How are prolactin levels interpreted in a breastfeeding woman?

Interpretation of Prolactin Levels During Breastfeeding

Prolactin levels in breastfeeding women remain elevated above normal non-lactating levels and should be interpreted with consideration of this physiological state rather than using standard reference ranges. 1

Normal Prolactin Patterns During Breastfeeding

• Prolactin levels increase significantly during pregnancy, reaching 10-20 times normal levels by the end of gestation 2
• After delivery, prolactin levels decrease but remain elevated above non-lactating levels while breastfeeding continues 3
• Prolactin levels show diurnal variation during lactation, with highest concentrations between 2:00-6:00 AM and lowest between 10:00 AM-6:00 PM 4
• Prolactin concentration in milk is higher in the morning hours, with the greatest difference between fore-milk and hind-milk occurring between 6:00-10:00 AM 4

Factors Affecting Prolactin Levels During Breastfeeding

• Nursing frequency directly impacts prolactin levels - more frequent nursing maintains higher prolactin levels for longer periods (up to 13 months postpartum) 3
• Early postpartum (first two months), nursing episodes typically trigger acute prolactin surges 3
• After 6 months postpartum, the prolactin surge response to nursing becomes less consistent 3
• Women with insufficient milk production tend to have higher prolactin levels compared to those with sufficient milk production 5
• Post-lactational prolactin levels are significantly influenced by the duration of breastfeeding the first child, not simply by pregnancy or subsequent children 5

Clinical Significance of Prolactin Levels During Breastfeeding

• Elevated prolactin is physiologically normal during lactation and should not be misinterpreted as pathological hyperprolactinemia 1
• When measuring prolactin in breastfeeding women, timing relative to nursing episodes and time of day should be considered 4, 3
• If concerned about truly pathological hyperprolactinemia in a breastfeeding woman, consider:
  • Symptoms inconsistent with normal lactation
  • Prolactin levels markedly higher than expected for lactation stage
  • Presence of visual field disturbances or other mass effect symptoms 6

Special Considerations

• Some medications can affect prolactin levels and milk production during breastfeeding:
  • Clonidine may reduce prolactin secretion and potentially reduce milk production in early postpartum period 7
  • Bromocriptine, a dopamine agonist used to treat hyperprolactinemia, suppresses lactation and should be avoided in women who wish to breastfeed 6
• Ceasing lactation can reduce prolactin levels and may be considered in specific clinical scenarios:
  • In women with hereditary angioedema, lactation might increase edematous attacks due to elevated prolactin levels 7
  • Ceasing lactation might reduce attack frequency by decreasing serum prolactin levels in these patients 7

Pitfalls to Avoid

• Don't interpret prolactin levels in breastfeeding women using standard reference ranges for non-lactating individuals 1
• Don't overlook macroprolactinemia (high molecular weight prolactin aggregates) as a potential cause of elevated prolactin measurements 6
• Don't forget to consider medication effects on prolactin levels when interpreting results 6
• Don't assume that all elevated prolactin levels in breastfeeding women require treatment or indicate pathology 1, 3