What Hormone Makes Milk Flow? Unraveling the Mystery.

Milk is such an important part of our daily lives, with its nutrition benefits that help to build healthy bones and muscles, ameliorate risks of diseases, protect the body’s immune system and serve as a significant source of energy. As much as people rely on milk for survival, there’s always the question of what hormone is responsible for milk production. This article sets out to unravel this mystery, so let’s get started.

What is Milk Letdown?

Milk letdown refers to the process of milk flow out of the mammary glands. It occurs when prolactin, oxytocin, and other hormones work together to move the milk from the breast tissue through the ducts to the nipple. Prolactin and oxytocin are the primary hormones responsible for milk production.

Prolactin: The Hormone Responsible for Milk Production

Prolactin is a hormone produced by the pituitary gland that triggers milk production in the mammary glands. It is secreted in larger quantities during pregnancy, and after delivery, the hormone level spikes to increase milk production. Additionally, a breastfeeding baby can also stimulate prolactin release as it sucks the breast.

Higher prolactin levels lead to the increased secretion of milk, and low levels can result in inadequate milk supply. To increase milk production and maintain a steady lactation supply, stimulating prolactin production is necessary. This can be achieved by regularly breastfeeding or pumping breast milk.

Oxytocin: The Hormone Responsible for Milk Ejection

Oxytocin is responsible for milk ejection during breastfeeding. This hormone is produced in the hypothalamus and secreted by the pituitary gland during breastfeeding. Sucking of the breast triggers the release of oxytocin in the bloodstream, which causes the muscles surrounding the milk ducts to contract, pushing the milk out through the nipple. The feeling of milk letdown when the milk flows is a response to oxytocin.

Oxytocin also plays a significant role in the bonding between mother and baby. Producing a sense of serenity, the hormone plays a vital role in building trust, bonding and relaxation, encouraging the mother’s milk flow, and a potential beneficial impact on breastfeeding outcomes

The Stages of Milk Production

Milk production occurs in stages, which are:

  • Stage 1 (Colostrum Production): Colostrum is the first milk produced. It is yellowish, thick, and high in nutrients than regular breast milk. Produced during the final stages of pregnancy, the milk produced is smaller in quantity but high in essential nutrients, including antibodies for the baby immunity.
  • Stage 2 (Transitional Milk Production): After colostrum comes transitional milk, usually within three to four days after delivery. This milk is less yellow and has a more watery texture, while it still contains essential nutrients and antibodies for the baby immunity.
  • Stage 3 (Mature Milk Production): Mature milk is produced after transitional milk, within ten days following delivery. It’s white, creamy, and has a balanced nutritional content, a perfect blend of fat, protein, and carbohydrate for the baby to grow optimally. The breast continues to produce mature milk until long term breastfeeding is established.

Factors That Affect Milk Production

Several factors influence milk production, some of which are:

  • Breastfeeding frequency: Frequent breastfeeding prompts more oxytocin and prolactin secretion, leading to enhanced milk production.
  • Stress: High-stress levels can negatively affect the release of milk letdown hormones, thereby reducing milk production.
  • Diet: A healthy and nutritious diet, including vitamins and minerals, is necessary for optimal milk production.
  • Breastfeeding technique: Proper breastfeeding technique can enhance milk production.
  • Medical Conditions: Conditions such as diabetes, PCOS, hypothyroidism, hormonal imbalance can affect milk production, and seeking medical advice is necessary.


Prolactin and oxytocin are the primary hormones responsible for milk production and milk letdown, respectively. Milk production occurs in stages, starting with colostrum production, followed by transitional, and finally mature milk production. Some factors affect milk production, including adequate diet, breastfeeding frequency, less stress, proper breastfeeding technique, and medical conditions. Mothers can ensure optimal milk production, by applying good latch techniques, meeting with lactation specialists or seeking help, and by consuming a well-balanced diet or taking necessary supplements as prescribed by a medical practitioner.

Frequently Asked Questions About What Hormone Makes Milk Flow?

Here are some common questions and their answers about what hormone makes milk flow:

  • What hormone triggers milk production in lactating mothers? Prolactin is the hormone responsible for milk production in lactating mothers.
  • What hormone is responsible for milk letdown? Oxytocin is the hormone responsible for milk letdown. It causes the muscles surrounding the milk ducts to contract, leading to milk ejection.
  • What factors can negatively affect milk production? Several factors can negatively affect milk production, including stress, lack of adequate nutrition and breastfeeding frequency, improper breastfeed latching technique, and medical conditions.
  • How long does it take to see milk production? Milk production usually begins between 30 to 40 hours after delivery. Initially, colostrum is produced, gradually transitioning to mature milk over a period of ten days.
  • Can stress affect breastmilk supply? Yes, high-stress levels can negatively affect breastmilk supply by reducing milk letdown hormones, such as oxytocin.


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