II. Physiology
- Prolactin is a Protein synthesized and secreted by Lactotrophs (acidophil cells) in the anterior pituitary
- Stimulation (releasing factors)
- Vasoactive intestinal polypeptide (VIP)
- Thyroid Releasing Hormone (TRH, short-term factor only)
- Estrogen
- Postulated, specific Prolactin releasing Hormone (as of 2022, not identified)
- Inhibition
- Hypothalamic Dopamine (Prolactin Inhibiting Factor or PIF)
- Stimulation (releasing factors)
- Prolactin Characteristics
- Polypeptide Hormone with 198 Amino Acids
- Resembles Human Growth Hormone (hGH)
- Resembles Human Placental lactogen (hPL)
- Prolactin Effects
- Prolactin stimulates milk secretion into the Breast alveoli in pregnancy and Lactation
- Oxytocin stimulates myoepithelial cells to contract, expressing Breast Milk from the nipple
- Prolactin response assumes prior Breast development
- Breast ducts, fat and stroma develop with Estrogen exposure
- Breast glands, alveoli and secretory tissues develop with Progesterone exposure
- 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
III. Pathophysiology
IV. Technique: Preparation for lab draw
V. 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
- Initially (<3 months postpartum)
- References
- Bakerman (1984) ABCs of Lab Data, p. 342