Estrogen may induce breast cancer
Preface
We chose this topic because for us it is very interesting and an up to date topic. In this paper we wanted to get a better knowledge about estrogen, what preparations that contain higher level and what risks it may has on a human body. We have used textbooks and mostly medical articles posted on pubmed.com to get more information.
Introduction
Breast cancer is the most common type of cancer among women in the Western world, and breast cancer incidences have increased by 2-3 % annually during the past 50 years. Several factors are playing a role in how women around the world get breast cancer, both lifestyle and genetics inherited play a crucial role. Several studies have been done proving that prolonged intake of the hormone estrogen over several years may increase the possibility to develop breast cancer. Estrogen intake in form of birth control pills and HRT (hormone replacement therapy) linked to menopause is the most common used preparations.
Physiology background
Estrogens are hormones which occur naturally and synthetically and are principally associated with ovarian cycle, pregnancy and parturition together with progesterone and gonadotropins. The most important hormones are those belonging to the group of steroids and are produced by the granulosa cells of follicles in the ovary, placenta and adrenal cortex in women. Estrogens comprises of estradiol-17β, estrone and estriol where estradiol is the most predominant in both pregnant and non-pregnant.
Estrogen regulates the proliferation of normal and neoplastic breast epithelium. It triggers its effect on women genital development and the organism as a whole and is also to be found in bone structure. Some of its tasks relevant to this topic are to stimulate follicular development, development of secondary sexual characteristics like breasts by stimulating duct growth, secretory activity of uterine ducts and more.
Progesterone works close with the estrogens and it is a part of estrogens synthesis. It is a steroid sex hormone produced by corpus luteum of the ovary, placenta and adrenal cortex. Main task is to ensure secretory changes in the uterus in the other half of the menstrual cycle. In this way the uterus is ready to receive a fertilized egg. Progesterone also acts relaxing on the musculature of the uterus that will prevent repelling of the fertilized egg. Also promotes endometrial gland growth.
Both progesterone and estrogens are steroid hormones which are synthesized from the cholesterol in the blood. The pathway starts with the: cholesterol → pregnenolone → progesterone → testosterone → estrogens, (from the textbook “Functional anatomy and physiology of domestic animals, 4th edition”).
The estrous cycle starts after puberty and is the period between two subsequent ovulations. It consists of four phases: proestrus, estrus, metestrus and diestrus. The length of estrus cycle in humans is 28 days and in mammals usually 21 days, but it differs from species to species. The estrous cycle is interrupted by pregnancy. Estrogen level is highest near the end of the follicular phase right before ovulation (menstrual cycle).
Estrogens have two receptors named ERα and ERβ and they are very alike in the amino acid level in both the DNA binding domain and the ligand binding domain. They are represented in many tissues, in some organs they are equally and in others one of them predominates. At the same time they may be represented in the same tissue, but in different cell types. The ERα is mainly represented in the uterus, ovary (theca cells), bone, breast, liver, white adipose tissue and more. While the ERβ is mainly represented in colon, ovary (granulosa cells), bone marrow, salivary gland, vascular endothelium and more.
General about breast cancer
Breast cancer is a cancer type that develops from breast cells. Majority of breast cancer occurs in females and it is the most common invasive cancer in female World Wide. The breast consists of billions of microscopic cells. Under developing of breast cancer these cells multiply uncontrollably. Again, you have two subtypes which are determined by their location. The most common type is the one that begins in the lactiferous duct, also known as the milk duct. The second type begins in the lobules and is much less common.
Invasive breast cancer type is when the cancer cells break out from duct or inside the lobules and act on nearby tissue. The cancer cells may reach the lymph node and finally spread to other organs like liver, bones, lungs, and to other parts of the body by the blood stream and lymphatic system.
The non-invasive breast cancer does not break out of their origin place, but are still inside the lobules/milk ducts. They may develop into invasive breast cancer.
Symptoms of breast cancer can be felt by the patient by having a lump in the breast, an area of thickened tissue, redness in skin around the breast, pain in armpits or beast that does not seem to be related to the woman’s menstrual cycle.
Why some develop breast cancer and others do not is not easy to say, but some risk factors can impact in a woman probability of developing breast cancer. The risk of developing breast cancer increases with age, most likely when the age 50 has past and after menopause. Genetics may also play an important role. Canadian National Breast screening study followed 27.318 women who had or have had a family member with breast cancer. They found 1.707 cases. Some genes can be inherited (like BRCA1 and BRCA2 genes). If a woman has had breast cancer, the risk of getting it again is higher compared to woman who has no history of the disease. Use of estrogen preparation also increase the risk of develop breast cancer.