Talk About Breasts! Milk!

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Transcript

Oxytocin and Prolactin are two hormones that have very identical functions, while both hormones do have some exclusive functions, such as oxytocin stimulating the uterus contraction during labor childbirth, Oxytocin and Prolactin are both concerned with breast milk. Prolactin is responsible for the triggering the production of milk proteins, or breast milk, while oxytocin is responsible for activating “milk let down” when suckling. For the purpose of this recording, I will only be focusing on oxytocin and prolactin’s roles in breast-feeding. I’ll begin first by explaining prolactin’s qualities.

The most predominant structure of prolactin that is present in the human body is a single-chain polypeptide with 198 amino acids. Prolactin is mostly produced in the anterior pituitary gland, but also produced in breasts. The function of prolactin that I will be focusing on will be stimulating the mammary glands to produce milk; the other function of prolactin is sexual gratification after sexual acts, but I won’t be focusing on that. Prolactin is regulated by the dopaminergic system and levels of prolactin are proportional to the level of estrogen in females, and testosterones in males. In females, estrogen inhibits prolactins on its milk production; it is only the sudden drop of estrogen after child-birth that allows mothers to produce breast milk for their babies. When a baby starts suckling on his mother’s breasts, prolactin is secreted and released into circulation to bind to the mammary epithelial cell receptors in the mammary glands of the mother, which stimulates milk to be produced in a matter of few minutes. When a mother does not breast feed, prolactin levels will return to normal after 7 days, and cause her to stop producing milk, therefore, mothers will usually breast feed multiple times a day to stimulate prolactin production and produce a lot of milk.

Onto oxytocin…Oxytocin is a peptide of 9 amino acids produced in the posterior pituitary glands. Unlike prolactin, which produces milk when stimulated by a baby suckling, oxytocin is responsible for releasing milk from the breasts. When undergoing childbirth or breast feeding, oxytocin is produced and released to the receptors located in the myoepithelial cell of the mammary gland; this stimulates multiple actions. In labor, uterus contractions occur which allows a smoother childbirth, while in breastfeeding, oxytocin acts at the mammary glands allowing milk to be secreted from the nipples. Oxytocin levels also affect social behavior and some degree of sexual response.

Both oxytocin and prolactin are regulated in positive feedback, which is not too common in hormones. For example, during childbirth, when the baby is moving towards the vagina, pressure receptors within the cervix triggers the pituitary gland to produce oxytocin, which then binds to its receptors and cause uterus contraction. The same goes for the stimulation of prolactin and oxytocin production when a baby suckles during breastfeeding. The chemical pathways of both prolactin and oxytocin are neuroendocrines, since they undergo endocrine secretion and are triggered by nervous stimulation such as breastfeeding. Both hormones are lipid soluble hormones, since they belong to the endocrine system and diffuse into a cell to bind with receptors.

And that about concludes my talk about where breast milk comes from!