Prolactinoma Complete Overview

What is Prolactinoma? 

• A prolactinoma is a benign (non-cancerous) tumor that forms in the pituitary gland.This leads to the overproduction of prolactin hormone.50% of prolactinomas are small in size. They are called microprolactinomas (less than 1 cm or 3/8th of an inch in diameter). 
• Microprolactinomas are more commonly diagnosed in females due to the disruption of menses by hyperprolactinemia. Larger prolactinomas are usually found in males and are diagnosed at a later age due to the lack of symptoms. They are larger than 1 cm or 3/8th of an inch and are known as macroprolactinomas.

What is Prolactin Hormone?

• Responsible for the development of mammary glands within the breast tissue.
• Facilitates lactation and milk production.
• Prolactin levels are low among males and non-lactating and non-pregnant women.
• Prolactinomas can cause increased blood prolactin levels which can lead to several health issues, including infertility. Elevated prolactin levels inhibit secretion of FSH and LH, leading to an ovulation and decreased production of estrogen.

What are the Causes of Prolactinoma?

• The actual cause of prolactinoma is usually unknown as they are sporadic.
• Prolactinoma may occur as a part of Multiple Endocrine Neoplasia type 1 (MEN 1), which is an inherited condition.
• Microprolactinomas are more common among females, and macroprolactinomas are more common among males.

Epidemiology

• These non-cancerous pituitary tumors are common in the general population.
• Studies show that 30-40% of pituitary adenomas are prolactinomas.
• Hence, they can be considered as the most common type of pituitary tumor.
• More than 90% of clinically diagnosed prolactinomas are microplactinomas, and they are much more common than macroplactinomas.
• About 1 in 10,000 people have a prolactinoma.
• Prolactinoma can occur in all sexes at any age.
• But it is more common in women between 20 to 50 years of age.

How Can we Diagnose Prolactinoma?

Clinical features

Clinical Presentation of Prolactinoma in Females

• Changes in menstruation which are not related to menopause. This includes irregular periods (menstruation) or no periods (amenorrhea).
• Milky discharge from nipples when the woman is not pregnant or breastfeeding (galactorrhea).
• Loss of interest in sex.
• Infertility.
• Vaginal atrophy which can lead to pain while having penetrative sex.
• Decreased bone mineral density.

Clinical Presentation of Prolactinoma in Males

• Erectile dysfunction.
• Infertility.
• Low levels of testosterone which leads to decreased libido.
• Galactorrhea.
• Enlarged breast tissue (gynecomastia).

Clinical Presentations in case of Large Prolactinomas

• Nausea and/or vomiting.
• Sinus pain or pressure in the sinus.
• Headaches.
• Problems with olfactory sense.
• Vision changes (double vision or decreased peripheral vision [bitemporal hemianopsia]).

The signs and symptoms of prolactinomas can vary depending upon the following factors:

• How much excess prolactin is produced by the pituitary gland
• Size of the prolactinoma
• Location

Male individuals and women who have reached menopause may not have any overt signs and symptoms. Thus, diagnosis is delayed among these groups.

Investigations

Prolactinomas are usually detected at an earlier stage in genotypic females due to irregular periods. The following tests are used to diagnose a prolactinoma:

Prolactin Level Blood Test

• This test helps quantify the prolactin level in the blood.
• If it is elevated beyond the normal range, imaging is advised to look for a possible prolactinoma.

MRI (Magnetic Resonance Imaging) Scan

• The imaging test that is preferred to diagnose a prolactinoma is an MRI.
• It can help delineate the location and size of the prolactinoma.

CT (Computed Tomography) Scan

• CT scan is recommended if an MRI cannot be performed, such as in cases when the person has a pacemaker or other metal implants in their body.
• CT scan helps to confirm the diagnosis, size, and the location of the prolactinoma.

Testosterone Level Blood Test

If the person is assigned male at birth and the clinical presentation is suspicious for prolactinoma, it is usually advised to check the level of testosterone in the blood. Low levels of testosterone confirm the diagnosis of prolactinoma.

Treatment for Prolactinoma

Treatment options for prolactinomas

• Pharmacotherapy (It is the preferred method of initial management)
• Surgery
• Radiation therapy

Medications

• Dopamine agonists: Control prolactin levels by shrinking the prolactinoma tumors.
• The most commonly used dopamine agonists are:
  • Cabergoline
  • Bromocriptine

• Cabergoline is the first-choice medication for treating prolactinomas. It has fewer side effects when compared to bromocriptine.
• Side effects of dopamine agonists include:
  • Nausea
  • Vomiting
  • Dizziness
• Relapse can be avoided only if the medications are continued for at least a period of 2 years.

Surgery

Surgery is done in case of the following conditions:

• If you have side effects to medications that are prescribed to treat prolactinomas.
• If you are taking antipsychotic medication which interacts with the medications taken for prolactinoma treatment.
• If the medications are not working and fail to reduce the size of the tumor.
• If the prolactinoma is large in size and you are trying to get pregnant in the recent future.

Two types of surgeries are carried out to treat prolactinoma:

• Transsphenoidal surgery: Is the most common surgery to treat prolactinomas and is performed through an incision made at the back of the nasal cavity or under the upper lip.
• Transcranial surgery: Is done when the size of the prolactinoma is large and has spread to other areas. The surgery is performed by opening the skull.

Risks associated with surgical removal of prolactinomas:

• Impaired pituitary function (hypopituitarism)
• Temporary diabetes insipidus
• Cerebrospinal fluid leak
• Infection

Radiation Therapy

• It is not the common option when it comes to management of prolactinomas.
• It is only performed when both surgery and medications fail in treating the condition.
• The number of radiation doses prescribed depends upon:
  • Size of the tumor
  • Location of the tumor
• Side effects associated with radiation therapy include:
  • Vision loss (which is a rare side effect)
  • Low levels of thyroid hormone (Most common side effect)
  • Brain injury (rare side effect)
  • Decrease in the level of other hormones secreted by the pituitary gland.

Prognosis

• The prognosis for prolactinomas is generally very good.
• Dopamine agonists usually work for four out of five people.
• When it comes to surgery, it is successful in most cases.
• Surgery successfully corrects prolactin levels in 90% of people with small prolactinomas and 50% with large prolactinomas.
  • Larger prolactinomas cannot be fully removed using surgery, and with the help of medication, prolactin levels can be brought back to normal range post-surgery.

Points to Remember

• At one time, oral contraceptives were falsely believed to contribute to the development of prolactinomas.
• Stress is also considered an important contributor of hyperprolactinemia, and its clinical significance is still being explored.
• In young individuals, prolactinomas are the most common type of pituitary adenoma overall (Especially in adolescents older than 12 years of age).

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