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These are the most important hormones in the human body and their functions

In addition to the hormones related to reproduction, there are many others, such as melatonin or oxytocin, that fulfill structural and vital functions.

Hormones circulate through the body controlling virtually all functions. They influence mood, weight, sweating, blood pressure, appetite, hours of sleep, the menstrual cycle, and sexual desire . If they are in balance, they ensure that the organism works like a clock; but if they are not, an imbalance is created that can affect our health. In the following lines, we explain the most outstanding hormones and what they are specifically responsible for in our body .

Hormones aren’t just for teenagers. It is true that in the transition from childhood to adulthood they acquire a special role, since it implies going through a phase of physical and psychological transformations so intense that the work carried out by these chemical messengers becomes more evident. But hormones also have a lot to say in other stages of life.

During menopause, they are especially known for their bad reputation, with all the side effects that the sudden drop in estrogen entails for some women (hot flashes, vaginal dryness, headache). And during pregnancy they surprise with their work, since these substances facilitate childbirth, make milk production possible and even the love that the mother feels for her child.

However, hormones often go unnoticed when they affect our mood, weight, or the fact that our palms sweat more or less . They can also be responsible for all of this, as well as our fatigue , an exaggerated level of stress or a lack of sexual desire . This is so because they are substances that, once they are secreted by the endocrine glands, travel throughout the bloodstream to other cells and organs of the body where they control and regulate their functions.

Hormonal changes or hormonal imbalances?

María Ángeles Gálvez, the coordinator of the Neuroendocrinology Area of ​​the Spanish Society of Endocrinology and Nutrition (SEEN), defines hormonal imbalance as “an alteration in hormonal levels (increases or decreases) due to unnatural causes and with repercussions on the Health”.

In other words, menopause, for example, with hormonal changes (estrogen and progesterone levels drop) that occur naturally in all women between the ages of 45 and 55, would not fall within that definition. However, hyperthyroidism, a disease caused by an overproduction of hormones by the thyroid gland and which causes palpitations, insomnia, menstrual disorders or involuntary weight loss, would.

“Whether due to natural causes —motivated by age and biological processes throughout life—, by lifestyle (obesity) or by a disorder or disease, health problems can appear when too much or too much is secreted little quantity of any hormone”, indicates Gálvez.

Sex hormones and their role in vital stages

There are many different hormones in the human body— more than 80 have been identified —and all of them, to a greater or lesser extent, have important functions. Naturally, as the years go by, the levels of some soar, others remain unchanged throughout life and others decline, either because they are produced less or because the different organs become less sensitive to the hormone. that controls them. These are some of the key moments.

Adolescence of women

Puberty begins between the ages of 8 and 13 in girls, about two years earlier than in boys, and is usually complete by age 17.

At this stage, her ovaries begin to produce estrogen and its levels gradually increase, since the female body needs a large amount for the great physical transformation that she is going to experience: breast development (the growth of the breast bud is the first sign that puberty has begun in girls), growth spurts (estrogen, which stimulates bone cartilage, and growth hormone work together), enlargement of the hips, or menstruation.

Acne also appears, because, although boys secrete more testosterone, women also have this hormone that causes sebum production to be stimulated.

Before puberty, levels of androgens (the male hormones) are low in both girls and boys, but they increase when adolescence begins (although more in boys) and this stimulates the growth of the male. hair or the awakening of sexual interest in girls.


Estrogen also helps control the menstrual cycle. Estrogens vary throughout the month, with the highest peaks in the middle of the monthly cycle (during ovulation), since it is stimulating the uterus for possible fertilization, and lowest when menstrual bleeding arrives, at which time the organism understands that there has not been a pregnancy and they fall back to a minimum to start a new cycle. But this imbalance can be defined as a slight imbalance that will not affect health.


From the moment the embryo is implanted, the ovaries begin to secrete more estrogen and progesterone, although up to the fourth month of pregnancy, they do so in amounts only slightly higher than those produced in the second half of pregnancy. menstrual cycle.

However, from day 60 of gestation, the placenta begins to secrete these hormones in progressively high amounts, reaching a maximum at the end of pregnancy. Maternal estrogen levels throughout pregnancy will reach concentrations 30 times higher than those found in the luteal phase (the period between ovulation and menstruation).

Progesterone levels, which prepare the breast for milk production, also rise, causing the expectant mother’s body temperature to rise and her intestines to work more slowly (hence, pregnant women suffer from constipation). Progesterone increases progressively throughout the nine months, reaching concentrations 10 times higher than those found during the luteal phase.

This increase in estrogen and progesterone also affects serotonin, causing emotional changes in some women: a mixture of sadness, joy, or fear at childbirth.

Androgens also rise, the male hormones that women also have, and for this reason, some hair usually appears on the face, arms, legs, and nipples (it disappears at the latest six months after childbirth). These same hormones, together with the rise in progesterone levels, make the skin more oily and cause some pregnant women to have pimples and in others, it provides a special shine and luminosity.

Shortly after delivery, estrogen and progesterone production stops, reaching values ​​comparable to those present in non-pregnant women.


It occurs with the cessation of ovarian function, which will lead to a sudden decrease in estrogen levels in the blood. This drop is responsible for the appearance of symptoms that accompany menopause: hot flashes, night sweats , vaginal dryness, sleep problems …

Adolescence in men

Testosterone, the main male sex hormone produced in the testicles, is through the roof at this stage of a man’s life. Stimulates the maturation of the reproductive organs, muscle and bone growth, the appearance of pubic and facial hair.

In addition, it is the cause of the development of secondary sexual characteristics, which are traits that stimulate male development and include characteristics that are not part of the reproductive system, such as a change in the voice, which becomes deeper.


In general, after the age of 20, the production of testosterone begins to decrease. The rate of decline of this hormone varies greatly among men. At age 70, some may have levels similar to those of a 30-year-old. Other young men may have low values ​​and develop certain characteristics associated with aging: loss of desire decreased muscle mass, increased abdominal fat, loss of energy loss, osteoporosis, slowed thinking, or anemia. But precisely this gradual decrease makes these symptoms much milder than those of female menopause.

What do these hormones do in the body?

But in addition to the hormones related to reproduction, there are many others that fulfill structural and vital functions. Growth hormone, thyroid, insulin, melatonin, serotonin, and oxytocin are some of the most important.

Growth hormone

“It is the hormone that stimulates growth in the infant stage. In adults, the main functions are related to the maintenance of bone and muscle mass ”, explains María Ángeles Gálvez, from the Spanish Society of Endocrinology and Nutrition (SEEN), about growth hormone .

Its deficiency in adulthood “causes alterations in body composition and influences the quality of life, so that people with a deficiency of this hormone tend to have little resistance to physical exertion, more adiposity and less bone mineral density “, adds Galvez.

The maximum secretion occurs around the 20-24 week of fetal life. After the birth of the baby, the production of the hormone is low until the stage of puberty, in which it increases considerably. Between the ages of 20-30 it begins to decrease and in old age the levels are zero.

Thyroxine and triiodothyronine, the thyroid hormones

Two of the main hormones released by the thyroid are triiodothyronine (T3) and thyroxine (T4). These hormones determine, among other things, a person’s weight (the rate at which our body burns calories), energy levels, internal temperature, skin, hair, and nail growth .

Thyroid and fatigue

Naturally, throughout life the levels of these hormones remain stable, but they can be altered due to diseases such as hyperthyroidism (when the thyroid gland produces more hormones than the body needs) and hypothyroidism ( when it does not produce the necessary ones).

Insulin, the transport of sugar

Insulin is the hormone that transports glucose from the bloodstream to the body’s tissues so that it can later be converted into energy. People with type 1 diabetes can’t make it and people with type 2 diabetes can’t make enough or they make too much, so the body doesn’t respond correctly.

But blood sugar also rises naturally with age. Exactly the average fasting glucose level rises by 6 to 14 milligrams per cc every 10 years after the age of 50, as cells become less sensitive to the effects of insulin. When the level of 126 mg/dL is reached, a person is considered to have diabetes, a disease that affects a high percentage of people over 65 years of age.


Also known as the sleep hormone, since it regulates sleep-wake cycles , melatonin influences our biological clock and is affected by light (levels increase at night and decrease in the morning), but it also stimulates the growth hormone secretion . It decreases with age, but also due to external factors, such as the use of some medications.

The amount of melatonin is not constant throughout life. Production begins at three or four months of age and its levels increase throughout childhood, reaching a maximum between 8 and 10 years of age. After 40-45 years it begins to gradually decrease and, in people over 70, the levels do not exceed 10% of those we had before puberty.


Serotonin is the hormone that raises and stabilizes the mood , controls learning and memory processes and regulates appetite , causing a feeling of satiety and is necessary for the production of melatonin . Men’s bodies generate up to 50% more serotonin than women’s.


Another hormone related to the mind is oxytocin, also called the love hormone , since its levels increase when we have physical contact with another person, generating well-being, relaxation, satisfaction, and self-esteem. It activates the reward centers and is related to pleasure (it occurs during orgasms).

During childbirth, large amounts are released that cause the muscle fibers of the uterus to contract, producing the contractions that allow the birth of babies, as well as helping in the secretion of milk during lactation.


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