Can High Prolactin Levels Increase Risk of Breast Cancer?

What the latest research on prolactin and breast cancer shows.

Reviewed by Tyler Woods

Key points

• Prolactin is important in normal breast development, pregnancy and breast feeding.
• In studies, women who don't have childbirth have higher prolactin levels.
• High prolactin antipsychotic drug categories have been shown in some studies to increase breast cancer risk.
• Alcohol consumption can increase prolactin levels. Alcohol can increase risk of breast cancer.

Breast cancer is one of the most prevalent cancers among women worldwide, and researchers have long sought to understand the myriad factors that may influence its development. Among these factors, hormones play a critical role, particularly prolactin, a hormone primarily known for its role in lactation. This article explores the relationship between prolactin levels and breast cancer risk, shedding light on current research and potential implications for prevention and treatment.

What is Prolactin?

Prolactin is a hormone produced by the pituitary gland, primarily responsible for stimulating breast milk production after childbirth. However, it also has various other functions, including roles in reproductive health, immune response, and even behavioral regulation. Prolactin levels fluctuate throughout the menstrual cycle and can be influenced by factors such as stress, alcohol intake, sleep, and some medications.

The Role of Prolactin in Breast Tissue

Research indicates that prolactin is not only significant during lactation but also plays a role in the growth and differentiation of breast tissue. Prolactin acts on specific receptors in breast cells, promoting cellular proliferation and differentiation. This action is essential during pregnancy and lactation, but the long-term implications of elevated prolactin levels have raised concerns regarding breast cancer risk.

Prolactin is higher in women who have never had children.

In some studies, nulliparous women (those who never had children), including nuns, have been observed to have elevated levels of prolactin compared to women who have had children. This can be attributed to a lack of regular hormonal fluctuations that occur with menstruation and pregnancy. After childbirth, prolactin levels rise significantly to support milk production. Women who have had multiple pregnancies may have elevated prolactin levels during breastfeeding periods. Some researchers speculate that lower prolactin levels in women who have had childbirth might have a protective effect.

Prolactin and Breast Cancer: The Evidence

The link between prolactin and breast cancer has been explored in various studies, with mixed results. Some research suggests that elevated prolactin levels may be associated with an increased risk of breast cancer. For instance:

• Epidemiological Studies: Some population-based studies have found a correlation between higher prolactin levels and an increased risk of breast cancer. These studies often measure prolactin levels in premenopausal women, who may be more susceptible to hormonal fluctuations.
• Antipsychotic Drugs and Risk of Breast Cancer: Some antipsychotic drugs are well-established to raise prolactin levels. There is some evidence linking high prolactin antipsychotics to breast cancer. Women and girls with high prolactin levels can develop abnormal breast milk, premature breast development, and boys taking antipsychotics can develop disfiguring breast tissue (gynecomastia).
• Cellular Studies: Laboratory studies have demonstrated that prolactin can stimulate the proliferation of breast cancer cells. Prolactin signaling pathways have been implicated in the growth of certain breast tumors, particularly in cases of hormone receptor-positive cancers.
• Animal Models: Research involving animal models has shown that elevated prolactin can lead to the development of mammary tumors.

Mechanisms Behind the Connection

While the exact mechanisms linking prolactin and breast cancer remain under investigation, several theories have been proposed:

1. Cell Proliferation: Prolactin promotes the proliferation of breast epithelial cells. When these cells divide uncontrollably, it can lead to tumor formation. In rodent models, pre-malignant benign breast lesions can be instigated to cancer with high prolactin exposure.
2. Interaction with Other Hormones: Prolactin interacts with other hormones, such as estrogen. Elevated prolactin may enhance the effects of estrogen, which is a well-known risk factor for breast cancer.
3. Genetic Factors: Genetic predispositions may influence how an individual responds to prolactin. Variations in prolactin receptor genes may affect breast cancer susceptibility.
4. Immune Modulation: Prolactin has immunomodulatory effects, and changes in immune response may play a role in cancer development and progression.

Implications for Prevention and Treatment

Understanding the relationship between prolactin and breast cancer could have important implications for prevention and treatment strategies:

• Screening and Monitoring: Regular monitoring of prolactin levels in women, particularly those with a family history of breast cancer or other risk factors, may aid in early detection and prevention strategies.
• Therapeutic Targets: Research into prolactin signaling pathways could lead to new therapeutic options for breast cancer. Drugs that inhibit prolactin or block its receptors may be explored as potential prevention methods or treatments.
• Lifestyle and Dietary Modifications: Since factors like stress and alcohol consumption can influence prolactin levels, lifestyle modifications may help manage hormone levels and potentially reduce breast cancer risk.

Women should generally start getting mammograms at age 40, but guidelines can vary based on individual risk factors. Here’s a breakdown:

1. Average Risk: The American Cancer Society recommends annual mammograms starting at age 40. Women should continue screening until at least age 75, or longer if in good health.
2. Higher Risk: Women with a family history of breast cancer, genetic predispositions (like BRCA mutations), or other risk factors (like those taking high prolactin drugs) may need to start earlier, sometimes as young as 30, and may also need additional screenings like MRIs.
3. Personalized Decisions: It’s important for women to discuss their personal risk factors and family history with their healthcare provider to determine the best starting age and frequency for mammograms.

Regular self-exams and being aware of any changes in breast health are also key components of breast cancer screening. As far as checking prolactin levels, researchers are still working this out. Talk to your doctor if you have concerns.