Great Teacher Onizuka

Precocious Puberty

            Yes, it is finally happening, anime science 101 will be delving into the biology and science behind puberty.  Anyone looking for racy humor or 18+ material will be sadly disappointed as I will be keeping things above the board for this and any future posts.

            Great Teacher Onizuka or GTO is a comedy/drama that came out in 1997 and focuses on the journey of Eikichi Onizuka as he strives to become the greatest teacher ever.  I began rewatching it recently and while there isn’t much in the way of science, to dissect it does tangentially bring up an interesting topic, that is not often covered in anime puberty.

Great Teacher Onizuka

            What makes Tomoko Nomura different from a lot of other anime girls is that she is completely human in a normal everyday setting and we are informed by Tomoko herself when puberty began.  This makes her perfect for discussing precocious puberty.  When we meet Tomoko, she is a 9th grader, which is actually part of junior high in the Japanese educational system.  Our resident teacher with questionable tact is told by Tomoko when she began puberty during one of the early episodes.

            As it turns Tomoko Nomura began going through puberty in the 4th grade, which may shock the viewer given how surprised Onizuka was when he found out.  However, is that really so abnormal, to begin puberty in the 4th grade?

Tanner Stages

            The Tanner stages is a physical development scale that is used to measure the physical development of children, teenagers, and adults.  Specifically, it looks at the size and development of primary and secondary sexual characteristics in men and women.  The age and speed at which individuals reach and pass the different stages of the scale varies quite a bit, but it is still a good way to discuss the onset of puberty.  There are five stages in the scale and I have simplified the definitions for brevity and to keep this post at a level available to all ages.

Tanner I- usually age 10 and under

Tanner II– usually age 10 to 11.5

Tanner III- usually age 11.5 to 13

Tanner IV- usually age 13 to 15

Tanner V- usually around age 15 or older

            One way to mark the start of puberty is with the beginning of Tanner stage 2, which does vary by country, and according to a 1993 study begins at the age of 10 in Japanese females.  Interestingly, that is almost a year earlier than Switzerland, where the age is 10.9.  A Japanese 4th grader will typically start the year at the age of 9 and finish at the age of 10, so beginning to go through puberty in 4th grade isn’t all that abnormal.  The question that still remains is why would GTO tell the viewer the age at which Tomoko’s began to go through puberty?

            While it has gotten more press in recent years, scientists and doctors have known for some time that the average age at which puberty is beginning in both men and women has been decreasing for some time.  I would like to think that Tooru Fujisawa is trying to make some sort of statement about this, but I think I am giving him too much credit.  Now you might be wondering why I am even bothering to talk about this then, and that is precocious puberty, even if it didn’t happen to Tomoko.

Precocious Puberty

            What exactly is precocious puberty?  It is when puberty starts too early, which is defined as being 2.5 standard deviations below the average age.  This can be measured by the beginning of Tanner stage 2, or the onset of menstruation.  A 1993 study found that the average age of Tanner stage 2 in Japanese girls occurs at 10 years old (standard deviation plus or minus 1.4).  I know the study is 25 years old at this point, but it is still relevant because: A- it was the only one I could find, and B- GTO was written only 4 years later in 1997.  This means the study results would be similar to what Tooru Fujisawa would have seen when writing GTO.

            This means that a Japanese girl at the time of GTO would have to be in Tanner stage 2 at the age of 6.5 years old to qualify for precocious puberty.  The mean age of Tanner stage 2 minus the standard deviation of the study times 2.5.

10 – (1.4×2.5) = 6.5

            Even if we assume that Tomoko entered Tanner stage 2 at the beginning of 4th grade when she was 9 years old, she still wouldn’t have precocious puberty.  Komoe Harumachi from Eiken Club is probably a better example given that human cells can only replicate once every 24 hours, and that is only in certain situations, Komoe must have begun developing several years before this point, making her much more likely to have precocious puberty.

Causes of Precocious Puberty

            The causes of Precocious Puberty can be broken down into 2 groups, central and peripheral.  Central refers to a cause that can be directly linked back to problems with the pituitary and/or hypothalamus, which end up producing more sex hormones than normal, jump-starting puberty.

Disease- Langerhans cell histiocytosis

Genetic conditions- McCune–Albright syndrome

Cancer- Tuber cinereum hamartoma,

Brain Damage- focusing on the pituitary and hypothalimus

            Peripheral causes of precocious puberty come from outside of the brain, and all of them result in the body’s being exposed to more estrogen and other sex hormones than normal, jump-starting puberty.  Some times the exposure can come from non-brain tumors which produce sex hormones or precursors of sex hormones.


Adrenal tumors

Germ cell tumor

Congenital adrenal hyperplasia

            Another source of sex hormones is the environment and exposure to these hormones can cause puberty to start earlier than it should.

Exogenous hormones

Environmental exogenous hormones

As treatment for another condition

            There are also several risk factors that can contribute to precocious puberty:

Female- girls are much more likely to go through precocious puberty

Being African American

Obesity- it is thought that body fat percentage is one of the triggers for the onset of puberty, and being obese signals the body that it is ready for reproduction and puberty.

Radiation– Radiation treatment for central nervous system tumors can increase the risk due to damaging the nervous system

Problems of Precocious Puberty

            Just to be clear: precocious puberty is not physically harmful to the individual going through it, beyond being shorter than average.  This is due to puberty’s beginning and ending sooner than usual, robbing the individual of several years of height growth.  So other than being a little on the short side, what is the big deal about precocious puberty?  There is actually a rather large deal surrounding precocious puberty and we can see that in Tomoko Nomura.  Tomoko Nomura is the subject of ridicule from the entire class, including her former best friends.

            During first the quarter of the show or so we see Tomoko Nomura being ostracized and bullied.  This has impacted her to the point where she is found playing kids games by herself, having little interest in much of anything.

Paper being thrown at her during class

Tomoko Nomura

Playing with dolls by herself in the park

Tomoko Nomura


Tomoko Nomura


            There is actually a treatment for precocious puberty and that involves treating the underlying condition that causes early puberty, which can include surgery, medication, and diet.  Additionally, doctors can prescribe hormones that actually block puberty from progressing until the child is at the appropriate age.  After the hormone treatment is stopped, it takes about 16 months for normal puberty to resume.  Some degree of counseling is also recommended given the bullying and other issues that can occur as a result of the condition as seen with Tomoko.


            While Tomoko Nomura clearly does not have precocious puberty, she was still bullied as a result of her development.  Her character is, however, a good example of what can happen to girls who begin puberty a little early.  A better physical example of extreme early development is Komoe Harumachi from Eiken Club.


Author: Anime Science 101 is an American science teacher with eight years of experience working in high school and middle school classrooms. His last teaching job was overseas in Mongolia, where he had easy access to the home islands of Japan, which went to twice for a total of 9 weeks spent travelling the country. While his main background is Biology, specifically all things related to medicine due to two years of medical school, he can teach all aspects of science, including anime science.

5 thoughts

  1. I’ve recently watched those two episodes and I started to think there was an underlying condition. Tomoko is made fun of for being not too cognitive at times but I think something is going on mentally, as in a disorder or illness of some sort… idk just something I thought about

  2. I did quite a bit of substitute teaching in between jobs. Mostly K-6 classes in my most recent go-round. It is a very stress filled position.

    I rarely noted any visible signs of puberty in 4th grade. In 5th grade, there might be a couple of girls who were clearly beginning to develop. By 6th grade, it was half the female students. *Nobody* was developed like 6th grade girls in anime and I think that is just a fantasy that boys (and some men) have.

    6th grade was when the boys really started showing signs of puberty. By 8th grade, all the boys had kicked into their growth spurt.

    So, in general, the girls had a 2-year head start on the boys and were the taller group (as an average) in 7th grade. Menarche in girls does seem to be happening a year earlier than in medieval times, probably due to improved nutrition and greatly reduced physical labor. There are no comparable records for boys.

    My own puberty started in 5th grade. I was a very early starter. Started getting zits, started getting taller, and started getting really horny. It was NOT a fun time.

    1. I am glad you liked the post and as a teacher I feel your pain. However, I teach HS which is a world of difference from k-6. Your comments on the two year head start and one of the reasons for it are correct. Early puberty is also an issue in boys, but is somewhat under reported for pretty obvious reasons. Also when it comes to precosious puberty it is about 4 times more likely in girls than boys.

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