↑ Вгору

Реферат на тему

Impact of evolution on human thought Testosterone


читати

Переглянути реферат

зберегти

Скачати реферат

друкувати

Друкувати реферат

Farid Gazizov

Impact of evolution on human thought

Testosterone

For a long period of time humans could not answer the question of what
makes a man, a man, and a women, a women. As was recently found main
difference is not just in presence of genitals. Probably one will ask
why? The answer is that genitals themselves are indirect products of
another matter. The name of this matter is testosterone.

“Testosterone is a hormone that stimulates sexual development in male
human beings. It belongs to a family of hormones called androgens.
Primarily the testicles, a part of male sex glands, produce androgens.
The ovaries in females and the adrenal glands in both sexes also yield
small amounts of testosterone and other androgens (The world book
encyclopedia).”

In its earliest crucial functions, in developing embryo, testosterone
play the key role in telling the cells of the genetically male embryo to
develop as a male. It is amazing, but all human embryo begins as
females for the first few weeks of an embryo’s life, a small group of
cells have potential to develop either as ovaries or testes. About one
million of genes that are needed to direct the development of a human
being, one single gene (the “SRY” gene), which is carried on the Y
chromosome, is responsible for determining the sex of the embryo. If
the embryo’s cells contain the “SRY” gene, the embryo will develop
testes, which at some point and for a limited period of time early in
its development produce and release a big amount of testosterone. It
turn, testosterone then signal the cells of other parts of the embryo to
develop as a male.

As shown in the study by a Stanford research group namely testosterone
is responsible for formation of genitals. An experiment was held on
newborn female rats. They were injected with testosterone.
Surprisingly, but the female rats developed male genitals, and female
genitals began disappearing. Later “converted” female rats started
revealing purely male behavior, and they were fully aware of usage of
their “new” male genitals. The same experiment was performed with male
newborn rats. It is amazing, but their penises withered and later
completely disappeared. This experiment is not ethical to perform on
humans, but random facts suggest that all most the same can be done with
humans. For instance, in lesbian couple, butches (female that
represents male) use testosterone injections to develop male features
such as deep voice, facial hair and muscles (“The He Hormone,” Andrew
Syllivan)

In girls, the adrenal glands begin to produce testosterone earlier than
in boys. That’s is how and why girls mature earlier, as a rule, than
boys. It was testosterone that stimulated the growth of girls pubic
hair and underarm hair (there are testosterone receptors in the skin of
the pubic area and the skin of the underarm that are genetically
programmed to react to testosterone by producing hair). And
testosterone stimulated girls skin to produce more oil, contributing to

e oil, contributing to
the acne of girls early teenage years, but also to the healthy glow of
the skin and the shine of the hair.

The medical book Reproductive Endocrinology by Drs. Samuel Yen and
Rovert Jaffe, states; “Testosterone and other androgens have some
biological activity o virtually every tissue in the body.” Among the
most important functions listed are “anabolic actions, such as
stimulation of linear body growth, nitrogen retention, and muscular
development.” This statement means that testosterone works to keep the
cells of the body functioning efficiently, making the best use of
nourishment of growth and maintenance, and particularly contributing to
the health of bones and muscles.

Having knowledge of the way testosterone function in the body,
artificial testosterone injections can be used for variety of purposes.
One of the purposes of artificial use of testosterone is to stimulate
sex drive. The balance of this hormone is responsible for initiating
and maintaining the production of sperm from early puberty throughout
adulthood in male body. During childhood and adolescence, these
hormones are responsible for:

Growth of genitals

Depth of pitch of the voice, increase muscle mass, and growth of bones.

Appearance of the body and facial hair.

Overproduction of testosterone caused by testicular, adrenal, or
pituitary tumors in the young male may result in precocious puberty.
Overproduction of testosterone in females, caused by ovarian and adrenal
tumors, can result in muscessation of the menstrual cycle and excessive
growth of body hair. Level of testosterone are low before puberty; they
begin to increase at the onset of puberty and continue to increase
during adulthood. Production begins to diminish at about age of 40,
eventually dropping to about one-fifth of the peak level by age of 80
(“Hormone of desire,” Susan Rako). Scientifically established men’s
testosterone, level is at least ten times higher than any of the women.
According to the last available date, even male population accounts for
less than 50 percent of the world’s population, major part of violence
is perpetrated by men.

Currently many males use testosterone shots or gel for the purpose of
body-building. Testosterone shots trigger imbetterment of appetite and
muscles growth. Besides, testosterone can have effects on the function
of several brain areas. One additional surprising effect of
testosterone is that it can not only affect the function of the brain
but also its development and anatomy. Study in laboratory of Roger
Gorskis at the University of California, Los Angeles, has revealed that
the sex difference in the brain anatomy appears to be due to the
presence of male sex hormones at a certain stage of brain development in
male rats. Later work has shown a similar effect of testosterone at
other brain areas: for example, the spinal nerve cells that control the
muscles of the genital area are more numerous in male rats (cross
sections through the hypothalamus of a male and female rats (male,

ugh the hypothalamus of a male and female rats (male,
(thinner and longer)).

Below is a human life example how hormone level can influence human
health, and behavior brought by John K. Young in his book “Hormones;
molecular messenger.”

“Bridget was divorcing Bob, her husband of tem years, so she was not
terribly surprised when she started to feel anxious and upset upon
awakening in the morning. She grew worried, however, when these anxiety
attacks became more frequent and stronger, coming upon her at all times
of the day. She went to see a psychiatrist. The doctor also assumed
the problem was stemming from her divorce proceedings and prescribed an
antidepressant. After two weeks of more anxiety and no relief coming
from the dedication, Bridget felt like committing herself to a
institution. Her nervousness was now even making her hair fall out; her
skin began to feel thin and bruised. She was not eating properly
either, but was surprised to see she had lost over twenty pounds.

One night Bridget’s best friend Virginia invited her to a dinner party.
Over the meal, someone mentioned how traumatic divorce was; Bridget
laughingly said that it was not making her thin and anxious, it was also
thinning out her skin and hair. One of the other guests, a young woman,
asked her to elaborate, and Bridget shyly told her the symptoms she had
been suffering from. The young woman then introduced herself as a
doctor. She asked Bridget to come down to her office for a few tests.
Bridget did and these tests revealed what the doctor had first
suspected; that Bridget was not suffering from a psychiatric disorder,
but rater a hormonal one. Her thyroid gland was overworking, giving her
the symptoms of thinning hair, thin skin, excessive weight loss, and
anxiety. Afte4r treatment all of Bridgets’ symptoms disappeared.”

The example described above suggests that level of testosterone
influence not only physical development of the body, but also is
responsible for emotions and behavior. One researcher, curios about
the fact that only male canaries sing during mating season, gave a
testosterone shot to female canaries. The result was amazing, the
female canaries “burst into song.” The same experiment was performed on
zebra finches. Dr. Christina Wang’s study reveals that men with low
testosterone level are irritable and aggressive than those with
high-normal level. “When their testosterone level was increased during
hormone-replacement therapy, their anger diminished and their sense of
well-being increased.”

Robert M. Sapolsy, in his book “The trouble with testosterone,” takes
opposite opinion side to scientists who think that increasing
testosterone level leads to changes in behavior (such as becoming more
aggressive). He holds an opinion that changes in surrounding
environment trigger change in the level of testosterone.

“Okay, suppose you note a correlation between levels of aggression and
levels of testosterone among these normal males. This could be because

his could be because
(a) testosterone elevates aggression; (b) aggression elevates
testosterone secretion; (c) neither cause the other. There is a huge
bias to assume opinion (a), while (b) is the answer. Study after study
has shown that when you examine testosterone levels when males are first
placed together in the social group testosterone levels predict nothing
about who is going to be aggressive. The subsequent behavioral
differences drive the hormonal changes, rather the other way around
(“Trouble with Testosterone,” pp. 152).”

It is a good point, but what about evidences suggesting that men after
taking testosterone injection find themselves more aggression than
normally. The article “The He Hormone” by Andrew Sullivan brings a good
example when a man after taking testosterone shot could not control his
increased aggressiveness and “had nearly gotten into the first public
brawl of his life.”

“Soon after I inject myself with testosterone I feel a deep surge of
energy. My attention span shortens. My wit is quicker, my mind is
faster, but my judgement is more impulsive.”

Several other studies suggest that individuals with winning attitudes
have higher testosterone levels, at least for a short period of time,
than those without such an attitude. One group of researchers, for
example, measured testosterone levels in six college tennis players and
found that testosterone levels began to rise in all of them before their
matches, apparently in anticipation of competition. The big surprise
came after the fact: the testosterone levels of those who won their
matches remained high, while the testosterone levels of those who lost
diminished.

A second group of researchers, at North Dakota State University in
Fargo, undertook even further step by trying to figure out if it was the
competition itself, or the mood produced by winning, that caused the
rise in testosterone. In their experiment, male college students either
won or lost $5 through a series of coin tosses. The task removed all
elements of skill or competition; blind luck determined winners and
losers. After the tosses had been finished, the researchers measured
the saliva of participants for changes in their testosterone levels.
Those who won money experienced a more positive mood and a rise in
“test”; those who lost whose a decrease in the later. The result
suggested that the acts of winning, rather than the nature of the
competition or the skill involved, improve mood and produces an increase
in testosterone levels. This experiment obviously supports Robert’s
Saporky statement that testosterone level changes with external factors.


Two more recent studies by a single group of researchers went further
to find out if one has to directly participate in competing in order to
experience increase in testosterone level. In the first study, the
researchers measured the salivary testosterone levels of fans who
attended a college basketball game. In another, they took the same

ame
measurement of a group who watched a World Cup soccer match on
television. In each study, testosterone levels were taken before and
after the game. In both experiments, those fans whose team had won
experienced a surge in their testosterone levels, while those fans whose
team had lost showed a drop.

The result was very surprising. Even the fans are not directly involved
in the competition, the their testosterone levels change in accordance
with whether their team is losing or winning. The supervisor of the
researches, a doctoral candidate in education psychology at the
University of Utah in Salt Lake City, makes a comment on the researches
notes: “Fans do not have much to do with outcome: there are more like
voyeurs to the team’s experience of competition.” Nonetheless,
experiencing victory even vicariously apparently has very real effect on
a person’s hormone levels.

Testosterone level is not only different among individuals, but it
changes within one organism one intraday basis. Testosterone level can
vary by up to fifty percent during one day. In the mornings it tends to
be higher than in the evenings. This is another reason why people feel
fresh in the mornings. During the day one might experience ups and downs
of testosterone level induced by winning mood effect. These up and
downs do not have effect on physical development of the individual (“The
Testosterone Syndrome,” Eugene Shippen, William Fryer).

Sensitivity to the changes in the testosterone levels is not very
researched subject. It is noticed that different individuals experience
different effects after having the same amount of testosterone injected.
The genetically determined differences in the numbers of testosterone
receptors may be one factor.

Besides stimulating growth of bones, body mass, facial hair, change in
voice, testosterone might be a possible reason of illnesses. In the
report by Paule A. Lotufo, Joann E. Manson, Alexandersen P, Haarbo J,
Christiansen C., on male pattern baldness and coronary heart disease,
the authors conclude that “vertex pattern baldness appears to be a
marker for increased risk if coronary heart disease. They state that
testosterone may provide a “plausible explanation for an association
between baldness and coronary heart disease.” The reference cited is a
study that shows elevated testosterone levels in men with prostate
cancer and baldness; however, these were no measured testosterone
concentrations in the data presented. Dr. Brian L.G. Morgan and Roberta
Morgan, in their book “Hormones,” are tying to link high testosterone
level with coronary heart disease. They bring into attention the fact
that in general, since women have lower testosterone levels than men,
according to available poll of data, they live longer lives. “Equal
numbers for both sexes are around by age thirty, and only 70 percent of
men reach age sixty-five, where as 84 percent of women do.”

On the contrary recent results from the Telecom Study showed that

hat
decreased testosterone levels were associated with increased
cardiovascular risk factors in otherwise healthy men.

Eugene Shippen and William Fryer, in their book “Testosterone syndrome,”
agree with the opinion that low level of testosterone are more
associated with increased cardiovascular risk factors, rather than all
the way around.

“The fundamental fact is this: a clear and ever-increasing majority of
medical studies report an association between high testosterone and low
cardiovascular disease in men. This is not a coincidental association,
since when testosterone is diminished well-accepted risk factors
increase, and when testosterone is administered in appropriate doses
most of the major risk factors for heart disease diminish. Moreover, in
the majority of patients, symptoms and objective EKG measurements
improve. These studies are confirming the results I have been getting
with patients for years. Men prosper health wise and live longer when
their testosterone levels are normal. Heart problems, in particular,
are more easily controlled (The Testosterone Syndromes, pp. 81).”

With growing old, men begin experiencing erective problems and losing
sexual interest. These problems are caused by diminishment in
testosterone level. Facts reveal that men who are taking testosterone,
in any form, experience surge of sexual interest, and overall
enhancement in physical strength. Eugene Shippen, and William Fryer, in
their book “The Testosterone Syndrome,” relate diminishing sexual
interest to a sign of future heart disease and diabetes, conditions
common in the male menopause (“The Testosterone Syndrome,” pp. 59)

At the end of this research, I would like to notice and bring example of
the fact that majority of scientific world hold opinion that artificial
testosterone if correctly applied can bring much of good to the human
kind, especially to elderly.

“Standford R. is seventy-four years old now, but he has had heart
problems since the early 1970s. It did not make life easy for him. He
is an athletic man who likes to hunt, fish on the river, and walk in the
woods. By the time Standford together with his chest pains, got into
the 1980s, it was time for a quintuple bypass. The chest pains started
up again in a few years later. His chest pains went away, his energy
returned and when he is not walking over the hills and fields and
hunting in the woods, Standford makes love. Sometimes twice a day (“The
Testosterone syndrome,” pp79).

Conclusion

As can be concluded from all researches discussed above change in
testosterone level triggers changes in behavioral pattern, and
environmental change followed by change in behavioral pattern triggers
change in testosterone level.

The arguments in scientific world regarding testosterone and their role
in human anatomy are not over yet. The subject is hard to explore,
because experiments that has to be done in order to find right answers
are not considered to be ethical on humans. The scientific world has no

scientific world has no
choice, but to use random historical facts to come to the answers.
However, the fact the testosterone play a huge role in human development
and behavior is not argued by any more.

Reference:

“The Testosterone Syndrome”; Eugene Shippen, M.D. and William Fryer, M.
Evans and Company, Inc., 1998

“Hormones; Molecular Messenger”; John K. Young, Franklin Watts, 1994

“The Trouble with Testosterone and other essays on the biology of the
human predicament”; Robert M. Sapolsky, Scribner, 1997

“The Hormone of Desire; The Truth about sexuality, menopause, and
testosterone”; Susan Rako, M.D., Harmony Books, 1996

“Never Too Buff”; John Cloud

“The He Hormone”; Andrew Sullivan

PAGE 1

PAGE 8


© 2013 Alive-inter.net Про сайт Зворотній зв`язок Відмова від відповідальності