Prolactin

Role of Prolactin in the Body

Prolactin is a hormone produced by the pituitary gland, playing a key role in the reproductive system and beyond.

Main Functions:

1. Lactation – stimulates milk production after childbirth.
2. Reproductive health:

• In women: influences the menstrual cycle, ovulation, and fertility.
• In men: involved in testosterone synthesis and spermatogenesis.

1. Immune regulation – modulates immune cell function.
2. Fluid and electrolyte balance – affects the kidneys (fluid retention).
3. Stress response – prolactin levels rise under stress, anxiety, and physical exertion.

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Symptoms of Prolactin Deficiency (Hypoprolactinemia)

Causes:

• Hypopituitarism (pituitary insufficiency due to trauma, surgery, or tumors).
• Use of dopaminergic drugs (levodopa, bromocriptine).

Symptoms:

• In women:
• Inability to breastfeed (lack of milk after childbirth).
• Menstrual irregularities (infrequent periods or amenorrhea).
• In men:
• Reduced libido, infertility (rare).
• General:
• Dry mucous membranes (due to reduced effect on fluid balance).

Important: Prolactin deficiency is rare and usually associated with generalized pituitary dysfunction.

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Symptoms of Prolactin Excess (Hyperprolactinemia)

Causes:

• Prolactinoma (benign pituitary tumor).
• Hypothyroidism (elevated TSH stimulates prolactin).
• Medication use (antidepressants, antipsychotics, antiemetics).
• Chronic stress, nipple stimulation, kidney failure.

Symptoms:

• In women:
• Galactorrhea (milk production outside of pregnancy and lactation).
• Menstrual irregularities (oligomenorrhea, amenorrhea).
• Infertility (due to suppressed ovulation).
• Reduced libido, vaginal dryness.
• In men:
• Gynecomastia (breast enlargement).
• Erectile dysfunction, reduced libido.
• Infertility (oligospermia).
• General:
• Headaches, visual disturbances (with macroadenoma).
• Osteoporosis (with prolonged elevation).

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Normal Prolactin Levels in Blood Tests

Levels depend on sex, age, and the laboratory.

Reference Values (µIU/L or ng/mL)*:

Group	Women (non-pregnant)	Men
Basal Level	60–500 µIU/L (3–25 ng/mL)	60–400 µIU/L (3–20 ng/mL)
Pregnant Women	Up to 10,000 µIU/L (500 ng/mL)	—
Postmenopausal	25–400 µIU/L (1–20 ng/mL)	—

*Conversion: 1 ng/mL ≈ 21 µIU/L

Important Notes:

• Prolactin is secreted in pulses, peaking at night and in the morning.
• The test should be taken on an empty stomach, in the morning, 2–3 hours after waking.
• Avoid before testing:
• Stress and physical exertion.
• Nipple stimulation, sexual activity.

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What to Do if Levels Are Abnormal

If Prolactin is Elevated:

1. Repeat the test (rule out stress or physical exertion).
2. Rule out hypothyroidism (TSH, free T4).
3. MRI of the pituitary gland (if prolactinoma is suspected).
4. Treatment:

• Dopamine agonists (bromocriptine, cabergoline).
• Surgery (for macroadenomas).

If Prolactin is Low:

1. Check other pituitary hormones (TSH, LH, FSH, cortisol).
2. MRI of the pituitary gland (if hypopituitarism is suspected).
3. Replacement therapy (if other hormone deficiencies are present).

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Conclusion

• Prolactin is a key hormone for lactation, reproduction, and stress adaptation.
• Excess causes infertility, galactorrhea, and reduced libido.
• Deficiency is rare but dangerous, leading to lack of lactation and hormonal imbalance.
• Normal range:
• Women: 60–500 µIU/L (3–25 ng/mL).
• Men: 60–400 µIU/L (3–20 ng/mL).