Milk secretion

• Prolactin secreted by anterior pituitary gland causes breast changes during lactation.
• Prolactin also stimulates the production of milk
• Estrogen increases secretion of prolactin and along with prolactin promotes breast growth and differentiation.
• Estrogen along with progesterone , estrogen antagonizes prolactin action on milk production and milk secretion
• Following parturition ,estrogen and progesterone concentration in plasma falls due to absence of placenta so milk production is increases due to effect of prolactin .
• Large secretory burst of prolactin occurs during each nursing period.
• This episodic burst of prolactin signals the breasts for maintenance of milk production .
• These prolactin pulse continue for several days after the mother completely stop nursing her infant .
• The mechanism mediating prolactin pulses is initiated by stimulation of nipple receptor by suckling that send afferent input to hypothalamus .
• This input inhibits hypothalamic release of dopamine .
• Decreased dopamine release from hypothalamus stimulates prolactin secretion.
• Prolactin also inhibit GnRH secretion from hypothalamus that prevent ovulation therefore , till mother continues to nurse the baby ,normally pregnancy does not occur.
• Suckling also stimulate milk ejection reflex.