What is an LH test?

Luteinizing hormone is an essential reproductive hormone in the body. Responsible for the growth and development of sex organs in both sexes, the luteinizing hormone (LH), often works in conjunction with the follicle-stimulating hormone (FSH). Both, the LH and the FSH are classified as gonadotropins as they stimulate and maintain the function of gonads, i.e., the testes in the males and the ovaries in the females.

Luteinizing hormone (LH)

The luteinizing hormone is produced in the anterior pituitary gland, which is located below the brain. Chemically a glycoprotein, LH, and the other gonadotropin, FSH is produced by gonadotropin cells in the anterior pituitary. The gonadotropin cells take up about 10-15% of the anterior pituitary gland which is a pea size gland, that forms one of the two lobes of the pituitary gland at the base of the brain.

Mechanism

The Luteinizing hormone is part of the endocrine feedback mechanism which involves the hypothalamus, pituitary gland, and gonads. The gonads are glandular in their physiology and are the reproductive organs of the body. The testes form the male gonad while the ovaries comprise the female gonad. The luteinizing hormone is also known by the terms, lutropin and interstitial cell-stimulating hormone.

During the Development of the foetus

LH levels, typically increase from week 10 to 20 of pregnancy. Although LH levels rise in both foetal sexes during this stage, the gonadal development in males is particularly LH-dependent. In female foetuses, LH levels are much higher as compared to males. But, the gonadal hormones have limited function in the ovaries during intrauterine growth.

Pre-puberty and Puberty

LH levels gradually increase during the pre-pubertal period and continue to increase thereafter. The increased secretion of LH helps in the maturation of the function cells of the gonads.

Males

Increased LH secretion during puberty, results in the increased production of testosterone by the testes. The testosterone hormone is responsible for the production of sperm.

Females

In females, increased LH secretion during puberty results in the increased production of oestrogen by the ovaries.

Role of LH in the menstrual cycle

The LH is vital for the proper regulation of the menstrual cycle throughout your reproductive years of life. LH levels in your body vary according to the different phases of your cycle.

The follicles present in the ovary, grow in conjunction with the increased secretion of follicle-stimulating hormone (FSH) that is produced by the anterior pituitary gland. The growing follicles begin to secrete a hormone called oestrogen. The rising oestrogen levels initiate a negative feedback mechanism which results in a decrease in FSH levels.

Except for one or two dominant follicles, the rest of the antral follicles stop growing and experience regression. The dominant follicle grows in size and continues to mature, continuing to release oestrogen. The rising oestrogen levels initiate a positive mechanism that results in the release of the luteinizing hormone from the anterior pituitary gland.

A peak in your LH levels is followed by the release of the egg from your ovary. This process is known as ovulation which is expected to occur 12 to 36 hours after the LH surge. The dominant follicle then undergoes atresia and forms what is called a corpus luteum.

This results in an increase in progesterone and oestrogen hormone levels, which triggers the shedding of your uterine lining, which is then manifested in the form of menstruation. If you become pregnant, the corpus luteum continues to secrete progesterone. If pregnancy does not occur, the corpus luteum further regresses to form a scar tissue called Corpus Albicans. 

For more information on blood tests, you can read our comprehensive guide.

The Luteinizing Hormone (LH) Test

The LH test measures the levels of luteinizing hormone in your blood. As. The LH levels vary during various phases of the menstrual, the normal ranges for each phase of the menstrual cycle are considered separately.

Normal Range of LH levels

The normal range of luteinizing hormone (LH) levels is as follows:

Females

• Follicular Phase: 1-12 IU/L
• Ovulation Phase: 16-104 IU/L
• Luteal Phase: 1-12 IU/mL
• Menstruation: 1.37-9 IU/L
• Post-menopause: 16-66 IU/L

Males

Men: 1-8 IU/L

The LH test involves taking a venepuncture to draw your blood sample to measure the LH levels in your body. Your doctor may sometimes advise repeating the test during different phases of your cycle, to check for the rise and fall of your LH levels.

Why should you test your LH levels?

If you are having irregular menstruation, measuring hormones that regulate your menstrual cycle could help to detect the cause of amenorrhea. An LH may also be advised in the case of primary amenorrhea, which is the delay of your first period. 

Delayed puberty among males, may also call for an LH test.

Detecting the monthly peak in your LH levels can be pretty useful when you are trying to conceive. Your LH levels typically surge, 12 to 36 hours before ovulation. Testing your LH levels can help to time your intercourse according to your LH peak, and the ovulation that is to occur. Apart from a blood test, LH levels in your urine can also help to predict your ovulation. You may consider using an Instant Ovulation Test and thereby take the urine test by yourself at home. 

In the case of infertility, i.e., when a couple has had unprotected intercourse for 12 consecutive months and have not conceived, your doctor may recommend doing a basic reproductive health checkup.  This includes your LH, FSH, estrogen, TSH, and prolactin levels.

Irregular Periods during perimenopause may call for a visit to the doctor. A menopause blood test that also includes an LH test may help to understand the stage of your menopause. After menopause, LH levels are usually high.

High levels of LH have been observed among women who suffer from anovulation, PCOS, or genetic disorders such as Turner syndrome.

High levels of LH in males is associated with infertility, increased alcohol consumption, Klinefelter’s syndrome, or a history of chemotherapy or radiation.

Low LH levels in women is associated with poor nutrition, over-exercising, or maybe indicative of an underlying pituitary disorder.

Low LH levels in males

Low LH levels in males is associated with pituitary dysfunction or Kallmann syndrome.

Conclusion 

You should check you LH levels with an LH Test if you are worried about your health, you should always talk to your doctor first before trying any medication or if you have any health concerns.