In her book Essentials in the Endocrine and Reproductive System , Madeleine Debuse defines them as “chemicals produced by the body that control numerous bodily functions.” A description that shows how much hormones can cover. In the words of the researcher Luis Miguel García, from the Cajal Institute of the CSIC, in Madrid, they are “ chemical substances that, moving through the blood, communicate the cells of one organ with those of another ”. This expert on sex hormones, who studies their influence on something as far from the genitals as the brain, warns that the idea that they always come from a gland “has become outdated.” Today it is known that the organs that produce them are legion, from the brain to the fat cells of the whole body.
As for their mission, they are involved in mechanisms as different as growth, reproduction, memory and emotions, among many others. In fact, its global function is to coordinate the activity of the cells of different organs and maintain homeostatic balance , that is, to ensure that all vital parameters are kept within a series of constants and that we are healthy.
However, for a hormone to send a message to a cell, there must be a receptor protein . If this fails, the cell does not receive the message and the consequences are generally disastrous for health. The same happens if something does not go well in its production, as in diabetes. Fortunately, since the physiologist William Bayliss 1 introduced the term hormone in 1902, after the discovery of one of them, secretin, it was soon seen that the artificial synthesis of these messengers could offer many advantages to the diseased organism. The starting gun was given by the German chemist Friedrich Stolz, who in 1904 manufactured the first synthetic hormone, adrenaline. Three years earlier, the American chemist Jokichi Takamine had managed to isolate it from adrenal gland secretions.
The first medical use of adrenaline was for asthma and bleeding control in surgery. Then, it was possible to synthesize thyroxine, which revolutionized the treatment of diseases such as cretinism and goiter. But if there is a hormone that has influenced medicine in a sustained way, it is insulin , since it was isolated by Frederick Banting and John Macleod in 1926. Its discovery, recognized with a Nobel Prize, allowed its isolation and purification from extracts of the pancreas of cows and pigs, to treat diabetes.
Currently, science is working with hormones as a possible solution to brain damage, obesity or heart damage. The idea of using them to make the elixir of happiness is even cherished. What we know about them is only a shadow of all that remains to be found out. Therefore, his study is far from finished.
For one of the multiple chemical messengers in the body to be defined as a hormone, it is a necessary condition that it uses the blood conduit to communicate different organs. Hence, there is some controversy about whether or not some neurotransmitters – whose main function is to carry messages between neurons, all in the brain – are hormones. With dopamine, there is no question. In addition to its important role as a neurotransmitter, it travels through the blood from the adrenal glands to different parts of the body . And those long journeys also correspond to its multiple functions. But it is its role in emotions that has attracted the most attention from scientists in recent years. An experiment reported in Nature Neuroscience demonstrated how listening to music that we like triggers dopamine secretion. The same goes for the feeling of being in love.
Another work, collected in Current Biology , affirms that it is responsible for our aspiring to pleasant goals, such as those trips that are far beyond our economic possibilities. That daydreaming prior to deciding how to spend your free time is, apparently, highly influenced by this hormone. Perhaps its relationship with pleasure explains its role in addictions . Most drugs cause dopamine levels to skyrocket, and when you try to quit, the monkey arrives, because the good feelings linked to this pleasure hormone are missed. The latest studies even point to social networks, such as Facebook and Twitter, as generators of this catecholamine.
In medicine, its role could be key to curing many more disorders, as it is associated with the placebo effect, which makes us overcome symptoms and diseases after taking, for example, a simple sugar pill. However, so far its best-known clinical application is in the treatment of Parkinson’s . Specifically, levodopa, the precursor of this hormone, delays the symptoms of a disease that remains incurable. Likewise, its use has been recorded for septic shock – an infection that degenerates into severe arterial hypotension – and some heart diseases. On the other hand, an article published in the journal PNAS has shown that the administration of dopamine in tumors increases the size and structure of the blood vessels that they use to feed themselves . This could facilitate the access to the malignant cells of the anticancer agents, something until now difficult. Since it has always been said that people with positive thoughts respond better to chemotherapy, the author of this study, Ohio State University oncologist Sujit Basu believes that the dopamine triggered by those thoughts may actually have had a biological effect on the tumor.
Sometimes a set of biochemical reactions lurks behind exaggerated weight loss or gain. When this occurs, it is due to poor regulation of thyroxine, the main hormone secreted by the thyroid gland, which is located under the walnut and above the windpipe . Its hyposecretion is responsible for slowing down metabolism, which can lead to weight gain, muscle weakness, increased sensitivity to cold, decreased heart rate, and a loss of alert mental activities. When it is secreted excessively, the equally undesirable effects are just the opposite.
Since Edward Kendall isolated the active principle of thyroxine, also known as T4, in 1914, it was used to treat diseases caused by delthyroid deficiencies . The most common are goiter – enlargement of the gland itself, which affects up to 60% of women over the age of sixty – and cretinism, a disease associated with delayed physical and mental development of the child. In the field of hormones, the possible indications for thyroxine continue to expand over the years. The New England Journal of Medicine rejected in a recent comment the screening of pregnant women in search of unbalanced levels of this hormone, since a study had proven that this had no influence on the IQ of future children, a possibility with which it is speculated.
Other work has ruled out that smoking influenced thyroid function and thyroxine production. Likewise, it has been proven that people who undergo dialysis and have problems with this hormone have a worse level of survival. Finally, a Spanish experiment, published in the European Journal of Clinical Investigation , bets on a risky and innovative thesis: it is not the deregulation of thyroxine and other thyroid hormones that causes changes in body weight. On the contrary, they are what modulate and determine hormonal levels. Ultimately, the research on T4 will still give a lot to talk about.
