Understanding Breast Involution 
by DrJim

The purpose of this discussion is to show that sometimes there is a good rationale to do hormonal induction when the desire is to produce a significant quantity of milk with lactation. During pregnancy the breasts are hormonally induced. It is true that women can induce lactation at virtually any time in their life with nipple stimulation alone and without any herbs, drugs or hormones. It is not true however, that they will always produce a significant quantity of milk. Many physicians that advise women on how to lactate as a surrogate mother advise starting with a course of hormonal induction. 

First, what is breast involution? It is the process by which the breasts undergo the reverse of development and become smaller with fewer alveoli and become less ready for lactation. The number of alveoli in the breasts is the critical factor in making milk. The breasts always undergo involution to some degree when they return to a resting state after lactation. 

Normal Breast Development

The development of the breasts starts with the development of a branching duct system under the influence of Estrogen. In association with the ducts, the connective tissue develops which supports the breast and is known as “Coopers ligaments”. This connective tissue surrounds each lobule like the membranes around each orange segment. A certain number of fat cells also develop in the breast tissue under the influence of Estrogen. Progesterone causes a further more complex development of the breast tissue. If Estrogen has not first stimulated the breast tissue to develop then Progesterone will have no significant effect. Under the influence of Progesterone the breasts develop alveoli on the branching duct system already present. The nipples enlarge as well. Prolactin then causes further development with the addition of little muscles to the alveoli so that they may contract and eject the milk. The areola enlarges and becomes darker and the ducts become more round and open. Further stimulation by Prolactin will turn on the Alveoli to produce milk. When breasts undergo involution they tend to follow this process in reverse. Alveoli stop producing milk, they then loose their muscles necessary to contract to eject the milk. The ducts collapse but remain a potential channel, although still present they may not be able to transfer fluids. The number of alveoli decreases reverting to fat tissue. The ability of the duct system to shorten and become less developed is limited but may occur under some conditions with some women. Most of the time when breasts undergo involution with a decrease in volume and amount of glandular tissue the duct system does not shorten and the breasts become thinner and pendulous. If the duct system shortens the breasts can become small but retain their more perky shape. When breasts become smaller plenty of Growth Hormone through exercise can help the duct system to remodel and shorten.

 What the Apes teach us about Involution

Generally the great apes including gorillas and chimpanzees do not have breasts except when they are breastfeeding an infant. During their pregnancy the breasts are induced and grow to full functional size. After the birth they breastfeed the infant until it is weaned. When the infant is weaned their breasts dry up and undergo involution down to a very small dormant size not much bigger than prior to the pregnancy. The nipple alone remains developed somewhat. In the time between rearing infants the females are not encumbered with breasts as human females are. Their hormonal state is more similar to that of a human female athlete who undergoes vigorous continuous training and maintains low hormonal levels with sometimes cessation of menses. Almost all mammals, other than humans do not maintain breasts that are capable of lactation at times other than when they are actually breastfeeding an infant. You could say that for mammals other than humans, breasts are utilitarian, serving the single purpose of nourishing an offspring until it is capable of eating independently. This brings us to the consideration of the dual purpose for breasts in humans.  

The hormonal cycle in chimpanzees and gorillas, our nearest relatives, causes the females to have long periods of time between ovulation when they are not able to become pregnant. They are not receptive to copulation except when they come into their Estrous. Human females are balanced hormonally a little differently and are essentially continuously receptive to having sex. In the human male-female bonded relationship sex plays more than just the utilitarian purpose of procreating an offspring, are we not glad?! Breast development also follows this difference in hormonal makeup. The breasts of apes go away, involute to almost a prepubertal state while human female breasts stay developed and capable of lactation continuously. Surely this might suggest there is a purpose for breasts other than just nourishing an infant! Surely they play a part in maintaining a relationship with their mate as well as nourishing an infant. Humans could be like the apes where their breasts involute all the way down to a nipple only between child rearing events, but they are not. 

Of course many of the functions in the apes also apply to humans. Here is an interesting side note. When a female ape that does not have an offspring associates closely with another female who is breastfeeding an infant, she will sometimes develop breasts and start lactating and join the mother in a shared relationship to breastfeed the infant. With humans there have been cases of young single women who have worked closely with lactating mothers who have begun to spontaneously lactate themselves. In both of these situations lactation is induced through the influence of pheromones. Pheromones generally have a stronger influence in species that rely more upon the sense of smell (which means almost all but humans) since pheromones work thorough the olfactory system. 

Postpartum Involution of the Uterus and Breasts

After birth the uterus is very large, about 10 inches in diameter in comparison to the normal non-pregnant size of a small fist. This large uterus undergoes fairly rapid involution where the numbers of cells and amount of muscle tissue decreases until the uterus is remodeled back to a non-pregnant condition. The high hormonal state of pregnancy induces the breasts in preparation for lactation. After the birth Estrogen and Progesterone become low while Prolactin is high. This induces the breasts to lactate and as long as breastfeeding continues the breasts will remain fully populated with active alveoli. If the mother chooses to not breastfeed, the breasts will dry up and the low hormonal state will cause the breasts to involute back to their prepregnant state. Some women lament saying “After I had a baby my breasts ended up smaller than they were before I was pregnant.” Most women do not end up with smaller breasts after they have completed their post-partum state, but some do. This is due to a stronger involution process at work in them than the average. Human breasts involute after a pregnancy and breastfeeding like the apes do only they do not involute nearly as far. They maintain a partial development reflected by the differences between the human and the ape and the way their hormones cycle.

 Breast Changes with Age

At puberty the breasts start developing and enlarging, primarily under the influence of Estrogen. Most girls do not ovulate initially and may take 2 years or more before they ovulate regularly. Progesterone is only produced with ovulation so initial breast development is dominated by Estrogen. The breasts enlarge while the nipples remain small. Because the duct system is elongating they usually develop “puffy nipples” which include an elevated areola above the breast surface. The breasts are not fully populated with alveoli at this time. During the late teen years high hormonal levels with regular ovulation add some alveoli with each hormonal cycle. Over several years the breasts fill out, enlarge and mature to their fully developed state. The puffy nipples go away as the breast becomes flush with the areola. The breasts reach their full development and size somewhere between the ages of 17 and 24. They have the most alveoli of any time except pregnancy. Hormonal levels are the highest of any time in life around age 24 except during pregnancy. Girls that get pregnant before their breasts are mature can lactate successfully because the pregnancy induces their breasts to fully populate with alveoli. Let it be said however, that it is not good for teenage girls to be pregnant or induce lactation or any such thing because their bodies are not fully mature and ready. Women who are in their early 20s would find it very easy to induce lactation because of the readiness of their breasts and the large number of alveoli present. For them stimulation alone should be able to bring about significant lactation within a short time, as little as a single monthly cycle. The main factor that would inhibit successful lactation at this time is the fact that their Estrogen levels are so high and their ovaries are so active. Estrogen inhibits Prolactin release and a very effective way to lower Estrogen is to take a Progesterone supplement. Some may have to use Domeperidome to help increase Prolactin as well, but most should not. 

From the early 20s until the time of perimenopause around age 40 to 50, the hormonal state is characterized by a steady waning of hormone levels. Most women ovulate with regular menses and thus produce regular amounts of Progesterone. Even though the breasts remain fairly stable and constant in their development, there is a small but steady loss of alveoli. The breasts actually steadily decrease in size in the actual glandular development. This fact is confounded by the fact that insulin levels for the average woman increase during this time along with weight and body fat ratio. Of course the breasts enlarge with the increased amount of fat. Women who are in their 40s have less dense breasts than women who are in their 20s as noted by mammograms. This means they have more fat and less gland and connective tissue. Women in this period will find that it takes longer to induce lactation and the amount of milk produced will be less that what they would have had when they were younger. They are usually successful at inducing lactation with stimulation and the use of some aids including Domeperidome and some herbs. For many women in this period a short course of hormonal induction can wake up their breasts and increase the number of alveoli and subsequent amount of milk produced. Some women age more gracefully during this period and maintain higher hormone levels. These women will likely have a later menopause and more success at inducing lactation when not taking hormones. On the other hand, smoking and various diseases that are associated with aging tend to put a stress on the system and cause lower hormonal levels and earlier menopause than would otherwise occur. 

From the onset of perimenopause and into the late years of life the breasts undergo a steady and more rapid involution. With perimenopause ovulation becomes intermittent and average Estrogen and Progesterone levels become much reduced. With menopause Estrogen becomes even lower and Progesterone drops to nothing. During this time the breasts loose alveoli, the ducts collapse and the entire glandular structure eventually reverts to fat and connective tissue only. Here again, some women age more gracefully and this process may be slower and they may maintain the ability to induce lactation to some extent. Younger women who have had a surgical menopause and women who have gone through menopause recently are likely to still have a significant number of alveoli. They may still want to consider a short course of hormones to help them in inducing lactation and should be able to do so as their bodies are still able to handle the hormonal stimulation easily. This certainly makes sense if they want to be a surrogate mother to an infant. For those who want to induce lactation for an adult nursing relationship it must be remembered that the milk is only a minor part of the experience so hormonal induction is more of an optional consideration. 

The more time past menopause there is, the more likely they will need a course of hormones to successfully produce milk. A short course of higher hormonal levels has a lower cancer risk than the prolonged use of hormones in the postmenopausal years. When a woman is many years past menopause, using hormones to wake up the breasts is generally not a good idea because hormonal stimulation can be a stress on their system. It is like trying to rev up a tired old engine in a car that has too many miles on it. This varies greatly from individual to individual however, because aging in the later years of life has much more to do with overall health and lifestyle issues. It is the biological age, not the chronological age that should determine these decisions. 

So, inducing lactation is always best just using stimulation, some herbs and perhaps some Domeperidome. When satisfactory success does not come from this alone, then considering ones age and health and other factors as noted here may lead one to consider a short course of hormonal stimulation.

DrJim

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