Estrogens: Types, Functions And Effects In The Body

This group of sex hormones have various effects on the bodies of men and women.

Estrogens

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, secreted naturally by the body, are estradiol, estrone, and estriol.

Characteristics of estrogens

Estrogens 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 the growth of the breasts.

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 the chemical level, the estrogen molecule is based on the structure of phenanthrene (type of chemical structure).

Regarding its biosynthesis, it includes the aromatization of testosterone by the aromatase enzyme. Aromatase is present in many tissues, including adipose and the brain.

Types of estrogens

According to its type of synthesis or origin, we can speak of 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:

  • Ethinylestradiol : of great estrogenic power, it is very active orally.
  • Mestranol – Generally used in conjunction with progestogens.
  • Quinestrol.

3. Non-steroidal synthetic estrogens

They are not steroids, and they are active orally. They have a certain chemical similarity to steroids and are capable of activating potent estrogen receptors, so they are of great therapeutic use. The main ones are three:

  • Dienestrol : is used or was used to treat symptoms of menopause.
  • Diethyl ethylbestrol or ethylbestrol: it is the best known and classic.
  • Chlorotrianisen : in the body, it is transformed into a long-acting active estrogen (proestrogen).

Mechanism of action and functions

In humans (and in 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 main 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 work in the body? The mechanism of action of estrogens has to do with the nuclear receptors of cells. Its function is to regulate gene expression, as well as to promote the synthesis of specific mRNA (messenger RNA).

Furthermore, estrogens induce the synthesis of receptors for the production of progesterone in cells of different tissues.

Effects on men and women

The effects of estrogens 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 the reproductive organs. If this relationship is disturbed, the reproductive organs may develop incompletely or abnormally.

In women, the function of these hormones is to prepare the uterus to accept the fertilized egg, as well as to help with pregnancy and lactation. 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, estrogens regulate spermatogenesis (synthesis of sperm) in the male reproductive system. However, if the estrogen level in men is high, it can inhibit sperm production.

Pharmacological actions

At the pharmacological level, estrogens have diverse actions. These actions can be specific (when they act in specific places of action, for example in breasts, genitals, vagina, tubes, …) or non-specific (for example in relation to prolactin, thyroid, adrenal, … ).

Let’s see some examples of non-specific pharmacological actions of estrogens:

1. Prolactin

Estrogens increase the synthesis and release of prolactin, a hormone that stimulates the secretion of milk, 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 estrogens 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. Clotting 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 estrogens, we can find different adverse effects in the body:

1. By high concentration

Some of the adverse effects of a high concentration of estrogens are that there is an increase in 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 is drug treatments used for hormone replacement, regulation of the menstrual cycle or contraceptive methods.

2. Due to a decrease in concentration

Two main adverse effects appear: metrorrhagia (unscheduled vaginal bleeding) and amenorrhea (absence of menstruation).

Other treatments in animals

Estrogens, in addition to contraceptive treatments in humans, are also 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.

Bibliographic references:

  • Hileman, B. (1994). Environmental Estrogens Linked to Reproductive Abnormalities, Cancer. Chemical & Engineering News, 72 (5), 19-23.
  • Ramírez-Sánchez, I., Martínez-Austria, P., Quiroz-Alfaro, M. and Bandala, E. (2015). Effects of estrogens as emerging pollutants on health and the environment. Water Technology and Sciences, 6 (5), 31-42.

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