Prolactin is a hormone produced by the pituitary gland, a small organ at the base of the brain, and its best-known function is stimulating milk production in new mothers. When prolactin levels become abnormally high, a condition known as hyperprolactinemia, it frequently interferes with a woman’s reproductive cycle. While this can cause temporary infertility, pregnancy is often successfully achieved once the underlying cause is identified and managed with appropriate medical intervention.
The Link Between High Prolactin and Ovulation
Elevated prolactin directly impacts the hormonal cascade that controls a regular menstrual cycle and ovulation. Prolactin acts on the hypothalamus, the control center in the brain, to suppress the release of Gonadotropin-Releasing Hormone (GnRH).
The decrease in GnRH then causes the pituitary gland to reduce its production and secretion of two other hormones: Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH). These gonadotropins are essential for stimulating the ovaries to mature an egg and trigger its release. A lack of sufficient LH and FSH prevents the ovary from preparing and releasing an egg, a condition called anovulation.
Anovulation is the direct reason for infertility associated with high prolactin, often resulting in irregular or absent menstrual periods (amenorrhea). This hormonal disruption effectively suppresses the reproductive system, mimicking the state of lactation.
Identifying the Causes of Hyperprolactinemia
The reasons behind elevated prolactin levels are diverse, spanning physiological, pathological, and pharmacological sources. The most common pathological cause is a prolactinoma, a benign, prolactin-secreting tumor on the pituitary gland. These tumors are classified as microadenomas or macroadenomas and are diagnosed with blood tests and magnetic resonance imaging (MRI) scans.
Certain medications can also induce hyperprolactinemia by interfering with the brain’s dopamine pathways. Since dopamine is the primary inhibitor of prolactin release, drugs like some antipsychotics, antidepressants, and certain blood pressure medications can inadvertently raise prolactin levels. Addressing this cause may involve working with a physician to adjust or switch prescription drugs.
An underactive thyroid gland, or hypothyroidism, is another common cause. When thyroid hormone levels are low, the body increases the release of thyrotropin-releasing hormone (TRH), which stimulates the pituitary. TRH also acts as a prolactin-releasing factor, causing a simultaneous elevation in both Thyroid-Stimulating Hormone and prolactin.
Medical Pathways to Conception
The primary goal of treatment is to normalize prolactin levels, which restores the release of GnRH, LH, and FSH, allowing ovulation to resume. The most effective approach involves dopamine agonists, which mimic dopamine to suppress prolactin production directly at the pituitary gland. Medications like Cabergoline and Bromocriptine are the standard first-line therapies.
Cabergoline is often favored due to its higher efficacy, better tolerability, and less frequent dosing schedule compared to Bromocriptine. These medications are highly successful, restoring ovulatory cycles in approximately 80 to 90 percent of patients. Once prolactin levels drop into the normal range, ovulation typically resumes within weeks to months, making conception possible.
If hyperprolactinemia is secondary to hypothyroidism, initial treatment focuses on managing the thyroid condition with hormone replacement therapy. Correcting thyroid function frequently results in a natural reduction of elevated TRH and prolactin levels. In cases where no clear underlying medical cause is found, managing factors like chronic stress or excessive exercise may also support the return to normal hormonal balance.
Monitoring Prolactin Levels After Pregnancy is Achieved
Once conception occurs, the management of hyperprolactinemia shifts, focusing on maintaining the pregnancy. For women with microprolactinomas or non-compressive macroadenomas, the general recommendation is to discontinue the dopamine agonist medication immediately upon confirmation of pregnancy. The risk of significant tumor growth during pregnancy is low, about two to three percent for microadenomas.
This change in protocol is due to the natural rise in estrogen during pregnancy, which stimulates the growth of prolactin-producing cells. Women with existing macroadenomas face a higher chance of tumor enlargement, potentially causing symptoms like severe headaches or visual disturbances. If these symptoms appear, the dopamine agonist will be re-introduced to shrink the tumor.
Clinical monitoring throughout the pregnancy focuses on symptom surveillance rather than routine prolactin measurement or MRI scans. Prolactin levels naturally soar during pregnancy in preparation for lactation, making a blood test uninformative for monitoring the underlying condition. Women are instructed to report any symptoms of pressure, such as changes in vision or persistent headaches, to their endocrinologist or obstetrician immediately.