Polycystic Ovary Syndrome (PCOS) is a frequent endocrine disorder affecting women of reproductive age. It is characterized by an excess of male hormones, irregular menstrual cycles, and small cysts on the ovaries. Many individuals with PCOS also exhibit elevated levels of the hormone prolactin, a condition known as hyperprolactinemia. This finding is often puzzling, as prolactin is primarily associated with lactation.
Understanding Prolactin and PCOS
Prolactin is a peptide hormone produced and secreted by the pituitary gland, a small, pea-sized structure located at the base of the brain. Its most well-known function is stimulating the production of breast milk, but it also plays a role in regulating the reproductive system. The secretion of prolactin is normally kept in check by the neurotransmitter dopamine, which acts as a constant inhibitor.
PCOS is a complex endocrine and metabolic disorder. The condition is diagnosed when a patient exhibits at least two of the three main features: excess androgens (hyperandrogenism), irregular or absent ovulation (anovulation), and the presence of polycystic ovaries on ultrasound. These hormonal disruptions lead to a cascade of symptoms like hirsutism, acne, and difficulty conceiving.
The Physiological Link Between PCOS and High Prolactin
The most accepted explanation for elevated prolactin in PCOS involves dysfunction in the hypothalamic-pituitary axis, the body’s central hormone control system. The primary theory centers on a disruption of the normal inhibitory control exerted by dopamine. Evidence suggests that in women with PCOS, there may be reduced dopaminergic signaling, which lessens the suppression of the pituitary gland, thus leading to a mild increase in prolactin secretion. This reduced inhibitory effect is considered a significant factor connecting the two disorders.
A second, and highly prevalent, mechanism involves the metabolic dysfunction common to PCOS, specifically insulin resistance and hyperinsulinemia. High levels of insulin, which result from the body’s diminished response to the hormone, may directly stimulate the pituitary gland to release more prolactin. Hyperinsulinemia, a hallmark of PCOS, may also interfere with the hypothalamic regulation that normally keeps prolactin levels low.
Estrogen levels, which can be moderately elevated in some PCOS patients due to the continuous conversion of androgens in fat tissue, also play a part. Estrogen is known to stimulate the production and release of prolactin from the pituitary gland. This interplay of metabolic and hormonal factors solidifies the biological link.
Recognizing the Symptoms of Hyperprolactinemia
While PCOS itself causes significant menstrual irregularities, high prolactin levels can exacerbate these issues, often leading to more pronounced amenorrhea (the complete absence of a menstrual period). Hyperprolactinemia suppresses the release of gonadotropin-releasing hormone, which inhibits ovulation and normal menstrual cycling. This makes conception difficult for many women with this dual diagnosis.
Another distinguishing symptom directly caused by elevated prolactin is galactorrhea, the production of a milky discharge from the nipples when a woman is not pregnant or nursing. This is a clear clinical sign that warrants prolactin testing. High prolactin levels can also cause a decline in sex hormone production, leading to symptoms like decreased libido and vaginal dryness. Recognizing these specific signs helps medical professionals differentiate symptoms caused by prolactin from the general androgen-related issues of PCOS.
Evaluating Other Causes of Elevated Prolactin
It is important to remember that PCOS is only one potential cause of hyperprolactinemia, and a medical evaluation must rule out other, sometimes more serious, conditions. The most common pathological cause is a prolactinoma, which is a benign tumor of the pituitary gland that secretes prolactin. Very high prolactin levels, often exceeding 200 ng/mL, typically point toward a prolactinoma, requiring imaging like an MRI for confirmation.
Certain medications are also frequent culprits in raising prolactin levels. Drugs such as some antipsychotics, certain antidepressants, and anti-nausea medications can block the action of dopamine, thereby removing the suppression on prolactin secretion. Primary hypothyroidism, an underactive thyroid, can also elevate prolactin. A comprehensive diagnosis requires testing for these alternative causes, including thyroid function and a review of all current prescriptions, before confirming that PCOS is the primary driver.
Treatment Approaches for High Prolactin in PCOS
Management of high prolactin in the context of PCOS involves a two-pronged strategy: addressing the underlying PCOS pathology and directly lowering prolactin levels. Indirect treatment focuses on mitigating the metabolic dysfunction, particularly insulin resistance. Medications like metformin, which improve insulin sensitivity, can indirectly reduce circulating prolactin levels by interrupting the hyperinsulinemia-prolactin link. Lifestyle changes, including dietary adjustments and regular exercise, also serve this indirect function by improving the body’s response to insulin.
For direct prolactin suppression, or when fertility is a significant goal, dopamine agonists are the standard treatment. These medications, such as cabergoline or bromocriptine, work by mimicking the action of natural dopamine, thereby restoring the inhibitory signal to the pituitary gland. Cabergoline is generally preferred due to its higher efficacy in normalizing prolactin and its less frequent dosing schedule, which improves patient adherence. The combination of a dopamine agonist with metformin has been shown to be superior to metformin alone in regulating menstrual cycles and reducing prolactin levels.