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