Prolactin: definition and meaning
Prolactin is a hormone made by the pituitary gland that stimulates breast milk production after birth. It rises during pregnancy and breastfeeding, and stays low otherwise. High prolactin outside pregnancy, called hyperprolactinemia, can suppress ovulation and cause irregular or missing periods, breast discharge and difficulty conceiving.
Why prolactin affects your cycle
Prolactin dampens the release of GnRH from the hypothalamus, which lowers FSH and LH. Without those signals, follicles don't mature and ovulation may stop. That's why breastfeeding often delays periods, and why high prolactin can cause secondary amenorrhea or oligomenorrhea.
Causes of high prolactin
- Pregnancy and breastfeeding (normal)
- A small, usually benign pituitary growth called a prolactinoma
- Some medicines, including certain antipsychotics, anti-sickness drugs and some antidepressants
- An underactive thyroid
- Stress, recent exercise or nipple stimulation, which can raise a single reading
Signs and testing
- Irregular or absent periods
- Milky discharge from the nipples when not breastfeeding
- Difficulty getting pregnant, lower libido, vaginal dryness
- Headaches or vision changes, with larger pituitary growths
A simple blood test measures prolactin, ideally in the morning and at rest. If it's high, doctors repeat it and may check thyroid function and order an MRI. Medicines called dopamine agonists usually bring prolactin down and restore periods.
Prolactin also interacts with mood and stress hormones, and low libido or low mood are reported with high levels. See period while breastfeeding for the normal rise after birth.
Frequently asked questions
Can stress raise prolactin?
Yes, slightly and temporarily. That's why a borderline result is usually repeated.
Does high prolactin cause infertility?
It can, by stopping ovulation. Treatment usually restores ovulation and fertility.
Why don't I get periods while breastfeeding?
Frequent feeding keeps prolactin high, which holds back the brain signals for ovulation. As feeds space out, prolactin falls and periods usually return, sometimes before weaning is complete.
Sources
This page is for information only and isn’t medical advice. If something worries you, please talk to a doctor.
Keep reading
Periods while breastfeeding: when they return and what changesYour period while breastfeeding: why it's delayed, when it usually comes back, whether it affects your milk, pregnancy before it returns, and red flags.
What is secondary amenorrhea?Secondary amenorrhea means your periods stop for 3 months or more after you've had them before. Common causes, tests, and when to see a doctor.
What is the hypothalamus?The hypothalamus is the brain area that starts the hormone chain behind your menstrual cycle. What it does, why stress can delay periods, and hot flashes.
Why did my period stop?Why did my period stop? Pregnancy first, then stress, weight change, exercise, PCOS, thyroid, birth control or perimenopause. What to check and when.Infertility: definition and meaningInfertility means not getting pregnant after 12 months of regular unprotected sex, or 6 months if you're 35 or older. Causes, tests and next steps.