Hormones and Breastfeeding

There is a very tight interaction between women’s health, hormonal influence, pregnancy, and breastfeeding. Also, breastfeeding is a practice that has ties to community culture and family, both important contributors to women’s health. Nevertheless, breastmilk is essential for infant nutrition and should be exclusive for the first 6 months, as recommended by the CDC, AAP, ACOG, and many other major health organizations. Indeed, hormones and breastfeeding’s physiology plays a determining factor in breast function, babies’ nutrition, and the dyad interaction.


Breast development:


There is no glandular organ that is everchanging like the breast tissue since the transformation starts in the 20-day-old embryo with milk lines proliferation and will eventually develop into mammary ridges.  Later, at week 6, the areola and nipple start to form in the same way the milk ducts are developing. The process will remain inactive until puberty, when the breast bud development is influenced by estrogen, progesterone, corticosteroids, and thyroxine. These hormones will also influence the growth of alveolar buds and milk ducts with every new menstruation cycle.


Lactation physiology:


Lactogenesis I
 15–20 weeks of gestation. This stage is hormonally driven. All women will be able to synthesize milk components. Colostrum production begins midway through the pregnancy.

§  Initiation of milk synthesis from mid-pregnancy to late pregnancy.

§  Differentiation of alveolar cells into secretory cells.

§  Prolactin stimulates mammary secretory epithelial cells to produce milk.

Lactogenesis II
 30–40 hours after birth. It is initiated by the birth of an infant plus removal of the placenta. For lactogenesis II to begin, progesterone levels have to drop dramatically to allow prolactin and other hormones like insulin, thyroxin, cortisol, and oxytocin to take action. Women feel increased breast fullness during this stage, which commonly lasts 30-40 hours after birth.

§  Closure of tight junctions in the alveolar cell.

§  Triggered by the rapid drop in the mother’s progesterone levels.

§  Onset of copious secretion of milk.

§  Fullness and warmth in breasts.

§  Switch from endocrine to autocrine control.


Lactogenesis III
 (Galactopoesis) This stage will only continue if milk production is driven in the individual.  A steady stimulation, supply, and removal of breastmilk are the factors that keep this stage going, and it is not driven by autocrine control.

§  Maintenance of established secretion and breastfeeding.

§  Control by the autocrine system (supply-demand).

§  Breast size decreases between 6 and 9 months postpartum.


An additional stage has been suggested previously, and it is called involution. Involution is present after 40 days after the last breastfeeding. Eventually, in this stage, the milk-producing epithelial cells are removed; they are 2 steps to this process.

1.     Death of secretory epithelium.

2.     Replacement of milk-producing epithelial cells with adipocytes.

Maternal conditions impacting breastfeeding:
Primiparity Maternal age +30
Cesarean birth Long stage II of labor
Maternal fluid overload obesity/BMI
PCOS Diabetes type I or II
Analgesia on labor Placental retention
Stress Breast surgery (in some cases)


Hormones involved in breastfeeding:

Prolactin Growth: nipple, breast mass, and areola.

Released by the anterior pituitary gland by angiotensin II, gonadotropin-releasing hormone (GnRH), and vasopressin.

Levels of prolactin rise when there are nipple stimulation and breast emptying.

Initiates and maintains milk production, and it works along with oxytocin.

§  Prolactin follows a circadian rhythm; its levels are higher in the day.

§  Since levels rise with suckling stimulation, and they can remain high even if a mother breastfeeds for years.

§  High levels of prolactin induce ovulation delay, inhibiting follicle-stimulating hormone.

§  Smoking is associated with low levels of prolactin.

§  Depression is linked to low serum prolactin levels.

§  Present in breastmilk.

§  Suckling stimulation increases the development of prolactin receptors at the mammary gland.

Cortisol This hormone works synergistically with prolactin to stimulate milk production in the mammary system. The presence of prolactin and the interaction between insulin and cortisol allows cell differentiation of epithelial cells into mature milk cells.

Corticoids secreted by the adrenal glands regulate water transport across cell membranes during lactation.

High cortisol levels are linked to a delay in lactogenesis.

Progesterone Growth: lobes, lobules, alveoli.

Required to maintain pregnancy and interferes with prolactin action at the alveolar cell receptor level. It reduces its action and levels when the placenta is removed.

Inhibition of lactation and milk secretion.

Prolactin-inhibiting factor PIF is secreted by the hypothalamus and is believed to be mediated by dopamine. Dopamine itself inhibits prolactin secretion.

§  Milk removal and nipple stimulation inhibit PIF and dopamine secretion.

Oxytocin (stimulated by suckling) The posterior pituitary gland releases oxytocin with suckling.

§  Causes milk-ejection reflex, commonly called letdown.

§  Contracts the myoepithelial cells that surround the alveoli, resulting in milk removal from the breast.

§  It is released in pulsatile waves and carried through the bloodstream to the breasts.

§  Oxytocin serum levels rise within 1 minute of nipple stimulation.

§  Oxytocin influence is associated with calmness in mothers and reported sedation and lower corticosteroid levels in rats.

§  Oxytocin is reversely associated with ACTH, cortisol, glucose, and norepinephrine.

The impact that endocrine hormones have on lactation and breastfeeding is remarkable; therefore, it cannot be surpassed when assessing women’s health. Nevertheless, autocrine control associated with stimulation and environmental factors that might affect the hormonal secretion or autocrine control can delay and affect lactation.

Besides, the preparation that comes with having a baby allows us to understand what a new life needs to excel in this world. Every mother and/or parent wants the best for their children. Indeed, preparation leads to change, a change for the best. Therefore, some of the actions required to improve our health as women and provide the best for our children rely on what we do today. -Ana Paola Rodríguez Arciniega. Master in Clinical Nutrition.


Nowadays, 32% of women of childbearing age have a BMI greater than 30. Overweight and obesity are linked to shorter breastfeeding duration and are less likely to breastfeed.

  • Keep an active lifestyle. Start today, walk for 30 min!
  • Maintain a normal BMI. Start today, quit soda. You already did? Add vegetables to every meal, have a breakfast smoothie.
  • If you have problems losing weight, look for professional guidance.
  • Prepare your meals in advance. You will be less likely to go hungry and eat whatever is available. Start today. It is cold, right? How about chicken, vegetables, and rice soup. Let’s cook a double batch.
  • Assess your health periodically.
  • Maintain a close link with your community, family, and friends. If it is going to be a long journey, travel with someone.
  • Practice self-care. Start today with a guided meditation.
  • Please keep it simple and manageable; make it possible.
Assess your genes

Knowledge and technology can work together and provide a better understanding of the hormonal status and how to improve it. DNA life with DNAoestrogen can aid patients and healthcare providers to achieve a balanced and optimal hormonal status through personalized testing and treatment.



Sriraman, Natasha K. “The nuts and bolts of breastfeeding: anatomy and physiology of lactation.” Current problems in pediatric and adolescent health care 47.12 (2017): 305-310.

Truchet, Sandrine, and Edith Honvo-Houéto. “Physiology of milk secretion.” Best Practice & Research Clinical Endocrinology & Metabolism 31.4 (2017): 367-384.

Wambach, Karen, and Becky Spencer. Breastfeeding and Human Lactation. 6th ed., Jones & Bartlett Learning, 2021.


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