The Marion Gluck Clinic


Breastfeeding And Hormones.

Young mother breastfeeding her baby

Breastfeeding is widely regarded as one of the most complex and impressive feats that the body manages to pull off. Not only have you managed to create a baby, but your body is now in charge of producing food for it as well. 

The relationship between breastfeeding and hormones is intrinsic and complex: your breast milk contains very specific hormones that pass from it into you. Your breastfeeding experience also impacts your hormones in other ways, and these bodily functions can wreak havoc on your postpartum biology. 

What hormones are present in breast milk? 

Breast milk contains a wide range of hormones – both those that pass from it into your body, and those that the baby ingests.


Prolactin is the hormone that is responsible for the production of breast milk. It’s found in extremely high levels in colostrum, which is the first form of breast milk that is produced after birth.

After a few days of breastfeeding, levels of prolactin significantly decrease, and the levels of prolactin in the breast milk become roughly equal with the levels that are usually found in blood. 


Thyroxine (T4) is a thyroid hormone, produced by the thyroid gland (which is responsible for many important bodily functions, such as metabolism and energy production). In the early days of breastfeeding, levels of T4 in breastmilk are fairly low, but increase steadily in the first few weeks.

Research has shown that T4 may help a newborns intestines to develop and mature, and during the first few months of life, breastfed babies have much higher levels of thyroxine in their bodies than formula-fed infants do. 

Epidermal Growth Factor: 

The Epidermal Growth Factor (EGF) stimulates cell growth, and is particularly important for the development of the newborn digestive system, and is found in blood, saliva, breast milk, and amniotic fluid. 

Colostrum also contains high amounts of epidermal growth factor, but levels decrease very quickly after childbirth. Naturally, parents with a very premature baby will have much higher levels of EGF in their breast milk for the first month after delivery.


One of the most infamous hormones is cortisol, commonly referred to as the ‘stress hormone’. Cortisol levels in colostrum are high, but quickly reduce, and stay at a lower level as breastfeeding continues. Unsurprisingly, studies have shown that levels of cortisol found in breast milk throughout breastfeeding correlates to stress levels throughout the process –  people who have happy, calm, positive experiences with breastfeeding have lower levels of cortisol in their breast milk. 

Research has also shown that the amount of cortisol that is present in breastmilk can also affect levels of an important antibody called secretory immunoglobulin (sIgA), which helps to protect a baby’s immune system from illness and disease. Since high levels of cortisol are associated with lower levels of sIgA, a high level of stress while breastfeeding can interfere with the healthy, immune-protecting properties of breast milk. 

How many hormones are there in breastmilk? 

In this blog, we’re only able to cover some of the hormones that are in breastmilk, there’s also leptin, insulin, oestrogen, progesterone, gastrin, androgens… The list goes on, and research into the function of each hormone is still ongoing. 


“It’s no wonder that new mothers are encouraged to breastfeed if possible, given the biological complexities of breast milk, and the benefits it can provide. It’s important to remember though, you need to make a decision about breastfeeding based on the health of you and your baby, and if you find breastfeeding overly stressful or physically difficult, you won’t be helping either your baby or yourself by forcing yourself to carry on. Talk to your doctor to figure out what the best choice for you is”.


           Dr Haleema Sheikh, Marion Gluck Clinic. 


How do your hormones change throughout pregnancy and breastfeeding? 

Not only are breastfeeding and hormones intrinsically linked, but your hormones play a vital role throughout all stages of pregnancy, childbirth, and postpartum. 

Unfortunately, our hormones are easily unbalanced, which can lead to some troubling and uncomfortable physical and psychological symptoms. If you’re struggling with your hormones postpartum, it’s important to know that you’re not alone, and plenty of people go through this. Pregnancy and childbirth are incredibly difficult and strenuous processes for your body to go through, no matter how joyous, and you need to give yourself time to recover. 

If your symptoms persist beyond a few weeks however, or if your hormones and breastfeeding are affecting your day to day life, it might be worth talking to a specialist. 

At the Marion Gluck Clinic, we have a number of specialists in women’s health and hormone replacement therapy. Get in touch with us today.





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