Prolactin and its control by dopamine !

Regulation
Exam priority: medium

Prolactin makes the breast produce milk. The brain keeps it switched off with dopamine; take the dopamine away and prolactin rises.

Updated 2026-11-01

Also called: PRL, Lactotrophs, Hyperprolactinemia

See it in 3D: Pituitary gland · Hypothalamus

What it is

Prolactin is a peptide from the lactotrophs of the anterior pituitary. Its main job is milk production after birth. Unlike the other pituitary hormones, it is held down all the time by dopamine from the hypothalamus. That is why anything that cuts the dopamine supply, from a stalk-compressing tumour to an antipsychotic, raises prolactin, and high prolactin in turn suppresses GnRH and fertility.

How it works, step by step

Tuberoinfundibular neurons in the arcuate nucleus release dopamine into the portal capillaries of the median eminence.
Dopamine binds D2 receptors on lactotrophs, lowers cAMP and blocks prolactin secretion and lactotroph growth.
Prolactin rises and reaches the hypothalamus, where it increases dopamine output: short-loop negative feedback.
In pregnancy, estrogen makes lactotrophs multiply, so prolactin climbs steadily; high estrogen and progesterone block milk until delivery.
After birth, suckling sends afferent signals that suppress dopamine and cause prolactin peaks with each feed.
High prolactin lowers GnRH pulse frequency (partly through kisspeptin neurons), so LH and FSH fall: lactational amenorrhea.

Hormone axes and feedback

Prolactin axisLesion None (normal)

Tap a box to see the hormone, or choose a lesion to see the lab pattern.

Stimulates (+)
Inhibits / negative feedback (−)
Level ↑
Level ↓

Prolactin axis. Choose the stalk lesion: unlike the other axes, prolactin goes up.

Reference values (vary by laboratory and assay)

Parameter	Value	Note
Prolactin, non-pregnant woman	≈ < 25 ng/mL	≈ < 530 mIU/L
Prolactin, man	≈ < 15–20 ng/mL
Prolactin, late pregnancy	can reach ≈ 200 ng/mL	physiological
Prolactinoma (macroadenoma)	often > 200 ng/mL	level tracks tumour size

Approximate values for a healthy adult at rest; each laboratory sets its own ranges.

Regulation

−Dopamine (D2): Tonic inhibition; the main control of the axis.
+Suckling and nipple stimulation: Reflex fall in dopamine and prolactin peaks.
+Estrogen (pregnancy): Lactotroph hyperplasia and higher prolactin.
+TRH: Stimulates lactotrophs: primary hypothyroidism can raise prolactin.
+Stress, sleep, exercise: Mild physiological rises (sample at rest).
−Prolactin itself: Increases hypothalamic dopamine (short loop).

Clinical notes

Antipsychotics and antiemetics that block D2 receptors cause galactorrhea and amenorrhea.
A non-secreting macroadenoma that compresses the stalk gives a moderate prolactin rise; this can be mistaken for a prolactinoma.
Very large tumours can give a falsely low result in some assays (hook effect); macroprolactin (a large, inactive complex) can give a falsely high one.
Sheehan syndrome (postpartum pituitary necrosis): the first sign is often failure to breastfeed because prolactin is lost.

Test yourself

Think of the answer, then tap the question to see it.

After traumatic section of the pituitary stalk, which anterior pituitary hormone rises, and why?

Prolactin. The other hormones lose their hypothalamic releasing factors and fall, but prolactin loses its inhibitor, dopamine, so it rises.

Why can primary hypothyroidism cause galactorrhea?

Low T4 removes feedback, so TRH rises. TRH stimulates lactotrophs as well as thyrotrophs, raising prolactin.

How does hyperprolactinemia cause amenorrhea?

Prolactin suppresses the pulsatile release of GnRH; LH and FSH fall, the follicles do not mature, estradiol falls and ovulation stops.

A man on a D2-blocking antipsychotic develops gynecomastia and low libido. What is the mechanism?

Blocking D2 on lactotrophs removes the dopamine brake; high prolactin lowers GnRH and testosterone, and the low androgen-to-estrogen balance favours breast tissue.

Add to my cards (4)

See it in 3D

The structures of Durgical's 3D anatomy where it happens.

In Biochemistry

← All of physiology

Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given.

Sources: 17.3 The Pituitary Gland and Hypothalamus (OpenStax (Rice University), 2022); Prolactinoma: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2025); Pituitary Adenoma (StatPearls (NCBI Bookshelf), 2024); Hall JE. Guyton and Hall Textbook of Medical Physiology, 13th ed. (ch. 76). Reference book used to check facts; its text and figures are not reproduced (Elsevier, 2016).

Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake

Representative model, for educational purposes only.