conjunction with the FSH levels. Normally, the ratio is 1, which means the FSH level and LH level are approximately the same. In patients with polycystic ovarian disease ( PCOD) , this ratio is reversed; and patients with PCOD typically have a high LH level and a normal FSH level. This is called a reversal of the FSH:LH ratio; and in  patients with PCOD it is 2 or more.

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