Puerperal breast feeding does not stimulate circulating opioids in humans

Area of Science:

• Reproductive Endocrinology
• Neuroendocrinology
• Lactational Physiology

Background:

• Postpartum hormone dynamics are crucial for maternal adaptation.
• Proopiocortin (POMC)-related peptides and prolactin (PRL) play key roles in lactation and stress response.
• Serotoninergic pathways are implicated in both PRL release and POMC peptide regulation.

Purpose of the Study:

• To investigate the changes in ACTH, beta-lipotropin (beta-LPH), beta-endorphin (beta-EP), PRL, and cortisol during early puerperium.
• To assess the hormonal response to suckling in healthy lactating women.
• To explore the neuroendocrine mechanisms underlying PRL release and POMC peptide secretion during breastfeeding.

Main Methods:

• Hormone levels (ACTH, beta-LPH, beta-EP, PRL, Cortisol) were measured in 7 healthy lactating women.
• Measurements were taken on days 1-5 postpartum, at 9:00 AM, before and 30 minutes after suckling.
• Analysis focused on hormonal changes from delivery levels and responses to suckling stimulation.

Main Results:

• ACTH, beta-LPH, beta-EP, and cortisol levels decreased significantly from delivery, stabilizing by day 2 postpartum.
• Plasma PRL levels declined but remained elevated, with suckling stimulating a further increase.
• Suckling did not alter ACTH, beta-LPH, beta-EP, or cortisol levels, suggesting a lack of stress response.

Conclusions:

• Early postpartum hormone profiles show a rapid normalization of POMC-related peptides and cortisol.
• Breastfeeding is not a stressful event, as evidenced by the absence of a typical POMC peptide stress response.
• PRL release during suckling is mediated by serotoninergic neurons distinct from those controlling POMC peptide secretion.