Prolactin

Single-chain peptide hormone (198 amino acids) produced in the lactotropic cells of the anterior pituitary gland. Prolactin is also produced in peripheral blood cells. Prolactin circulates in various blood cells. forms. In normal sera, prolactin is present in 85-95% as monomeric prolactin with a molecular mass of 23kD. 10% is accounted for by the 50 kDa "big-prolactin" or the macro-prolactin (150- to 170-kDa "big-big-prolactin"). These are biologically inactive macrocomplexes that form after the secretion of the monomeric prolactin.

Prolactin acts on the mammary gland and controls milk production in women after pregnancy by stimulating lactogenesis and galactopoiesis. Structurally, prolactin is similar to growth hormone and human placental lactogen. Prolactin plays an important role in the innate and adaptive immune response. Elevated prolactin levels have been described in autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis, Sjögren's syndrome and systemic scleroderma (Jara LJ et al. 2011).

Prolactin (PRL) is inhibited by the Prolactin Inhibiting Factor (PIF), which is produced in the hypothalamus. This is identical to dopamine. Entpsrehend, dopamine antagonists lead to an increase in the prolactin concentration. Furthermore, there is a prolactin-releasing factor whose structure has not yet been fully elucidated. TRH also leads to a stimulation of prolactin secretion.

Prolactin shows fluctuations in the course of the day and is released pulsatile. At night, secretion is increased (increase of 60-80% during the late sleep phases).

Standard value: The reference range for women is between 4.8 - 23.3 µg/l, for men between 4.0 - 15.2 µg/l

Pathologically increased: prolactinoma, renal insufficiency, hypothyroidism, medication, disturbed dopamine transport.

• Increases in serum prolactin concentration (hyperprolactinaemia) are usually caused by medication or functional impairment of other organs, particularly the kidneys.
• More rarely, prolactin-secreting pituitary adenomas are the cause (prolactinoma see pituitary diseases, skin changes).

• Diseases and conditions that can lead to hyperprolactinaemia:
  • hypo- and hyperthyreosis
  • Restricted kidney function
  • Stress (mental and physical).
• Drugs that can lead to hyperprolactinemia:
  • angiotensin II
  • Antiandrogens (Cyproterone acetate)
  • Antidepressants (Amitryptiline, Clomipramine, Desipramine, Dopexin, Imipramine, Maprotiline and others)
  • Antiemetics (domperidone, metoclopramide)
  • Antihypertensives (Clonidine, Methyldopa, Reserpine)
  • H2-receptor blockers (cimetidine, ranitidine)
  • Melatonin
  • Neuroleptics of the benzisoxazole piperidine group
  • Neuroleptics of the butyrophenone group
  • Neuroleptics of the dibenzodiazepine group
  • Neuroleptics of the phenothiazine group (chlorpromazine, levomepromazine, fluphenazine, perphenazine)
  • Neuroleptics of the group of thioxanthenes (chlorprothixes, zuclopenthixol, flupentixol)
  • Opioids
  • Opiates, cocaine
  • MAO inhibitors
  • Serotonin reuptake inhibitors (fluoxetine)
  • Antiemetics (metoclopramide, domperidone)
  • Calcium antagonists (e.g. verapamil)
  • Antihypertensives (reserpine, alpha-methyldopa)
  • protease inhibitors (?).

• Required material: Blood serum.
• Note: The blood sample should be taken about 4 hours after getting up
• Before taking the blood sample, drugs that can lead to hyperprolactinemia should be discontinued, if possible 1 week before.
• Prolactin serum concentrations above 200 ng/ml (with a reference range up to about 20 ng/ml) indicate with a very high probability the presence of a prolactin-producing anterior pituitary adenoma; values between 20 and 80 ng/ml are usually caused by medication.
• Dynamic tests are not suitable for differentiating between functional and tumor hyperprolactinemia. As an imaging method, an MRI of the sella region is indicated in suspected cases of prolactin-secreting pituitary adenoma.
• Any hyperprolactinemic sample without corresponding symptoms should be examined for the presence of macroprolactin.

1. Cabrera-Reyes EA et al (2017) Prolactin function and putative expression in the brain. Endocrine 57:199-213.
2. Chahal J et al (2008) Hyperprolactinemia. Pituitary 11:141-146
3. Jara LJ et al (2011) Prolactin and autoimmunity. Clin Rev Allergy Immunol 40:50-59.
4. Lopez Vicchi F et al. (2017) Prolactin: The Bright and the Dark Side. Endocrinology 158:1556-1559.

Standard values (ug/l):

Old value (w) Value (m)

Day 5 102-496 102-496

2nd-12th month 5.3-63.3 5.3-63.3

12-13-LJ 2.5-16.9 2.8-16.1

Adults 3.8-23.2 3.0-14.7