Lab

Prolactin

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Prolactin, Serum Prolactin

  • Physiology
  1. Prolactin is synthesized and secreted by Lactotrophs in the anterior pituitary
    1. Stimulation (releasing factors)
      1. Vasoactive intestinal polypeptide (VIP)
      2. Thyroid Releasing Hormone (TRH, short-term factor only)
      3. Estrogen
    2. Inhibition
      1. Hypothalamic Dopamine (Prolactin Inhibiting Factor or PIF)
  2. Prolactin Characteristics
    1. Polypeptide hormone with 198 amino acids
    2. Resembles Human Growth Hormone (hCG)
    3. Resembles Human Placental lactogen (hPL)
  3. Prolactin increases with infant Breast Feeding
    1. Increases with each Breast Feeding episode
    2. Prolactin levels gradually level off after the first few months of regularly Breast Feeding
    3. Prolactin decreases to normal within 1-2 months of stopping Breast Feeding
  • Preparation
  1. Fasting level drawn before noon
  2. No Breast stimulation in last 48 hours
  • Interpretation
  • Normal Levels
  1. Adult: <20 ng/ml
  2. Newborn: 100 to 300 (falls below 20 after 6 weeks)
  3. Pregnancy
    1. First Trimester: <80 ng/ml
    2. Second trimester: <160 ng/ml
    3. Third Trimester: <400 ng/ml
  4. Lactation
    1. Initially (<3 months postpartum)
      1. First week: 100 ng/ml basal level
      2. First 1-2 months: 50 ng/ml basal level
      3. Suckling raises Prolactin 10-20 fold above basal
    2. Later (3-6 months postpartum)
      1. Basal rates approach non-pregnant levels
      2. Suckling may double basal level
  5. References
    1. Bakerman (1984) ABCs of Lab Data, p. 342
  • Interpretation
  • Increased Prolactin > 20 ng/ml