Prolactin (PRL)

Prolactin (PRL, synonyms: prolactin; lactotropic hormone (LTH); lactotropin) is a hormone from the anterior pituitary (pituitary gland) that acts on the mammary gland and controls milk production in women after pregnancy. Prolactin itself is inhibited by Prolactin Inhibiting Factor (PIF), which is produced in the hypothalamus. This is identical to dopamine. Prolactin shows fluctuations during the day and is secreted in a pulsatile manner. At night, the secretion is increased (increase of 60-80% during the late stages of sleep). A secretory stimulus (release stimulus) is provided by:

Have an inhibitory secretory effect:

The procedure

Material needed

  • Blood serum

Preparation of the patient

  • Blood collection should be performed circa 4 hours after getting out of bed
  • Prior to blood sampling, medications that can lead to hyperprolactinemia should be discontinued, if possible, one week beforehand – see “Further notes” for more information.

Interfering factors

  • Acute stressful situations
  • Blood collection at very early times of the day during the winter months
  • Breast stimulation in advance
  • See under preparation of the patient

Normal values children

Age Normal values in μg/l
5th day of life (LT) 102-496
2-12 months of age (LM) 5,3-63,3
2nd-3rd year of life (LY) 4,4-29,7
4th-11th year of life 2,6-21,0

Normal values girls/women

Age Normal values in μg/l
12-13 LJ 2,5-16,9
14-18 LJ 4,2-39,0
> 18. LJ 3,8-23,2
Pregnancy,1st trimester (third trimester). < 75,0
Pregnancy,2nd trimester < 150
Pregnancy,3rd trimester < 300
Postmenopausal < 16,0

Normal values boys/men

Age Normal values in c
12-13 LJ 2,8-24,0
14-18 LY 2,8-16,1
> 18. LJ 3,0-14,7

Conversion factor: 1 μg/l = 24 mIU/ml

Indications

Women

  • Galactorrhea (abnormal breast milk discharge) – unilateral or bilateral.
  • Mastodynia (cycle-dependent tightness in the breasts or breast pain).
  • Cycle disorders (oligomenorrhea, corpus luteum insufficiency, anovulation, amenorrhea).
  • Acne (eg, acne vulgaris)
  • Hirsutism (male type of hair)
  • Libido disorders
  • PCO syndrome (polycystic ovary syndrome; symptom complex characterized by hormonal dysfunction of the ovaries).
  • Suspicion of prolactinoma

Men

  • Hypogonadism (hypofunction of the gonads)
  • Galactorrhea
  • Gynecomastia (breast formation of the male)
  • Libido and potency disorders

Interpretation

Interpretation of increased values

  • Prolactinoma (prolatin level usually > 40 ng/ml) – prolactin-producing tumor located in the pituitary gland (pituitary gland).
  • Deficiency of prolactin inhibitory factor (PIF) = dopamine.
  • Pituitary tumors leading to a deficiency of prolactin inhibiting factor (PIF).
  • Injuries to the pituitary gland such as transection of the pituitary stalk.
  • Functional hyperprolactinemia (prolactin level < 40 ng/ml).
    • No evidence of pituitary tumor
    • Mental stress
    • Stress
    • Gravidity (pregnancy)
    • Lactation phase (breastfeeding phase)
  • Higher renal insufficiency (renal dysfunction; prolactin is decreased renally excreted and accumulated).
  • Hypothyroidism (hypothyroidism) or latent (subclinical) hypothyroidism – prolactin levels rarely > 40 ng/ml.
  • Physical or mental stress
  • Medications that may induce hyperprolactinemia (dopamine antagonists: see under “Additional Information”).

Interpretation of decreased values

  • Pituitary insufficiency (hypopituitarism).
  • Medications used to treat hyperprolactinemia (dopamine agonists: bromocriptine; lisuride; pramipexole; ropinirole)
  • Menopause

Other notes

  • Levels above 200 ng/ml (= μg/L) are almost always probative of prolactinoma; elevated prolactin levels up to 200 ng/ml may be due to microadenoma, among other causes.
  • Prolactin levels in the high-normal and low hyperprolactinemic ranges are reported to be associated with metabolic health: The beneficial effects of PRL occur at high levels within normal circulating levels and above the conventional hyperprolactinemia threshold (25 μg/l). In contrast, low levels of PRL are associated with metabolic disease.

The agents or groups of agents listed below can induce hyperprolactinemia, leading to follicle maturation disorders (disruption of oocyte maturation) in women and libido and potency disorders in men: