Prolactin Levels

Last Updated: December 15, 2018

Definition - What does Prolactin Levels mean?

Prolactin levels are used to measure the blood levels of a hormone, called prolactin or PRL, which is produced by a pea-sized gland located at the base of the brain, called the pituitary gland. In women, the hormone is normally produced during pregnancy and after delivery and helps breast development and milk production.

Normal prolactin levels also play a vital role in fertility in both men and women. The normal prolactin levels in nonpregnant women are < 25 ng (nanograms)/mL (milliliters), whereas, in pregnant women, PRL levels are 10-209 ng/mL.

High prolactin levels have a negative impact on fertility potential.

FertilitySmarts explains Prolactin Levels

Prolactin, when released from pituitary binds to its receptor sites. In addition to breast, prolactin receptors are also present in the pituitary gland itself. After binding to its receptors in the pituitary gland, PRL blocks the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary. Since FSH and LH trigger ovulation and enable eggs to develop and mature, blocking them suppresses the normal ovulation process and the fertility potential of a woman.

This means that the higher the prolactin levels, the greater the chances of interrupted ovulation and infertility. For this reason, women who are breastfeeding (and therefore have high levels of prolactin) usually don't get pregnant. It is, however, noteworthy that the PRL levels may drop with the return of ovulation before the menstrual bleeding resumes. Thus, breastfeeding is not a reliable method of birth control.

Several factors can increase PRL levels. In addition to pregnancy and breastfeeding, these include:

  • Sleep
  • Stress
  • Pituitary-gland tumor, called prolactinoma: Releases massive amounts of PRL in blood
  • Drugs used for psychosis and treating nausea and vomiting: These inhibit dopamine release from the brain. Dopamine is a brain chemical that normally suppresses prolactin production from the pituitary gland. By interfering with the dopamine action, these medications interrupt the normal inhibitory action of dopamine on prolactin, resulting in raised prolactin levels
  • Polycystic ovary syndrome (PCOS)
  • Taking estrogen supplements: High circulating levels of estrogen raise prolactin levels by 10- to 20-fold
  • Underactive thyroid gland: The low TSH levels in hypothyroidism trigger the release of thyrotropin-releasing hormone (TRH) from the brain, which in turn, prompts the pituitary to throw more prolactin

Prolactin levels need to be tested if you:

  • Have difficulty getting pregnant
  • Have irregular menstrual periods or no periods at all
  • Have any abnormal nipple discharge without being pregnant
  • Have an abnormal body and facial hair growth
  • Have unexplained headaches or visual impairment (hinting at a prolactinoma)

High prolactin levels can also cause early onset menopausal symptoms, such as hot flashes and vaginal dryness; therefore, pain during sex due to vaginal dryness may also indicate high PRL levels.

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