Prolactin: Low vs High Signs, Testing, Fertility, and Breast Health
Overview
Prolactin is a hormone made by the pituitary gland that plays a central role in breast development, milk production, and aspects of reproductive function. It is normally higher in pregnancy and breastfeeding and lower at other times. Clinicians usually think about prolactin when periods become irregular, fertility is reduced, breast discharge appears outside of breastfeeding, or there are symptoms that hint at a pituitary problem such as headaches or visual changes.
In many cases, prolactin is interpreted together with Thyroid-Stimulating Hormone, because low thyroid function can raise prolactin and change how results should be understood.
What Prolactin is and where it is made
Prolactin is a peptide hormone produced by the pituitary gland at the base of the brain.
Its release is mainly kept in check by dopamine from the hypothalamus, which acts as a brake. When this brake is reduced, prolactin can rise.
Levels increase naturally in pregnancy and breastfeeding to support breast changes and milk production.
What Prolactin does in your body
Supports breast development and preparation for lactation during pregnancy.
Stimulates milk production after childbirth when breastfeeding begins.
Influences reproductive hormones by interacting with the hypothalamic pituitary gonadal axis, which can affect ovulation and testosterone levels.
Can affect libido, menstrual regularity, and fertility when significantly outside the normal range.
May influence mood and sleep in some people, especially when very high.
When testing Prolactin makes sense
Menstrual irregularities, missed periods, or ovulation problems without a clear cause.
Difficulty conceiving when other common factors have been evaluated.
Breast discharge (galactorrhea) outside of pregnancy or breastfeeding.
Low libido, erectile issues, or low testosterone in men.
Headaches, visual changes, or other symptoms that raise concern about a pituitary lesion.
Monitoring of known prolactin related conditions or follow up after pituitary surgery or treatment.
Evaluation of side effects from medications known to raise prolactin.
How to think about high and low Prolactin results
This information is general and does not replace lab specific reference ranges or medical evaluation.
Low prolactin might be associated with:
Limited or delayed milk production after childbirth in some cases.
Pituitary underactivity when other pituitary hormones are also low.
Low prolactin alone is less common as a major clinical problem and is usually considered in the broader context of pituitary function.
High prolactin might be associated with:
Irregular or absent periods and lack of ovulation in women.
Breast discharge not related to pregnancy or breastfeeding.
Reduced libido and erectile issues in men, often with low testosterone.
Fertility problems in both women and men.
Headaches or vision changes when a prolactin producing pituitary tumor or other pituitary mass is present.
Possible contributors include prolactin secreting pituitary tumors, reduced dopamine signaling, low thyroid function, chronic kidney disease, chest wall stimulation or injury, and several medications such as some antipsychotics, antidepressants, and nausea treatments. A single high result is often confirmed with repeat testing, ideally under controlled conditions.
What can influence your Prolactin levels
Pregnancy and breastfeeding, where higher levels are expected.
Thyroid status, especially untreated hypothyroidism.
Medications that affect dopamine or serotonin pathways, including some antipsychotics, antidepressants, and anti nausea drugs.
Stress, poor sleep, and the timing of the blood draw, since acute stress and lack of rest can transiently raise prolactin.
Kidney function, with chronic kidney disease sometimes associated with elevated prolactin.
Pituitary and hypothalamic health, including benign tumors, prior surgery, or radiation.
Chest wall stimulation, injury, or irritation, which can occasionally affect prolactin signaling.
When to talk to a clinician about Prolactin
Prolactin results outside the reference range, especially when combined with cycle changes, breast discharge, or fertility concerns.
New or worsening headaches, visual changes, or other symptoms that suggest a pituitary issue.
Low libido or sexual dysfunction in men when testosterone is low and prolactin is high.
Difficulty establishing or maintaining milk supply after childbirth when guidance is needed.
Questions about whether a current medication could be driving prolactin changes and what alternatives exist.
A clinician can decide whether to repeat the test, adjust medications, check thyroid and other hormones, or arrange imaging of the pituitary if needed.
Prolactin in one view
Prolactin is a pituitary hormone that sits at the intersection of breast health, lactation, and reproductive function. High levels outside of pregnancy and breastfeeding can disrupt periods, lower libido, and affect fertility, while very low levels may point toward broader pituitary underactivity. Because thyroid status, medications, and stress can all shift prolactin, an out of range result is best interpreted in context, often alongside thyroid markers such as Thyroid-Stimulating Hormone and a careful medication review with a clinician.
