Prolactin and Fertility: Everything You Need to Know

You may have heard about the hormone ‘prolactin’ in the context of lactation, but did you know that it’s actually a key ingredient throughout the entire fertility process?  

In this article, we’ll cover everything you need to know about prolactin, including the role that it plays in our reproductive health, what it means if your prolactin levels are too high, and strategies for managing prolactin levels while TTC (trying to conceive). 

Ready? Let’s go!

What is Prolactin? 

Prolactin is a type of sex hormone produced by the pituitary gland (a small structure found at the base of the brain). Its primary function is to prepare breast tissue for lactation and milk production. It also influences other bodily systems such as the nervous system and immune system. 

Among non-pregnant and non-lactating individuals, prolactin levels are typically low. However, certain medications, health conditions, injury, and stress may cause prolactin levels to be abnormally high. 

Among pregnant individuals, prolactin levels rise dramatically throughout pregnancy. Together with estrogen and progesterone, prolactin helps to equip the breasts for breastfeeding. This involves stimulating the growth of breast tissue and preparing cells within the breasts for milk production. 

Immediately after pregnancy, estrogen and progesterone levels drop and the body is ready to begin breastfeeding. Prolactin levels remain elevated after delivery and continue to spike when the nipple is stimulated during breastfeeding. This helps the body regulate milk production. If regular breastfeeding stops, prolactin returns to its pre-pregnancy baseline level within about two weeks. 

Prolactin levels can be tested with a blood test at a doctor’s office. Alternatively, prolactin can also be tested with an at-home finger-prick test – such as Mira’s Panorama Fertility Lab Test which measures five key fertility hormones including prolactin, free testosterone, anti-mullerian hormone (AMH), thyroid-stimulating hormone (TSH), and free thyroxine (fT4). 

Hyperprolactinemia: A Key Factor in Fertility Challenges 

Hyperprolactinemia is a condition characterized by abnormally high prolactin levels. It is relatively rare, with researchers estimating that it affects approximately 1% of the population. Anyone can develop hyperprolactinemia, however, it primarily affects female individuals under the age of 40. 

When prolactin levels are too high, this is often a sign that the pituitary gland and/or the thyroid gland are not working properly. Typically, this is due to either the presence of a tumor in the pituitary gland or an underactive thyroid (also known as hypothyroidism). 

Like other conditions involving a system of hormones, when one hormone is out of balance (in this case prolactin), this can cause other hormones to become out of balance, too. 

For example, among female individuals with hyperprolactinemia, high prolactin levels can affect follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels, when then prevents the ovaries from producing enough sex hormones (such as estrogen and progesterone). This can then lead to irregular cycles, missed periods, anovulation, and ultimately infertility. 

If you are struggling to get pregnant or your menstrual cycles are irregular, it may be worth tracking your sex hormones to see if you have an underlying hormone imbalance. This can be done at home with the Mira App and Monitor, which can measure PdG (pregnanediol glucuronide, the urine metabolite of progesterone), luteinizing hormone (LH), follicle-stimulating hormone (FSH), and E3G (estrone-3-glucuronide, the urine metabolite of estradiol). 

Once you have an idea of what your hormone patterns look like, you can then speak with your doctor for further testing to determine the root cause of any hormonal imbalances. 

Prolactin’s Mechanisms in Female Fertility 

Oocyte maturation

Oocytes are simply immature eggs that exist within follicles on the outside layer of the ovaries. 

At the start of each menstrual cycle, a few oocytes begin to develop or ‘mature’ within their follicles. Once matured, an oocyte is then released from its follicle as an egg through the process of ovulation. 

Research suggests that prolactin is one of the key hormones involved in this egg maturation process, helping to ensure eggs are ready for fertilization. 

Corpus luteum development and functioning

After ovulation, the remaining follicle that released an egg now becomes the corpus luteum – a temporary cluster of cells that produces progesterone. Progesterone then helps to thicken the lining of the uterus to create an environment that is suitable for successful implantation. 

Again, research shows that prolactin may play a significant role in this process by supporting the formation and survival of the corpus luteum. 

Implantation

When an egg has been fertilized by a sperm, it then undergoes the implantation process. This involves the fertilized egg attaching itself to the uterine lining. Once implantation is complete, the pregnancy can continue to develop. 

During this process, research shows that prolactin helps to ensure the uterine lining is a receptive and optimal environment for implantation. 

Effects of High Prolactin Levels on Fertility

When prolactin levels are too high, this causes other fertility hormone levels to be too low resulting in reduced fertility. For example, high prolactin levels inhibit the production of gonadotropin-releasing hormone (GnRH). This in turn limits the production of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which is required for regular ovulation. 

High prolactin levels can also inhibit the production of estrogen and progesterone. 

When estrogen levels are low, this can disrupt the menstrual cycle and limit the growth of the uterine lining – making it difficult for a fertilized egg to implant itself for pregnancy. 

 

When progesterone is low, this can lead to luteal phase deficiency – a condition that also hinders a fertilized egg’s ability to successfully attach itself to the uterine lining. If you have hyperprolactinemia and are actively trying to plan a pregnancy, a great way to monitor progesterone levels is by tracking PdG (the urine metabolite of progesterone) with Mira’s Fertility Max Wands. When tracked over time, you can see whether or not your progesterone levels are elevated enough during the second half of your cycle (i.e. the luteal phase).

On the flip side, if you are pregnant and breastfeeding, high prolactin levels can help to prevent pregnancy within the first six months following birth. In fact, this is considered a method of postpartum contraception known as the lactational amenorrhea method, and it can be up to 98% effective at preventing pregnancy. 

Diagnosing and Treating Hyperprolactinemia 

Hyperprolactinemia can be diagnosed with one or more blood tests at your doctor’s office. In terms of treatment, this will vary depending on the root cause of the elevated prolactin levels. 

If prolactin levels are high due to a tumor in the pituitary gland, the typical first line of treatment is a type of medication called dopamine agonists. Dopamine agonists help to limit prolactin production while also causing the tumor to shrink in size. In rare cases, surgery may be required to remove any tumors that are resistant to medication. 

If prolactin levels are high due to hypothyroidism, your doctor may recommend taking a synthetic thyroid hormone (commonly referred to as levothyroxine). There are not typically any side effects of levothyroxine unless the dosage is too high, in which case you may experience increased sweating, chest pain, headaches, diarrhea, and/or being sick.

Certain medications (such as those that treat pain, nausea, vomiting, depression, psychosis, and high blood pressure), herbs (such as fenugreek, fennel seeds, and red clover), and even lifestyle factors (such as stress, lack of sleep, and excessive exercise) can also cause prolactin levels to be elevated. The best way to assess these factors and their potential impact on your prolactin levels is by visiting your doctor. They will be able to provide the best advice for your individual situation. 

Prolactin and Assisted Reproductive Technology (ART) 

Although there is limited research in this area, there are a few key points to highlight from recent research studies regarding the relationship between prolactin and assisted reproductive technologies (ART). 

Among individuals who have taken dopamine agonists, there is no evidence that suggests that this medication has a negative effect on future IVF (in-vitro fertilization) treatments and outcomes. This is reassuring for patients who have taken dopamine agonists to treat hyperprolactinemia but have hopes to pursue IVF in the future. 

There is also a concept in the medical literature known as ‘transient hyperprolactinemia’. This term is used to describe a temporary increase in prolactin levels during the late follicular phase of a stimulated IVF cycle. In this scenario, research suggests that this slight elevation in prolactin levels may be associated with improved fertility and pregnancy rates – which makes sense considering the role that prolactin plays in oocyte maturation, corpus luteum functioning, and implantation. However, other research studies found that transient hyperprolactinemia was unrelated to IVF outcomes. 

It’s important to remember that research on IVF outcomes, particularly in relation to prolactin, is still limited. The only way to receive the most accurate, personalized advice for your situation is by speaking directly with your doctor and fertility specialist. 

Case Studies and Success Stories 

We love a good success story here at Mira! Take a look at these two inspiring TTC stories involving prolactin management and hyperprolactinemia recovery. 

Rachel Brady: Pregnancy After Prolactinoma

Speaking in a YouTube video, Rachel Brady from the United Kingdom shared her story about getting pregnant after seeking treatment for her elevated prolactin levels. 

Rachel had previously visited a fertility specialist after struggling to conceive. After further testing, she learned that her prolactin levels were too high due to a tumor on her pituitary gland.

In terms of her symptoms with elevated prolactin levels, Rachel shared that she experienced irregular periods. She also noted that her cycle length decreased from 28 days to 22 days. Eventually, she was prescribed bromocriptine (a type of dopamine agonist) and she went on to conceive after only 2 months!  

Love_Taunya: Prolactin Results After Taking Cabergoline

In a fertility update video to her followers, YouTuber Love_Taunya from the United States shared that her prolactin levels were finally back to normal after taking cabergoline (a type of dopamine agonist). 

Previously, Taunya shared that she had visited an endocrinologist to have her hormone levels checked. After blood testing, it was revealed that her prolactin levels were abnormally high and eventually she found the culprit: a tumor in the pituitary gland. 

At her next follow-up appointment, her endocrinologist prescribed cabergoline and within a few months, her prolactin levels were back to normal. 

Taunya shared that she didn’t feel well during the first month or so of taking cabergoline, but the side effects eventually went away and she’s back to feeling great and ready to continue her TTC journey! 

The Interplay of Prolactin and Fertility – Navigating a Path to Parenthood 

From helping oocytes mature in their follicles to enabling new mothers to produce milk for their babies – it’s clear that the sex hormone, prolactin, plays an absolutely crucial role in our reproductive health.

However, too much prolactin in our bodies can lead to an overall hormone imbalance – and this can ultimately hinder an individual’s ability to conceive. More specifically, elevated prolactin levels inhibit the production of estrogen and progesterone, which can cause irregular periods, anovulation, and luteal phase deficiency. 

If you are actively trying to conceive (and especially if you are struggling to conceive), it’s a good idea to make sure your prolactin levels are within a normal change. If they are not, this could be a sign of an underlying hormone imbalance that could potentially interfere with your ability to get pregnant. 

If you do receive a test result that shows your prolactin levels are too high – don’t panic! High prolactin levels (often diagnosed as hyperprolactinemia) can be treated once your doctor has assessed the root cause of the excess prolactin in your body.

The most common causes of hyperprolactinemia include a tumor in the pituitary gland and an underactive thyroid (also known as hypothyroidism). However, numerous other factors such as the medications you’re taking, how much sleep you regularly get, and what your stress levels look like can also cause prolactin levels to appear above the normal range. 

This is why it’s so, so important to seek help from a medical professional if you are struggling to conceive or suspect that your hormones may be out of balance. Whether it’s your GP, a fertility specialist, or an endocrinologist, they will be able to provide you with the best advice and treatment plan based on your lifestyle, medical history, and fertility goals.