Hormones for "dummies"
Why does a person need hormones?
Hormones are biologically active substances that transmit information from organ to organ. They are responsible for sleep, sexual desire, the need for food and other processes in the body. But it is impossible to say how many different hormones there should be in the body. The concept of norm in this case is individual and depends on many factors. About what role hormones play in our lives and what they are, says the biologist Olga Smirnova.
Why do we need hormones?
Hormones are responsible for key body processes: metabolism, growth and development, sexual function and reproduction, pulse rate, blood pressure, appetite, sleep and wake cycles, body temperature and many others.
Hormones are synthesized in the cells of the endocrine glands and tissues of some organs, for example, in the heart or stomach. Such hormones also control the condition of the tissue in which they were formed. For example, leptin is synthesized in adipose tissue and is responsible for suppressing appetite, and its lack leads to obesity.
Lack of hormones, as a rule, turns into deplorable, and in some cases irreversible consequences. For example, with a lack of somatotropin secreted by the pituitary gland, the child remains a dwarf. And lack of insulin is associated with diabetes.
How do hormones differ from other substances?
Hormones are signaling compounds. Unlike nerve cells – transmitters of the nervous system – hormones do not use electrical impulses to exchange information, but are sent to the addressee. If we compare these two types of carriers, then we can say that hormones are part of the wireless communication carried out through the bloodstream, and each hormone binds to cells, tissues and organs in different ways.
The number of hormones in the human body is small, and they themselves are strictly specific: each hormone performs only its own function. This is due to the features of the "receivers" – cell receptors, where hormones should enter. Each type of cell has a certain type of receptors, with the help of which recipient cells "receive and decrypt information" received from the hormone. This process generally resembles a key and lock mechanism.
For example, adrenaline interacts with certain proteins – adrenaline receptors. They are referred to as transmembrane proteins, which are conjugated with G-protein – an intermediary protein that transmits signals from receptors to enzymes of the cell membrane. Only 10-20% of known drugs can interact with them. This indicates the exclusive and exclusive role of adrenaline receptors. For the study of the mechanism of adrenaline in 2012 , scientists from Duke University and Stanford University received the Nobel Prize in Chemistry.
If the receptors are inside the cell, then they interact with hormones that regulate the functions of the gene (some steroids and thyroid hormone), and if the receptors are on the surface of cells, then the action of their hormones is directed at protein and RNA molecules or ion channels of cells.
What are hormones?
Hormones are divided into several classes: protein-peptide hormones, steroids, which are formed from cholesterol, and hormones derived from amino acids.
Hormones from amino acids use tyrosine for their synthesis. Its variety – L-tyrosine – is a part of all proteins of living organisms. And in the adrenal glands and thyroid gland, adrenaline, norepinephrine and thyroxine are formed with the help of tyrosine.
Protein-peptide hormones are hormones that consist of amino acid residues connected by peptide bonds and are encoded directly by DNA. Protein-peptide hormones are synthesized from biologically inactive prohormones, or precursor substances. For example, insulin is formed from preproinsulin: preproinsulin loses 23 amino acid residues from its structure and becomes proinsulin, and losing another 34 – insulin.
The most well-known representatives of protein–peptide hormones are insulin, which maintains a certain level of glucose in the blood and, if necessary, reduces it; glucagon, which raises the level of glucose in the blood; and somatotropin – it is responsible for the growth of the skeleton and an increase in body weight.
The basis of steroid hormones is cholesterol. It and its derivatives do not dissolve in water, so steroid hormones easily penetrate target cells through the bloodstream. They are produced in the adrenal cortex, testes, ovaries and placenta, that is, steroid hormones include hormones of the adrenal cortex and sex hormones.
About 30 types of corticoid hormones are formed in the adrenal cortex. They are divided into three groups. The first is glucocorticoids. Their task is to regulate carbohydrate metabolism, provide anti–inflammatory and anti-allergic effects. The second group is mineralocorticoids, which are responsible for the water–salt balance in the body. And the hormones of the third group are inactive androgens.
As for sex hormones, they differ: in women they are estrogens, in men they are androgens. The task of the latter is the growth, maturation, functioning of the reproductive system and the formation of secondary sexual characteristics. The task of estrogens is sexual arousal, the ability to bear and nurse a child and the performance of other functions of the female reproductive system.
What happens with hormonal failures?
Disruption of hormone production leads to very specific consequences. For example, with an overabundance of cortisol, a hormone associated with stress and metabolic regulation, Cushing's disease can develop. With the disease, obesity and muscle atrophy occur. In addition, women begin to grow a mustache or beard – this is due to the increased production of other hormones. Concomitant consequences of Cushing's disease are bone fragility up to osteoporosis, impaired insulin sensitivity and, as a result, the development of diabetes.
Another example is hypothyroidism, that is, insufficient hormone production, and hyperthyroidism – their overabundance. In the first case, anemia, cold intolerance, bradycardia, depression, brittle nails and brittle bones, puffiness of the body and other symptoms may occur. For children, this disease is dangerously high risk of developing cretinism. Hyperthyroidism (excessive thyroid gland activity) is associated with tachycardia, heat intolerance, increased appetite, accelerated metabolism and, as a consequence, excessive thinness and exophthalmos (bug-eyed).
Why is the hormonal norm relative?
It is widely believed that there is a certain hormonal background – the norm of hormone production, but this is not the case. Each person has an individual ratio of the amount of hormones at a certain age and under certain circumstances.
Have you ever heard the expression: "Children grow up in a dream"? It illustrates the fact that hormones can be produced in different amounts at different times of the day. In children, growth hormone is produced at night much more intensively than during the day. Therefore, it is possible to talk about the hormonal background only in the context of "here and now" and this particular person.
About the author: Olga Smirnova – Doctor of Biological Sciences, Professor of the Department of Human and Animal Physiology, Head of the Laboratory of Endocrinology of the Faculty of Biology of Lomonosov Moscow State University.
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