Prolactin - All You Need To Know About PRL

Written By Nivetha Arulraj - March 06, 2025

Read Time - 3 min read

Prolactin (‘lact’ means ‘milk’) is known as the ‘milk hormone.’ It is responsible for lactation. Did you think that’s about it for this hormone? Well, you are in for a big surprise! Besides lactation, there are actually more than 300 functions that prolactin impacts, including reproductive, metabolic, regulation of fluids (osmoregulation), regulation of the immune system, and behavioral functions.

What Is Prolactin?

Prolactin, also referred to as luteotropic hormone, is predominantly responsible for breast development and lactation (breast milk production) in mammals along with several other functions related to the immune system, reproductive system, metabolism and much more. It is produced by the anterior pituitary gland, as well as in a variety of regions elsewhere which include the uterus, immune cells, brain, breasts, prostate, skin, and adipose (fat) tissue.

Role Of Prolactin

Production of prolactin is regulated by two key hormones: dopamine (a neurotransmitter produced by the hypothalamus) and estrogen (a class of hormones associated with the female reproductive system). These hormones convey a signal to the pituitary gland, telling it whether to start or stop producing prolactin. While dopamine inhibits prolactin production, estrogen enhances it.
Other hormones can increase and decrease the amount of prolactin released in the body, such as thyrotropin-releasing hormone, oxytocin, and antidiuretic hormone.
For people who have just given birth, a rise in prolactin naturally brings milk production. Breastfeeding or pumping breast milk stimulates prolactin by sending a message to your brain. When you breastfeed, your prolactin levels regulate the milk glands in the breasts to produce more milk and oxytocin takes the responsibility to deliver the milk from the breasts to your baby. As long as you continue breastfeeding often, your body will keep generating prolactin and producing breast milk. ^{1 2}

Understanding Hyperprolactinemia

Fact:

Hyperprolactinemia is a condition of having too much prolactin circulation in the blood. Hyperprolactinemia is found to affect around a third of women in their reproductive years who have irregular periods but normal ovaries.³ High prolactin levels in turn

Results in Galactorrhea (milky discharge from the nipples, not related to breastfeeding women),
Interferes in the production of hormones, thereby, causing disturbance in Ovulation (Process your body goes through while releasing an egg)
Causes difficulty in women trying to conceive

Implication:

High prolactin negatively modulates the secretion of pituitary hormones responsible for gonadal function, including luteinizing hormone and follicle-stimulating hormone and other reproductive hormones which include estrogen and progesterone. As a result, ovulation may be disrupted and this may influence your overall fertility and your ability to get pregnant. High prolactin levels are also associated with a poor uterus lining preparation for embryo implantation.³ Testing your hormones can help ensure there’s nothing interfering in your overall reproductive health.

When Can I Do A Prolactin Test?

Prolactin levels usually fluctuate throughout the day, but are highest in the morning. Thus, it is recommended to take your test within three to four hours after waking up.

What Can Differing PRL Levels Tell You?

1. Normal Prolactin Levels

If you're not pregnant or breastfeeding, your levels of prolactin should be low. The normal level of Prolactin in women ranges between 3 to 27 nanograms per milliliter (ng/mL).

2. High Prolactin Levels

Excessive production of prolactin in the blood results in a condition known as hyperprolactinemia. The condition might also occur due to prolactinoma (one of the types of pituitary tumor). Did you ever wonder why breastfeeding women most often don't become pregnant? Breastfeeding also keeps prolactin levels high and these high prolactin levels may suppress ovulation. Women who are not pregnant or not breastfeeding or post menopausal with high prolactin levels may experience milky discharge from the nipple that indicated a condition called galactorrhea. Prolactin levels in some women are without causing any symptoms. Other concerns associated with high prolactin levels include ^{4 5}

Irregular or absent menstrual periods
A loss of sex drive
Vaginal dryness
Painful intercourse
Acne
Hot flashes
Excess body and facial hair growth
Headaches
Change in vision
Breast tenderness

3. Low Prolactin Levels

Producing little or negligible amounts of prolactin is known as hypoprolactinemia. This condition is rare and is usually associated with an underactive pituitary gland. For those who have just given birth, a drop in prolactin levels in your bloodstream can lead to insufficient milk being produced after giving birth. As such, women with hypoprolactinemia are not known to have specific medical issues like infertility or irregular periods.⁶ Although, a few studies suggest that some women might have slower immune responses. ^{2 7}