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Prolactin Levels and Fertility
A blog by Dr. Daniel Kort, Damien Fertility Partners, December 29, 2014
Prolactin is a hormone produced in the pituitary gland, the “master gland” of the brain. Prolactin has multiple actions in the body, mostly involving pregnancy and breast milk production for a newborn baby. However, prolactin can be elevated when a woman is not pregnant or breastfeeding, causing a variety of conditions that impact a woman’s normal menstrual function and fertility potential.
Patients are diagnosed with elevated prolactin levels (“hyperprolactinemia”) from simple blood tests that measure the amount of prolactin in the blood. Depending on the laboratory used, prolactin levels in non-pregnant women above 20-25 (ng/ml) are considered elevated. However, as there are daily variations in prolactin levels in the blood, it may be necessary to repeat the test if prolactin levels are only slightly elevated.
Many women receive this diagnosis after evaluation for infertility or irregular periods, but many others have no symptoms at all. While patients will occasionally present with spontaneous milky nipple discharge (“galactorrhea”), the majority do not have this symptom.
Mild increases in prolactin levels between 20-50 (ng/ml) typically do not cause noticeable changes in menstrual cycles, but may decrease overall fertility. Prolactin levels between 50-100 (ng/ml) typically cause irregular menstrual periods and significantly decrease a couple’s fertility. Prolactin levels over 100 (ng/mL) can drastically alter the normal function of a woman’s reproductive system, causing symptoms of menopause (no menstrual periods, hot flashes, vaginal dryness) and infertility.
Causes of Hyperprolactinemia
There are many different conditions that cause elevations in prolactin levels. Normal elevations in prolactin levels occur in pregnancy, in response to nipple stimulation (usually after delivery of the newborn), and in times of stress. Abnormal elevations in prolactin levels occur when prolactin producing cells inside the pituitary (lactotrophs) produce more prolactin than required or when lactotrophs grow abnormally to form tumors (prolactinomas). In addition, elevations in prolactin levels can occur as a side-effect of certain psychiatric medications.
If a prolactin secreting tumor is suspected, patients will undergo imaging of the brain, typically using MRI. If a tumor is found on brain imaging, they are classified by size:
- tumors less than 1 centimeter are classified to as microadenomas
- tumors greater than 1 centimeter are classified as macroadenomas
Macroadenomas can cause neurologic symptoms, usually changes in vision, and require immediate attention and treatment. Patients are typically referred to a neurologist for specialized visual testing. During pregnancy, patients with a macroadenoma must be followed closely with regular examinations and monitoring of prolactin levels, as these tumors are more likely to grow to dangerous sizes. Typically, additional treatment is required (see below).
Both microadenomas and macroadenomas are typically NOT cancerous and can be treated without surgery (see below). These tumors are monitored clinically with regular prolactin levels and repeat brain imaging when necessary.
Treatment for Hyperprolactinemia:
The majority of patients who have elevated prolactin can be treated successfully with a variety of medications. These medications mimic the actions of the brain chemical dopamine (dopamine agonist), which limit the production of prolactin from the pituitary and cause the cells that produce prolactin (lactotrophs) to regress. Currently, the two most common medications used are cabergoline (Dostinex®) and bromocriptine (Parlodel®). Side-effects of these medications include problems with blood pressure and mental “fogginess”, which can be minimized by starting with a small dose and gradually increases over time. Patients typically respond well to treatment and lower prolactin levels can be appreciated in 2-3 weeks. Medication dosages can be adjusted on an individual basis to maintain a normal prolactin level and are sometimes discontinued entirely. In a small minority of patients, medications are not effective in lowering prolactin levels and large tumors (macroadenomas) persist. In these cases, surgical treatment (transphenoidal adenoma resection) and/or radiation therapy can be performed.
Summary: Elevations in prolactin, a hormone secreted by the body with functions in pregnancy and breastfeeding, can negatively affect a woman’s reproductive function and fertility potential. Simple treatments, such a daily or weekly medications, are highly effective at reducing such elevations and may be necessary for women with this condition.