Prolactin (also known as PRL) isn't a word you'd necessarily come across in casual conversation, but it's actually super important when you're talking and thinking about fertility. If you've never heard of prolactin, have no fear! Read on to find out more.
We say prolactin, you say... what?
Prolactin is the ‘milk hormone,’ responsible for breast milk production, also known as lactation. (Fun fact: "lact" means "milk," it's from the Latin, lactare - "to suckle." Prolactin literally promotes the making of milk.) But prolactin is no one trick pony - besides lactation, there are actually more than 300 functions that prolactin impacts, including reproductive, metabolic, regulation of fluids (osmoregulation), regulation of the immune system (immunoregulation), and behavioral functions. Your prolactin is produced and stored by and in the pituitary gland, as well as in the uterus, immune cells, brain, breasts, prostate, skin, and adipose (fat) tissue.
Estrogen (a group of hormones including estriol, estradiol, and estrone) also regulate prolactin. Other hormones can increase and decrease the amount of prolactin released in the body, such as dopamine, thyrotropin-releasing hormone, oxytocin, and anti-diuretic hormone. For people who have just given birth, a rise in prolactin naturally beings milk production. Breastfeeding or pumping breast milk sends a signal to your brain to stimulate prolactin. The prolactin hormone helps milk glands in the breasts know to produce milk.
What if I have too much prolactin?
If you're not pregnant or breastfeeding, your levels of prolactin should be low. Having too much prolactin in your bloodstream results in a condition known as hyperprolactinemia. These high prolactin levels can result in the inhibition of secretion of FSH (or follicle-stimulating hormone). Because of this, high prolactin levels may suppress ovulation. Breastfeeding also keeps prolactin levels high and estrogen levels low. If you’ve ever heard that breastfeeding individuals don’t often become pregnant, this is why (although it is still possible, especially if you aren't exclusively breastfeeding.)
High levels of prolactin unrelated to breastfeeding could indicate galactorrhea, which results in milky nipple discharge, irregular or absent menstrual periods (which impacts fertility since ovulation is inconsistent or gone entirely), a loss of sex drive, vaginal dryness, and painful intercourse. Galactorrhea can be caused by certain medications like antidepressants and antipsychotics, as well as those for high blood pressure, some herbal supplements, birth control pills, and conditions like benign pituitary tumors (prolactinomas), and underactive thyroid (also known as hypothyroidism), chronic liver and kidney disease, and even excessive breast stimulation. People with PCOS may have slightly elevated levels of prolactin. If you're taking Modern Fertility's hormone test, it's recommended that you avoid breast and nipple stimulation (that's right: nipple stimulation can affect your hormones! Wild, right?) as well as sex before testing so that your prolactin levels can register accurately. You don't have to have given birth to have galactorrhea and it's also been found in post menopausal women.
The underlying cause of excess levels of prolactin dictates the treatment of it. If you have a prolactinoma, your doctor may perform surgery to remove it, and/or prescribe bromocriptine or cabergoline (dopamine promoters), which decrease prolactin levels when one has a tumor, and also when the cause for hyperprolactinemia can't be determined.
And too little?
Having low levels of prolactin, on the other hand, is known as hypoprolactinaemia. This condition is rare and is usually associated with an underactive pituitary. For those who have just given birth, a decrease in the amount of prolactin in your bloodstream can lead to insufficient milk being produced after giving birth. Most people with low prolactin levels do not have any specific medical problems, although there is some evidence of reduced immune system responses with low levels of prolactin post birth.
If you’re curious about your prolactin levels, Modern Fertility can help. Our tests give you a handle on the hormones that impact fertility, including prolactin. It’s information you can use to be a prolactin pro!