Wednesday, July 29, 2009

Hormones in breast milk prt1: "Typical' hormones

While I was at EIT I was asked about hormones in breast milk. I was unable to answer it on the spot, so here is.

This post will look at Nonpeptide hormones. This group of hormones are the ones which do not contain or use proteins. (peptide is the name for a small protein). These makes most of them fat soluble hormones, which most of us think of when someone says hormones. Start with the more familiar hormones, and ending on the least familiar. I have tried to pick up the functions of these hormones that might be important to baby.

Sexual hormones
  • Progesterone. Although it is the drop of progesterone is one of the triggers for birth and it is this drop that allows lactation, progesterone is still present in fill breast milk. Like any hormones it has a gizillion functions. Somewhat ignoring its sexual functions it is thought that is hormone could be modified to a hormone that might improve brain development and memory. As it relaxes smooth muscles tissue it helps reduce spasms, regulates mucous production and enlarges bronchial tubes. This has got to be great as when baby gets all clogged up in air passage ways it makes life much harder for parent(s)!
  • Estrogens. There are three major types of estrogen. They increase bone formation, help with blood clotting and promotes wound healing (this could tie into, or even overcome lower vitamin K levels?!)
  • Oral contraceptive hormoes. Although this is not surprising, it is disturbing that these are found at "biologically significant levels" in breast milk. Not only is it the increase in hormone levels of estrogen, it is that progesterone used in contraceptives is a synthetic types, instead of a natural type. Progestin instead of progestorne is used, likely because it is cheaper.
Adrenal gland hormones:
  • Cortisol. This is the "stress hormone". This is fasinating as when mum is stress or upset baby tends to become this way also. I had assumed that this was an emotionally driven change, but cortisol may also play a part in this. Cortisol also increases copper carrier proteins, which are thought to play a part in immunity. It also helps with detoxification.
Thyroid hormones:
  • Thyroxine. This hormone is made using iodine, and is carried about the blood in a special protein. Interesting enough it is said "Lack of iodine is a major problem in developing countries and is considered to be the world's number one cause of preventable intellectual disability in children." I wonder if baby receives more iodine via this hormone? Anyway this hormone is associated with increasing Nerve Growth Factor (a Nobel prize was given to the people who discovered this factor) which make the Sympathetic and Sensory neurons grow. The sympathetic nerve system is like the autopilot of the body, it keeps everything ticking over without any input. The sensory nerves surprise surprise are the nerves that take the five sensory information and transports it to the central nervous system. As baby is growing both of these nervous systems rapidly it would be logical to assume that thyroxine is an important hormone!
  • Triiodothyronine. Some quotes from Wikipedia sums this hormone up "It is the most powerful thyroid hormone, and affects almost every process in the body, including body temperature, growth, and heart rate." and it "increases the basal metabolic rate and thus increases the body's oxygen and energy consumption. The basal metabolic rate is the minimal caloric requirement needed to sustain life in a resting individual. T3 acts on the majority of tissues within the body, with a few exceptions including the spleen and testis". Also "affects the cardiovascular system. It increases the cardiac output by increasing the heart rate and force of contraction." Lastly "has profound effect upon the developing embryo and infants. It affects the lungs and influences the postnatal growth of the central nervous system..... It is also important in the linear growth of bones". I guess it is important then!
  • Reverse Triiodothyronine. This hormone blocks the above mentioned hormone. I am unsure if it does anything else.
Now the next logical questions would be:
  • How does this compare to formula, cow or sheep? And what about rice or soy "milks"?
  • What hormones does baby make? And are they enough to swamp/counter act/make milk levels trivial in comparison?
These are very good questions and unfortunately the answers to them may not even be known right now. It is not yet agreement on what the "normal" levels of the above hormones in breast milk are.

Hormone list taken from the wonderful reference text edited by Robert Jensen titled Handbook of milk composition.

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