Hormone Balance – The Dance of Life

hormone balanceThe synchronization of woman’s life is often characterized by a balance of two opposing hormones, estrogen and progesterone. When in synch a woman’s life can be virtually euphoric which many describe as a balance in the “mind body connection.”   When these hormones are out of balance symptoms can be so significant that they impair the quality of daily living. In order to fully understand the impact of intricate balance between estrogen and progesterone, one must first understand the normal functions of these hormones.

Estrogens are hormones, which means that they function as signaling molecules. A signaling molecule exerts its effects by traveling through the bloodstream and interacting with cells in a variety of target tissues.

There are numerous hormone messages carried by estrogen and continually received by numerous target organs in the body. The breast and the uterus, which play central roles in sexual reproduction, are two of the main targets of estrogen. In addition, estrogen molecules act on the brain, bone, liver, vagina, bladder, skin and heart, to name a few. Estrogens also stimulate the development and maintenance of female characteristics and sexual reproduction, the breast being one of them.

Estrogens act on target tissues by binding to parts of cells called estrogen receptors.
An estrogen receptor is a protein molecule found inside those cells that are targets for estrogen action. Estrogen receptors contain a specific site to which only estrogens (or closely related molecules) can bind.

The target tissues affected by estrogen molecules all contain estrogen receptors; other organs and tissues in the body do not. Therefore, when estrogen molecules circulate in the bloodstream and move throughout the body, they exert effects only on cells that contain estrogen receptors.
In some target tissues, the main effect of estrogen is to cause cells to grow and divide a process called cell proliferation. Estrogen triggers cell proliferation in both the uterus and the breast.

Estrogens effect on target organs

  • Uterus- the specific coded message estrogen sends to the uterus is to stimulate and thicken it by increasing blood flow in preparation for a menstrual cycle. Estrogen also promotes proliferation of the cells that form the inner lining, or endometrium of the uterus, thereby preparing the uterus for possible implantation of an embryo. During a normal menstrual cycle, estrogen levels fall dramatically at the end of each cycle if pregnancy does not occur and the endometrium disintegrates and is shed from the uterus and vagina as a menstrual cycle.
  • Breast- Estrogen’s message to the breast is grow. Breast cells increase in number of cells and rate of multiplication under the influence of estrogen. In breast tissue, estrogen triggers the proliferation of cells lining the milk glands, thereby preparing the breast to produce milk if the woman should become pregnant.
  • Bone- Estrogens play a key role in regulation of bone mass and strength by controlling activity of bone-forming osteoblasts and bone-resorbing osteoclasts. The effects of estrogens are mediated predominantly by the action of estrogen receptors. Estrogen actually improves bone by decreasing bone resorption and increasing bone formation. Bone resorption occurs all the time, it is a natural process in which some special bone cells called osteoclasts reabsorb calcium and thus breakdown bone resulting in an increase of calcium in the blood. Bone is constantly reshaping itself as a response to normal physical stress on bones and estrogen is needed to maintain a proper rate of bone breakdown.
  • Liver- In liver cells, estrogen alters the production of proteins that influence cholesterol levels in the blood. Cholesterol does not readily dissolve in blood, so before it can be transported through the body, it first becomes bound to special cholesterol-carrying proteins called lipoproteins. The liver produces two such lipoproteins, called low-density lipoprotein (LDL) and high-density lipoprotein (HDL). LDL-cholesterol is considered to be the “bad” form of cholesterol because it tends to release cholesterol directly onto the inner wall of arteries, creating the “plaque” that can lead to heart disease. In contrast, HDL is considered to be the “good” form of cholesterol because it inhibits the formation of plaque and carries cholesterol away from the arteries and back to the liver. The net effect of estrogen’s action on liver cells is to increase the amount of HDL cholesterol and to decrease the amount of LDL cholesterol. By increasing HDL and decreasing LDL, estrogen helps to lower the risk of heart disease.
  • Vagina and Urinary bladder- In the vagina, estrogen causes a thickening of the vaginal epithelium, creating a redundant tissue layer, rebuilding the lining of the vagina and urethra by promoting collagen production. During sexual arousal, this redundancy allows the vaginal surface area to expand. The thickened vaginal epithelium, along with cervical mucus secretions and local bacterial flora, also act as physical barriers, preventing infection. In addition, estrogen stimulation increases the glycogen content of vaginal epithelial cells. Glycogen is metabolized by organisms in the vagina to lactic acid, which acts to maintain the vaginal pH at about 3.5 to 4.5.This acidic pH is an important component of a woman’s nonspecific defense against pathogens and prevention of infection. Since the glycogen content of vaginal tissues is increased in the presence of estrogen there is a more acidic environment which allows lactobacillus to be the most predominant bacterium present in the vagina. This acidic environment discourages the growth of pathogenic bacteria and aids in the prevention of vaginal and urinary tract infections.
  • Skin- Skin is an important estrogen target tissue, and through multiple molecular processes estrogens and related compounds regulate skin function and delay skin aging. Topical estrogen increases epidermal thickness, improves skin hydration skin circulation and vascularity, and increases the collagen content and elastic fibers which aids in preventing wrinkling.
  • Brain- Estrogen directly influences brain function through estrogen receptors located on neurons in multiple areas of the brain. Estrogen has been shown to increase cerebral blood flow, decrease inflammatory changes, enhance nerve activity, and exert a variety of actions on many regions of the nervous system that influence higher cognitive function, pain mechanisms, fine motor skills, mood, and susceptibility to seizures; they also appear to have neuroprotective actions in relation to stroke damage and Alzheimer’s disease. At normal levels estrogen prevents depression, increases concentration, maintains normal sex drive and prevents insomnia. Estrogen plays a significant role in women’s mental health and its imbalances can lead to symptoms of mood swings, memory problems, depression, anxiety, insomnia, decreased sex drive and decreased concentration is the result.
  • Heart- The possible mechanisms behind estrogen’s proposed cardioprotective effect include effects on lipoproteins (HDL, LDL), hemostasis/clotting, carbohydrate metabolism, and blood vessel wall tone and reactivity. Changes in lipoprotein levels may account for up to half of estrogen’s benefit with estrogen administration decreasing LDL cholesterol levels by 10% and increasing high-density-lipoprotein (HDL) cholesterol levels by 10%; both variables are major determinants of CHD risk.. Estrogen is preventative against clotting and increases blood flow which reduces the risk or coronary artery disease (hardening of the ateries. This may decrease the risk of vessels becoming narrow and reducing the risk of clotting and stroke. Estrogen may also relax coronary arteries. Transdermal administration of estrogen, seems to offer more of the heart protective effects as it does not stimulate the liver to make more blood clotting proteins and may prevent adverse cardiovascular effects.

Progesterone is also signaling molecule. It also travels through the bloodstream interacting with cells in a variety of target tissues.
There are also numerous hormone messages carried by progesterone and continually received by binding to progesterone receptors of the same target organs as estrogen but the messages have different actions.

Progesterone is a key component in the regulation of normal female reproductive function. Broadly speaking, the major physiological roles of progesterone in the mammal are:

  • Uterus and ovary: release of a mature egg at the time of ovulation, aid in implantation, and maintenance of pregnancy, by promotion of uterine growth and preventing the uterus from contracting (miscarrying)
  • Breast: aids in mammary gland development in preparation for milk secretion before labor and delivery
  • Brain: stimulates the signaling for sexual response, desire and behavior. Recent evidence also supports a role for progesterone in modulation of bone mass and preventing osteoporosis.

The ovary is the major site of synthesis and secretion of estrogen and progesterone and gives rise to cyclical fluctuations in the levels of these hormones in the circulation.  Progesterone effects are mediated receptor binding. Receptor proteins that specifically bind progesterone, and are induced by estrogen.

Progesterone effects on target organs

  • Uterus, Ovary, and Fallopian tube- Progesterone has a central role in reproduction, being involved in ovulation, implantation, and pregnancy. Regulation of uterine function during the menstrual cycle, by control of cyclical changes in growth or thickening of the uterine lining and solely responsible for its shedding at the time of menstruation.  High circulating progesterone levels are important ensuring implantation during pregnancy, but also for maintaining pregnancy by stimulating growth of the uterine lining and opposing the actions of factors involved in contraction of the uterus and preventing miscarriage. This same contraction prevention mechanism aids in the reduction of menstrual cramps.
  • Breast- Progesterone regulates cell growth factors, and growth factor receptors which ultimately decreases breast cell growth. Progesterone is involved in the maturation of breast cells in the development of mammary glands and ducts and also decreases the rate of multiplication of breast tissue cells. High circulating progesterone levels during pregnancy are responsible for inducing marked mammary gland development of the breast in preparation for lactation. Progesterone also promotes normal cell death in the breast which is important in the prevention of cancer.
  • Brain- Progesterone regulates signals in the brain involving sexually responsive behavior
  • Bone- Progesterone appears to modulate bone remodeling, resulting in protection against bone loss. This effect appears to be mediated by progesterone receptors on osteoblasts (bone re-growth/replacement).