What is LH?
Luteinizing hormone (LH) test measures its level in your blood. LH is a hormone produced by the pituitary gland that plays a key role in both the male and female reproductive systems. LH works closely with another hormone called follicle-stimulating hormone (FSH) to control sexual functions. Therefore, FSH level is often measured along with LH.
If a woman is trying to become pregnant, the doctor might want to get an LH test multiple times to pinpoint the timing of egg release and increase the chances of conception. This test is also used to diagnose causes of infertility in males as well.
Why is LH done?
The following could be reasons why LH test is advised by your physician:
Infertility in women (difficulty in getting pregnant)
Irregular menstruation in women
Absence of menstrual periods (amenorrhea) in women
Polycystic Ovary Syndrome in women
Infertility in men
Conditions affecting pituitary gland in men and women
Conditions affecting the hypothalamus in men and women
Low testosterone level in men
Low sex drive in men
Low muscle mass in men
Underdeveloped or absent testicles in men
What does LH Measure?
Luteinizing hormone is associated with reproduction and ovulation. In females, it stimulates the release of an egg from the ovary. However, in males, testosterone production is dependent on LH. This test helps in measuring the amount of LH present in the blood.
LH is produced by the pituitary gland, and its production is controlled by the hypothalamus, pituitary gland, and the hormones produced by the ovaries (in women) or testicles (in men).
In premenopausal women, LH stimulates ovulation and the production of other hormones, estradiol, and progesterone. The menstrual cycle is divided into 2 phases, follicular and luteal phases, each of these last for about 14 days. Near the end of the follicular phase, there is a mid-cycle increase in follicle-stimulating hormone (FSH) and LH. This triggers ovulation. During the luteal phase, LH secretion stimulates the corpus luteum to start producing progesterone. At this point, FSH and LH levels get reduced, while progesterone and estradiol concentrations rise. If the egg is not fertilized, then the levels of these hormones fall after several days followed by the beginning of the next menstrual cycle. With the onset of menopause ovarian function reduces and eventually discontinues, which results in increased levels of FSH and LH.
In men, LH stimulates Leydig cells in the testicles to produce testosterone. However, LH levels remain relatively constant in men after puberty. A high testosterone level provides negative feedback to the pituitary gland and the hypothalamus, thus decreasing the amount of LH secreted.
In infants and children, LH levels rise shortly after birth and then fall to very low levels (by 6 months in boys and 1-2 years in girls). At about 6-8 years of age, levels again rise before the beginning of puberty and secondary sexual characteristics development.
Interpreting LH results
The following values are considered to be normal, LH blood levels measured in international units per liter (IU/L):
· Follicular phase of the menstrual cycle: 1.9 to 12.5 IU/L
· LH surge: 8.7 to 76.3 IU/L
· Luteal phase of the menstrual cycle: 0.5 to 16.9 IU/L
· Pregnancy: less than 1.5 IU/L
· Post-menopause: 15.9 to 54.0 IU/L
· Women using contraceptives: 0.7 to 5.6 IU/L
· Age group of 20 and 70 years: 0.7 to 7.9 IU/L
· >70 years of age: 3.1 to 34.0 IU/L
Reference values may vary from lab to lab*