Estrogens: Types, Functions And Effects On The Body
The endocrine system consists of the set of organs and tissues of the body, which secrete a type of substances: hormones. Here We will know a type of female sex hormones, estrogens as well as the different types of estrogens that exist.
Hormones are released into the bloodstream and regulate some of the body’s functions. The main female sex hormones, naturally secreted by the body, are estradiol, estrone and estriol.
estrogens They are steroid sex hormones, mainly female, although they are also secreted in men (to a lesser extent). They are responsible for the development of female secondary sexual characteristics, such as breast growth.
The different types of estrogens are produced by the ovaries, the placenta (during pregnancy) and to a lesser extent, by the adrenal glands. The hypothalamic-pituitary axis plays an essential role in its secretion. Specifically, in the ovaries they are produced in response to signals from the brain and other organs both in vertebrates and invertebrates.
Chemistry of these hormones
At a chemical level, the estrogen molecule It is based on the structure of phenanthrene (type of chemical structure).
Regarding its biosynthesis, this includes the aromatization of testosterone by the enzyme aromatase. Aromatase is present in many tissues, including adipose tissue and the brain.
Depending on its type of synthesis or origin, we can talk about three types of estrogens:
1. Natural estrogens
They are those secreted by the body itself. The most important: estradiol, estrone and estriol
2. Semi-synthetic estrogens
They are steroids derived from estradiol. There are three different ones:
3. Synthetic non-steroidal estrogens
They are not steroids, and are active orally. They acquire a certain chemical similarity to steroids and are capable of activating powerful estrogen receptors, so they are of great therapeutic use. The main ones are three:
Mechanism of action and functions
In humans (and all vertebrates), the three main natural estrogens are estrone, estradiol and estriol. Of these three, estradiol is the most potent, as it has the highest affinity for estrogen receptors.
These three major estrogens are secreted primarily by developing follicles in the ovaries, the corpus luteum of the placenta, adrenal cortex, brain, testes, liver and adipose tissue
But how do estrogens operate in the body? The mechanism of action of estrogen has to do with the nuclear receptors of cells. Its function is to regulate gene expression as well as promote the synthesis of specific mRNAs (messenger RNA).
In addition, estrogens induce the synthesis of receptors for the production of progesterone in cells of different tissues.
Effects on men and women
The effects of estrogen are also notable in prenatal and postnatal development, in men and women Thus, the specific relationship between estrogen and androgens (male sex hormones) is needed for the proper differentiation and formation of reproductive organs. If this relationship is disturbed, the reproductive organs can develop incompletely or abnormally.
In women, the function of these hormones is prepare the uterus to accept the fertilized egg, as well as helping with pregnancy and breastfeeding. One author, Hileman (1994), proposed that estrogens decrease the risk of heart attacks and osteoporosis, but increase the risk of breast and uterine cancer.
In men, estrogen regulate spermatogenesis (sperm synthesis) in the male reproductive system. However, if the concentration of estrogen in men is high, it can inhibit sperm production.
Pharmacological actions
At a pharmacological level, estrogens have diverse actions. These actions can be specific (when they act on specific action sites, for example in the breasts, genitals, vagina, tubes,…) or non-specific (for example in relation to prolactin, thyroid, adrenal,… ).
Let’s look at some examples of non-specific pharmacological actions of estrogens:
1. Prolactin
estrogens increase the synthesis and release of prolactin a hormone that stimulates milk secretion, especially when a woman is pregnant.
2. Thyroid
The thyroid gland is an endocrine gland that regulates the body’s metabolism and the body’s sensitivity to other hormones In this case, estrogens at low doses increase its activity (hyperthyroidism), and at high doses, they inhibit it (hypothyroidism).
3. Protein anabolism
The presence of estrogen increases protein anabolism, that is, the synthesis of proteins from amino acids
4. Coagulation
Some of the different types of estrogens also promote blood clotting. Coagulation involves the blood turning into a gel to form a clot.
Adverse effects
Depending on whether there is an excess or a low concentration of estrogen, we can find different adverse effects in the body:
Some of the adverse effects of high concentrations of estrogen are increased cervical mucus (cervical discharge in women), as well as an increase in the size of the uterus. Excess estrogen also causes hypermenorrhea (very heavy menstrual bleeding at regular intervals) and dysmenorrhea (pain before menstruation).
A possible cause of exposure to high concentrations of estrogens are pharmacological treatments used for hormone replacement, regulation of the menstrual cycle or contraceptive methods.
2. Due to decreased concentration
Mainly two adverse effects appear: metrorrhagia (unscheduled vaginal bleeding) and amenorrhea (absence of menstruation).
Other treatments in animals
Estrogens, in addition to contraceptive treatments in humans, also They are used in hormonal therapies with animals (livestock to produce food, and domestic animals).
Some of its therapeutic purposes are: the use of estradiol to induce and synchronize the heat period in cows, or estriol for the treatment of urinary incontinence in bitches.
