Luteinizing Hormone LH is another important hormone for reproduction. In men, LH promotes secretion of testosterone. In women, LH surge in the second part of the menstrual cycle triggers ovulation. LH is released when a woman is ovulating, and causes the ovaries to release an egg. LH and FSH are closely linked. At the beginning of the menstrual cycle, FSH and LH are secreted to stimulate ovarian follicles. Mid-cycle, the growing follicle will inhibit FSH secretion and increase estrogen. This is a trigger for sudden release of LH that leads to release of the mature egg.
The LH Surge is vital for pregnancy - as it causes the matured egg to be released. The next 24 - 36 hours are the fertile window when a woman can get pregnant. Ovulation Predictor Kits that are available measure LH level in the urine - identifying the best time to conceive. Reduced levels of LH in females indicate ovarian hyperfunction.
LH and PCOS
In females suffering from PCOS - Polycystic Ovarian Syndrome, the LH levels are already elevated when compared to FSH. Since there is no LH surge, ovulation does not take place. Elevated LH levels cause release of androgens from the ovaries leading to acne and Hirsutism. Infertility and miscarriage are common. Studies have shown that there is a direct relation between insulin resistance and elevated LH levels.
In females, the LH levels in the blood can vary based on stage of menstrual cycle, age, pregnancy and other pituitary gland disorders. It can be measured by a blood test or urine test. Usually this test is prescribed for women with irregular periods trying to get pregnant or assessing if a woman has entered menopause. Men with low testosterone levels or having very late puberty are asked to take the LH test.
High levels of Luteinizing hormone are most often caused by ovarian tumors or improperly-developed ovaries. Thyroid or Adrenal disease can elevate LH levels. PCOS and Autoimmune disorders also cause the levels of Luteinizing hormone to rise. Low levels of Luteinizing hormone indicate ovarian failure or primary testicular failure. This can happen due to viral infections such as mumps, autoimmune disorders, radiation exposure and tumors.
Early phase of menstrual cycle: 0.5 to 16.9 IU/L
Peak of menstrual cycle: 8.7 to 76.3 IU/L
Using contraceptives: 0.7 to 5.6 IU/L
Pregnant: less than 1.5 IU/L
Menopause: 15.9 to 54.0 IU/L
Between 20 years and 70 years: 0.7 to 7.9 IU/L
Over 70 years: 3.1 to 34.0 IU/L
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Bibliography / Reference
Collection of Pages - Last revised Date: March 8, 2021