As people progress from childhood to adulthood, they go through a stage called adolescence. Adolescence is a period of major social, environmental and biological change in a person’s life. The onset of puberty, which usually occurs in the youth years, is an important period of human physical and emotional development. In addition to the more pronounced bodily changes that occur during this time, an adolescent’s brain also goes through unseen changes. These changes are driven by chemicals called hormones.
Hormones help the body grow taller, change shape and even hair growth. Although hormones act on different parts of the body (such as bones, muscles, or skin), several important hormones are produced in the brain for puberty. Scientists are learning more about how hormones affect how the brain grows and changes.
Whether a boy or a girl, his body starts to change from the moment he is born and continues to change as he gets older. This is a process called human development. One can think of human development as they go through several important stages of life such as infancy (0-2 years), childhood (3-11 years), adolescence.
While the age of 12-18 is adolescence, the age of 18-24 is called young adulthood. As you can imagine, there are many variations from infancy to young adulthood! Understanding these changes and how they happen can help a person better understand himself and those around him as he matures.
Hormones and the Body
So how does the body know it’s time to grow? What affects this change inside and outside in this process? This adolescent period of development and change is a highly complex process and usually requires an organized system to manage all moving parts. For example, many different instruments need to play the right notes at the right time to produce the beautiful music that is heard when a symphony is heard. In order for all these separate elements to work together, a chef tells each instrument what, when and how to play.
The genes in the body are like musical notes strung together to make each body its own unique song. When the appropriate time comes, special chemicals called hormones are secreted. Chemicals made in one part of the body (an endocrine gland) that then travel through the blood to tell other parts of the body what to do are called hormones. These are like conductors telling other parts of the body what to do. Many organ systems in the body, then, are like tools that follow the orders of the chief and bring the whole process to life.
During these complex transition periods, hormones circulate throughout the body and serve as messengers to grow (or stop growing), change shape and size, or do more (or less) than what the body needs, and there are about 50 different types of hormones in the human body. .
Some, like adrenaline and cortisol, help us react to stress and initiate the “fight or flight” response. Others, like melatonin, help adjust our biological clocks and tell us when to sleep or wake up. Many like thyroxine and insulin help control metabolism. Others, such as estrogen, testosterone, and growth hormone, are critical for the changes that occur in our body as we develop during puberty, such as the growth of the reproductive organs.
What Happens During Adolescence?
Adolescence is the transition from childhood to adulthood and is named after a series of hormone-induced changes in the body just before and during puberty. The shape, size, and composition of the body change as an organism progresses towards sexual maturity, which is the ability to reproduce. Mood and behavior also change as a result of puberty. The same hormones that cause changes in the body also help shape the structure and organization of the brain. During adolescence, our brains strengthen and fine-tune connections that allow for mature ways of thinking, feeling, and behaving.
Early in puberty, the adrenal glands (located above the kidneys) produce hormones called androgens such as DHEA (green). You can see the earliest signs of puberty such as pubic hair, body odor, oily skin and acne at this stage. Next, two small brain areas called the hypothalamus and the pituitary gland (pink) send messages to the reproductive organs, telling them to make sex steroids such as testosterone, estrogen, and progesterone (blue). These hormones can shape the structure of the brain and function throughout development.
Androgens are hormones made by the adrenal glands (men and women), testicles (men only) and ovaries (women only) that regulate the growth of hair, bones, and the male reproductive system. They are a group of hormones often associated with male characteristics, but they are also crucial to the proper development of females. While men experience a large increase in androgen testosterone during puberty, testosterone also increases in women, but less than men. As a result, while the brain circuits are organized in gender-specific ways, it makes the brains of women and men slightly different. This includes differences in growth, survival, and cell type in various brain regions. There are these subtle differences called sexual dimorphism. These differences;
It is a biological feature that differs in males and females belonging to the same species, such as the lion’s mane (only males) or the kangaroo pouch (females only). This is provided by another group of hormones called sex steroids as the brain prepares for the unique biological demands of both sexes. There is another group of hormones made from cholesterol that control the differences between male and female sexual development during puberty. It is produced by the ovaries in women and the testis in men and promotes the development of secondary sex characteristics. Appearance changes, which are different in men and women and symbolize the completion of sexual development, occur due to increased sex hormones during adolescence.
For girls, this includes wider hips, bigger breasts, and the onset of menstruation. For men, this includes increased muscle mass, a deeper voice, and growth of facial hair. A rapid rise in height, called a growth spurt, usually accompanies puberty in boys and girls. Steroid hormones also activate the brain circuits involved in sexual behavior, so adolescents increase their interest in sex.
Adolescence and Its Effects on the Brain
On average, puberty occurs between the ages of 10-14 in girls and between the ages of 12-16 in boys. There are many differences in the timing of adolescence between individuals. Scientists have discovered that the onset, duration, and pace of puberty can be influenced by factors such as a person’s cultural background, education level, body composition, and genes. Interestingly, the average age at which puberty starts has declined over the generations. The ability to accurately and reliably measure changes that occur in the early stages of adolescence is an important step in understanding how adolescence affects the brain.
One way scientists can study the effects of hormones on the brain is to study animals such as rats. Using animals, he can better control environmental factors such as diet and conduct experiments that are impossible to perform on humans. We can remove body parts (such as testicles or ovaries) where hormones are produced and examine how development proceeds without these hormones. It can use chemicals to trigger puberty and monitor the growth of certain neurons. And because mice have a shorter lifespan than humans, they can study puberty in weeks rather than years. The biological mechanisms of animals, such as puberty, provide information at a level of detail that is not possible otherwise.
Still, there are large differences between humans and other species, so what happens in mice cannot be considered exactly the same as what happens in humans. A person’s hormones cannot be changed for research because they can have a long-lasting effect on the person. Instead, to study humans, researchers measure things that already occur naturally in the body, such as the amount of testosterone in the blood or the age in the first menstrual cycle. Scientists can then test whether these bodily changes are linked to other body measurements such as brain volume. These links cannot tell us whether one thing leads to another, they just tell us that they are related in some way.
How Pubertal Hormones Change Brain Structure and Function
Adolescence is a dynamic transition period that prepares us for the adult world. Yet even as adults, life is in constant flux, and the brain needs ways to adapt to these ongoing changes. The same hormones that help shape the brain and body during adolescence are actually at play all life! Even before birth, testosterone and estrogen play a role in early brain development, helping to create new neurons and guide them in building the structure of the brain. During adolescence, these hormones act to transform the organization and structure of the brain into its permanently mature form.
Androgen hormones such as testosterone and DHEA as well as estrogen hormones such as estradiol are particularly important for the proper development of parts of the brain involved in learning and memory, sexual behavior and emotion processing. Scientists are beginning to get a better picture of how pubertal hormones alter the structure and function of the brain, using animal models with studies of hormonal disorders as well as healthy people.
There are several ways to change brain structure. One of these is neuron growth or death that alters the overall size of brain regions. In animals and healthy humans, pubertal hormones are essential for the proper growth of brain structures such as the hypothalamus, pituitary gland, and amygdala. Because the hypothalamus and pituitary gland are crucial for lifelong hormone regulation, improper growth of these brain regions during puberty can lead to long-term health consequences such as sleep or metabolism disorders. Klinefelter syndrome, a genetic disorder caused by an extra X chromosome, leads to testosterone deficiency and significantly reduced amygdala volume during puberty. These hormonal and brain structure changes can contribute to the social and emotional problems these individuals face.
Another way to change brain structure is to change the number of connections each neuron makes with other neurons, which alters the overall complexity of the brain circuits. For example, there are many hormone receptors for the estrogen hormone in the hippocampus, and estrogen has been shown to increase the number of connections between neurons in rats. The increasing number of neuronal connections in the hippocampus may have implications for improvements in learning and memory that are often seen during adolescence. Sex steroids play a critical role in myelination in animals and humans
A type of insulation that covers neurons in a substance called myelin so they can quickly carry information to other neurons at a distance. This is a process that isolates the brain’s neurons to make electrical signals more efficient. The fact that myelinization occurs in adolescence has determined us that efficient communication between brain regions helps to process information quickly and is a necessary part of the maturation process of the brain.
Author: Ozlem Guvenc Agaoglu