Lecture 29.5: Lactation

Hormones during breastfeeding

Estrogen stimulates prolactin secretion by anterior pituitary

Prolactin levels rise with nipple stimulation

Alveolar cells make milk in response to prolactin

High estrogen and progesterone down-regulate prolactin receptors in the breasts and inhibit the stimulatory effects of prolactin on milk production

What initiates lactation?

A drop in estrogen and progesterone after delivery

Breast development

Begins at puberty due to estrogen stimulation

Lactiferous ducts develop at puberty

Increases during pregnancy in response to progesterone and prolactin

Prolactin and hPL=full ductal and alveolar structure development

Breast size does not equal milk production

Oxytocin

Neuro peptide hormone with physiologic effects on childbirth, lactation, and social interactions

Synthesized in hypothalamus, transported and stored in posterior pituitary and released into blood

Milk ejection

Milk must be ejected from the alveoli into the ducts before the baby can obtain it

Regulated by positive feedback under stimulation of oxytocin

Suckling

Important to maintain milk production

Increases in nerve stimulation from nipples to hypothalamus = increased oxytocin and prolactin

Prolactins role in lactation

Milk production

Oxytocin’s role in lactation

Milk ejection, not production

Causes myoepithelial cells to contract the milk from alveoli into the ducts

The reflex release often becomes a conditioned response independent of baby suckling (lactation just from infant crying)

The benefits of breastfeeding

Good for both infants and mothers

Ideal nutrition for infants under 6 months

Contains maternal immunoglobulins

Lactose in human milk is 50% more than cow’s milk

Lactose is the main carbohydrate in breast milk and turns into glucose and galactose that can be absorbed by the baby

What do breastfed infants have a lower risk of?

Asthma

Obesity

T1D

Lower respiratory disease

Ear infections

SIDS

GI infections

NEC for preterm infants

What are the benefits to the mothers who are breastfeeding

Lowers maternal risk of breast and ovarian cancer

Facilitates mother-child bonding

Less postpartum bleeding