A prolactinoma is a non-cancerous tumor that forms on the pituitary gland, a small organ located at the base of the brain. This tumor causes the pituitary gland to overproduce the hormone prolactin, a condition known as hyperprolactinemia. Elevated prolactin levels can significantly complicate the process of conception by disrupting the reproductive cycle. Despite this challenge, becoming pregnant is highly achievable for most women with a prolactinoma through proper medical management and specialized care.
How Prolactinoma Impairs Fertility
The primary way a prolactinoma interferes with fertility is by chemically suppressing the normal signals required for ovulation. Excess prolactin directly inhibits the release of gonadotropin-releasing hormone from the hypothalamus. This reduces the pituitary gland’s ability to secrete the gonadotropins: luteinizing hormone (LH) and follicle-stimulating hormone (FSH).
LH and FSH are responsible for stimulating the ovaries to develop and release a mature egg. When their levels are suppressed by high prolactin, the ovarian cycle stalls, leading to an absence of ovulation, medically termed anovulation. This hormonal disruption results in irregular or completely absent menstrual periods (oligomenorrhea or amenorrhea). Because regular ovulation is necessary for natural conception, restoring normal prolactin levels is the first step toward overcoming infertility.
Fertility Restoration and Conception Strategies
The most effective strategy for restoring fertility involves the use of specific medications known as dopamine agonists (DAs). These drugs mimic dopamine, which naturally inhibits prolactin secretion from the pituitary gland. By lowering excess prolactin, dopamine agonists shrink the tumor and normalize the hormonal environment needed for ovulation.
The two main medications used are Cabergoline and Bromocriptine, both of which have high success rates, restoring ovulation in over 90% of patients. Cabergoline is frequently preferred because it requires less frequent dosing (often once or twice a week) and is generally better tolerated with fewer side effects like nausea and dizziness. Cabergoline can also be more effective at achieving pregnancy compared to Bromocriptine, with some data indicating higher live birth rates.
Before attempting conception, the prolactinoma must be treated until prolactin levels are within the normal range for several months. For women with a macroprolactinoma (larger than 10 millimeters), treatment is typically continued until the tumor shrinks significantly to minimize the risk of complications during pregnancy. Once prolactin levels are normalized and regular cycles return, the patient can attempt conception naturally. The dopamine agonist is continued until pregnancy is confirmed by a positive blood or urine test.
Monitoring and Managing the Prolactinoma During Pregnancy
Management of a prolactinoma changes immediately after a positive pregnancy test, as the body’s hormonal environment shifts dramatically. Pregnancy naturally causes a surge in estrogen, which can stimulate the growth of the prolactin-secreting cells within the tumor. Tumor enlargement is the main concern during gestation. The risk of symptomatic tumor growth (causing headaches or visual changes) is relatively low, occurring in only about 2% to 3% of women with a microprolactinoma (a tumor smaller than 10 millimeters).
The risk is higher for women with a macroadenoma, ranging from 20% to 30% if the tumor was not significantly reduced before conception. For most women with microprolactinomas or non-invasive macroadenomas, the standard protocol is to discontinue the dopamine agonist treatment immediately upon confirmation of pregnancy. The medication is stopped to limit unnecessary fetal exposure, as the majority of these tumors will not cause problems during pregnancy.
Close monitoring is implemented throughout the pregnancy, focusing on clinical symptoms rather than routine prolactin level checks, which are unreliable due to the natural rise in prolactin from the placenta. Regular check-ups include assessing for new or worsening headaches and performing periodic visual field examinations to check for pressure on the optic nerves. If a woman with a microadenoma develops significant symptoms suggestive of tumor growth, the dopamine agonist can be safely restarted.
For women who conceived while taking a dopamine agonist for a large or invasive macroadenoma, treatment is continued throughout the pregnancy. This continued medical management is a necessary precaution against tumor growth that could compromise vision. Bromocriptine is favored for use during pregnancy due to extensive safety data. Data on Cabergoline is growing, and it is considered safe when medically indicated. If symptoms cannot be controlled by restarting the medication, an MRI scan without contrast may be performed to confirm tumor size. In extremely rare instances, surgery may be considered as a last resort.
Postpartum Considerations
Once the baby is born, the focus shifts to breastfeeding safety and long-term management. Breastfeeding is not thought to cause harmful tumor growth, and women are encouraged to breastfeed if desired. Prolactin levels remain naturally high during lactation, which temporarily complicates tumor monitoring.
If the woman chooses to breastfeed, the medical team advises delaying the restart of the dopamine agonist until lactation has ended. If symptoms of tumor recurrence arise during this time, or if the woman chooses not to breastfeed, the dopamine agonist is typically restarted shortly after delivery.
After the breastfeeding period concludes, follow-up testing is necessary to assess the tumor’s status. This involves checking serum prolactin levels and sometimes repeating an MRI scan now that pregnancy hormones have normalized. For a significant number of women, pregnancy and subsequent hormonal changes can lead to long-term remission, where the prolactinoma may no longer require treatment.