Prolactin (PRL)

Sample

1. This is done on the serum of the patient.
2. The patient needs to be fasting for 12 hours.
3. Take the blood sample after 3 to 4 hours of the wake from sleep because:
   1. The level rises during the deep sleep.
   2. There is a peak in the early morning hours.
4. The sample may be stored at 4 °C for 24 hours.
5. For a long time can freeze the sample.
6. In case of borderline elevation of PRL:
   1. Repeat the estimation at least two times at some interval.
   2. Take the sample in the morning.
   3. Avoid excitement in the patient.
   4. Avoid breast stimulation and no trauma.
   5. No medication which can stimulate the PRL release like:
      1. Estrogen.
      2. Dopamine antagonists (metoclopramide, domperidone, haloperdol).
   6. Advise TSH in such cases where primary hypothyroidism, can elevate PRL.

Precautions

1. Take a sample in the morning between 8 to 10 AM after at least 3 to 4 hours of the wake.
2. It increases during sleep and peak level is in the early morning.
3. When collecting the sample, avoid emotional stress, exercise and protein ingestion, all of these increase the prolactin level.
4. In the case of the borderline raised level, advise estimation two more times and avoid breast stimulation, no trauma, and no interfering medication.

Indications

1. Diagnose prolactin-producing tumors, like pituitary adenoma.
2. Use to monitor the prolactin-producing tumors.
3. Used for secondary amenorrhoea or galactorrhea, infertility, and hyperprolactinemia.
4. Useful for the hypothalamic disease.
5. Monitor the effectiveness of surgery, chemotherapy, and radiation in prolactin-producing tumors.

Pathophysiology

1. The main function of Prolactin is to initiate and maintain the lactation.
   1. This is a lactogenic hormone synthesized by the pituitary gland.
   2. Prolactin induces ductal growth, develops lobular system and synthesis of milk production.
2. Prolactin is an anterior pituitary hormone for initiating and maintaining the lactation.
   1. It is 32 kD and is synthesized as preprolactin.

3. Prolactin release is stimulated by suckling and suppressed by stress.
4. Until puberty, both males and females have the same level.
5. Estrogen level gives rise to an increase in the prolactin level in females.
6. Prolactin secretion is controlled by the:
   1. prolactin-inhibiting hormone, which is dopamine.
   2. Prolactin-releasing factor (PRF), which is a thyrotropin-releasing hormone (TRH).
   3. Dopamine controls the prolactin secretion. When more dopamine then less prolactin.
   4. ACTH is increased with stress, leads to elevation of the PRL level.
   5. Last is the PRL feedback loop between the pituitary and hypothalamus.

 

7. During sleep prolactin level increase 2 to 3 times.
8. Prolactin has receptors on the target organs like the breast, adrenal glands, ovaries, testes, prostate, and liver.
9. Prolactin has various functions in the body and these are summarized as follows.

10. PRL like other hormones has a receptor on the cell membrane of target organs like breast, uterus, adrenal gland, testes, ovary, kidney, and liver.

12. Increased prolactin level is seen in :
    1. Breast stimulation.
    2. Pregnancy.
    3. Nursing.
    4. Stress.
    5. Exercise.
13. Pituitary tumors form acidophilic cells that produce prolactin.
14. The moderate level increase is seen in :
    1. Secondary amenorrhea.
    2. Galactorrhea.
    3. primary hypothyroidism.
    4. Polycystic ovary syndrome.
    5. Anorexia.

NORMAL

Source 1

Age	ng/mL
Coed blood	45 to 539
Newborn 1 to 7 days	30 to 495
Children Tanner stage	Male	Female
1	<10	3.6 to 12
2 to 3	<6.1	2.6 to 18
4 to 5	2.8 to 11.0	3.2 to 20
Adult
	3.0 to 14.7	3.8 to 23.2
		Pregnancy 3rd trimester= 95 to 473

• To convert into SI unit x 1.0 = µg/L
• Tanner stage is the physical scale of development of primary and secondary sex characteristics.

Source 2

• Adult male = 0 to 20 ng/mL
• Adult female = 0 to 25 ng/mL
• Pregnant female = 20 to 400 ng/mL

Source 4

Nonpregnant women	0 to 23 ng/mL
Pregnant women	34 to 386 ng/mL
Pregnancy 1st trimester	<80 ng/mL
Pregnancy 2nd trimester	<169 ng/mL
Pregnancy 3rd trimester	<400 ng/mL
Men	0 to 20 ng/mL
Children	3.2 to 20 ng/mL

Increased prolactin level is seen in:

1. Diseases of the hypothalamus and pituitary gland.
2. Prolactin-secreting pituitary tumors.
3. Acromegaly.
4. Galactorrhea and amenorrhea.
5. Paraneoplastic syndrome when there is Ectopic production from lung cancers, other tumors, and leukemia.
6. Hypothyroidism.
7. Polycystic ovary.
8. Anorexia nervosa.
9. Adrenal insufficiency.
10. Metastatic cancer of the pituitary gland.
11. Chronic Renal failure.

Decreased Prolactin level is seen in:

1. Sheehan’s syndrome (after delivery may have hemorrhage or infarction of the pituitary gland).
2. Pituitary destruction by the tumors e.g. Craniopharyngioma.

Hyperprolactinemia leads to in:

• Females
  1. Anovulation With or without irregularity in menstruation.
  2. Galactorrhea and amenorrhea.
  3. Or galactorrhea alone.
• In Males
  1. Oligospermia
  2. May have impotence.
  3. Or both.
  4. Men with PRL secreting pituitary adenoma mostly have a presentation of macroadenoma and visual disturbance because of large tumor size pressing on the optic chiasma.
  5. 30% of the microadenoma patients have a clinically silent tumor. But the PRL level will be raised.
• Imaging like CT or MRI is advised.
• Patients with >150 ng/mL have PRL secreting tumors.
  • Many patients have >1000 ng/mL of PRL.
  • PRL level >200 ng/mL is enough evidence for PRL-secreting pituitary tumors.

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