Hormones, part three: stress and love

    Today , Atlas will talk about more famous hormones - cortisol, oxytocin, melatonin. We meet with their action every day, but as always - many of them do not work exactly as we expected.



    Cortisol


    This is a steroid hormone that is secreted in the adrenal cortex under the influence of adrenocorticotropic hormone (ACTH). Like all steroids, cortisol is able to influence the expression of other genes - and its quality largely determines its importance.

    Cortisol is synthesized as a result of the body’s response to stress, and the hormone’s task is to accumulate the body’s forces and direct them to solve the problem. Cortisol has a “younger brother” - adrenaline, which is also secreted in the medulla of the adrenal glands. Adrenaline provides an instant reaction to stress - pressure rises, heartbeat quickens, pupils dilate. All this is needed to conduct a quick “hit or run” reaction. Cortisol is slower and works longer distances.

    Under the action of cortisol, the blood sugar level rises, the work of the immune system is suppressed (in order not to expend energy), gastric juice is secreted. Increased over time, cortisol slows down the healing of wounds and can stimulate inflammatory processes in the body. Cortisol also reduces the activity of building bone tissue and collagen synthesis.

    Under the influence of sunlight on the pituitary gland, the level of cortisol begins to rise shortly before waking up and helps the person to wake up, full of energy. During the day, cortisol helps us to cope with normal stress (it is called eustress). This includes any tasks that require our reaction: respond to a letter, hold a meeting, prepare statistics. Eustress does not harm our health - on the contrary, it is a necessary level of load.

    But when the level of stress begins to go off scale, eustress turns into distress - stress in its everyday sense. Initially, these were life-threatening situations, but now any events have been added to them, to which a person attaches great importance. It can be overwork at work, problems in relationships, failures, worries and losses, as well as a wedding, relocation, Nobel Prize award or just a million dollars - stress is not necessarily bad events, but any changes in circumstances that require changes from us. Evolutionarily, a person is prepared to respond to stress, but not to be in it constantly. If a stressful situation stretches over time, permanently elevated cortisol levels begin to negatively affect the body.

    First of all, the hippocampus suffers, synaptic connections are destroyed, brain volume decreases: these processes impair mental and creative abilities. Under the action of cortisol, especially at an early age, methylation occurs — some genes can be “turned off”. Children who have been subjected to severe stress as a child or have not received enough maternal care will change their ability to learn - and these changes will last for a lifetime. Memory in such a case would be better to keep negative impressions, so the training of these children is better under the pressure of stress, whereas ordinary children need a safe environment.

    Also, the prolonged effect of cortisol leads to a weakening of the immune system and the activation of inflammatory processes. That is why, after a nervous meeting or a sleepless night, a “cold” may appear on the lips - a manifestation of the herpes virus, which according to statistics is approximately 67% of the population, but which doesn’t show itself in peacetime. Chronic stress leads to the early manifestation of signs of aging due to the fact that cortisol blocks the synthesis of collagen, weakens and dehydrates the skin.

    Warm hugs, sex, favorite music, meditation, jokes and laughter will help reduce cortisol levels. Well helps how to sleep well - and it is important not so much the amount of sleep as its quality. If you have offended someone or quarreled with loved ones - reconciliation will reduce cortisol levels to background values.



    Prolactin


    It is a peptide hormone known for its defining value for lactation. The pituitary gland is mainly responsible for its synthesis, but in addition to the brain, prolactin also synthesizes the placenta, mammary glands and even the immune system. The level of prolactin increases many times during pregnancy, childbirth and, most importantly, when breastfeeding. Attaching the baby to the breast and nipping the nipple stimulates the production of colostrum (a natural protein shake with a high content of immunoglobulins that the mammary glands secrete in the first few days after birth) and the transformation of colostrum into milk. Despite the high level of prolactin during pregnancy, lactation begins only after delivery, when the level of progesterone falls, which previously prevented the launch of the “dairy plant”. Also, a high level of prolactin blocks the synthesis of follicle-stimulating hormone, which is necessary for ovulation. So regular feedings become a natural hormonal "contraceptive".

    But the lactation effect of prolactin does not end there: it is also a stress hormone. Its level rises in response to anxiety, severe pain, and exercise. Prolactin has an analgesic effect in inflammatory diseases and, unlike cortisol, it activates the immune system - stimulates stem cells to hematopoiesis and participates in the development of blood vessels.

    The level of prolactin rises during crying and orgasm. A high level of prolactin blocks the dopamine  D2 receptors , and dopamine, in turn, blocks the secretion of prolactin: from the point of view of evolution, nursing mothers needless curiosity and desire to learn new things.



    Oxytocin


    This is an oligopeptide hormone - it consists of several amino acids. It is synthesized by the brain section of the hypothalamus, then it is secreted in the pituitary gland.

    In women, oxytocin is released during childbirth - it contributes to the reduction of the uterus in the first and second stages of labor. A synthetic version of the hormone is even used to stimulate childbirth. Oxytocin reduces sensitivity to pain. In the postpartum period, under the action of the hormone, the bleeding stops and the fractures heal. The level of oxytocin increases many times during lactation - here the hormone acts along with prolactin. The activity of oxytocin receptors also regulates estrogen receptors.

    In both women and men, oxytocin plays an important role in sexual arousal. The level of oxytocin increases the embrace (any - not necessarily with sexual overtones), sex and orgasm. Oxytocin is considered a hormone of affection - it evokes a feeling of trust and calm along with a partner. Although to the same extent, oxytocin can be called a hormone of carelessness: it reduces the perception of alarm signals and fear (but does not affect the causes of such signals).

    Oxytocin is a well-known stress fighter: it blocks the release of adrenocorticotropic hormone (ACTH) and, as a result, cortisol (ACTH gives the signal to produce cortisol). Therefore, under the influence of oxytocin, a person feels safe and opens up to the world. The work of oxytocin receptors depends on how much each of us is able to experience empathy. People with a less active version of the OXTR gene will find it harder to understand the feelings of others and share experiences. According to studies , this mechanism plays a role in the development of autism.

    With the participation of oxytocin, a rather ancient mechanism of forming social bonds in animals is carried out - this is due to the upbringing of offspring and the need to protect the mother during this period. The main role of oxytocin is in the formation of a mutual connection between mother and child and between partners. On the basis of his relationship with the mother or any other person who cares about him, the child forms ideas about himself and his personality. The obtained knowledge and experience helps to predict the consequences of actions and form a picture of the world. Oxytocin is also involved in learning.



    Vasopressin


    Vasopressin is another peptide hormone of the hypothalamus. Vasopressin is also called an antidiuretic hormone - it regulates the water balance in the body: it reduces the absorption of water by the kidneys and retains fluid in the body. Vasopressin reduces vascular smooth muscle and may increase blood pressure. Decreased vasopressin secretion can cause diabetes insipidus - a disease in which a patient is given a huge amount of fluid (more than 6 liters per day) and constant thirst.

    Vasopressin plays the role of a neuropeptide and acts on brain cells. It influences social behavior. Thus, the variant of the vasopressin receptor gene AVPR1A is associated with the likelihood of happy family relationships in men - this conclusion was made when comparing datagenotyping and survey results. Experiments were conducted on mice that showed that stimulation of vasopressin receptors makes males more attached to their females — they preferred to spend more time with a familiar partner, even if they had previously differed in polygamous behavior. It should be noted here that in animals, social monogamy has nothing in common with sexual - it is about attachment to a partner, and not about the complete absence of “extramarital” connections. In humans, the action of vasopressin as a neuropeptide is not so straightforward.

    Oxytocin and vasopressin are paralogs: substances that were created as a result of doubling the DNA sequence and are very similar to each other. Vasopressin begins to be synthesized in the fetus from the 11th week of pregnancy, oxytocin - from the 14th week, and both continue to participate in the development of the infant during the postnatal period. The high expression level of vasopressin receptors in the neonatal period can lead to increased aggression in adults.

    If the level of oxytocin can vary greatly depending on the situation, then vasopressin is a hormone with a smaller range of changes, the level of which mainly depends on genetics. From the activity of vasopressin receptors and their genetic variants depends on the formation of social behavior and stable (or not) connections between partners. Also, these receptors are involved in the development of long-term memory and affect the plasticity of neurons in the cerebral cortex.



    Melatonin


    Let's finish today's story on a joyful note - let's go to sleep. Melatonin, a sleep hormone, is produced by the brain’s epiphyse when it gets dark (which is why it’s a bad idea to shine a smartphone’s screen before bedtime). It regulates the “internal clock” —circadian rhythms — and helps all body systems go into rest mode. During the day, the highest level of melatonin falls on the period from midnight to 5 am on a light day; during the year, melatonin levels rise in winter.

    In the body, melatonin is preceded by the amino acid tryptophan, which also plays the role of a precursor of serotonin. Melatonin slows down aging and reproductive functions and increases serotonin levels. A special role is played by the interaction of melatonin with the immune system - the action of the hormone reduces inflammation. Melatonin has an antioxidant effect and protects DNA from damage.

    Thanks to melatonin, the daily regimen is restored after changing the time zone or night work. A decrease in melatonin production — for example, due to bright light or a change in daily routine — can cause insomnia, which increases the risk of depression. To help your body sleep well and restore regimen, try to sleep in the dark - with the lights off and the curtains drawn, if you have to sleep during the day.



    Life in a big city sometimes consists entirely of stress, chronic lack of sleep, traffic jams, tardiness, meaningless work meetings and tasks of exaggerated importance and urgency. In such a rhythm it is very difficult to find time to recover, so we simply begin to perceive the state of chronic fatigue as a given. But nature did not prepare us for this, and the same cortisol will not stand out forever: if you are constantly under the pressure of stress, over time, cortisol is depleted - and then the body is forced to respond to stress by other methods.

    To make sure that your health corresponds to your stress load, consult with an endocrinologist : your body may need support. And definitely need a rest.

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