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Forum Name: Endocrinology Topics

Question: Gigantism attributed hormones


 timfwheeler - Wed May 02, 2007 1:12 am

This was asked on a test recently, and I had a dispute with the answer the professor chose, and searched alot of medical journals and the closest information that I found was that it could not be determined one way or another, supporting my origional answer. I asked her to support her evidence and she refused to. Nothing in the required text for class or the lecture supported her answer. Before bringing this to the head of the department, I wanted the opinion of someone who knew more than I did on the topic. This was the question:
A 10 y/o girl is 6 feet tall. Her father is 5'8, and her mother is 5'0. What could be attributed to the girls height at her age?
A. High human growth hormone
B. High estrogen
C. Low insulin
D. Low thyroid
E. A and B.
Some thoughts to concider, 1. We did not discus normal vs high levels of estrogen and its effects on bone growth or alterations in growth velocity, but sex hormones were discussed and said to attribute to a puberty growth spurt (but the growth spurt length was not discussed). 2. We did not discuss what is concidered normal age to enter puberty. 3. We did discuss that in an enviroment where there is no estrogen, bones continue to grow, and that estrogen treatment is required to cause the epiphyseal plates to stop growing. 4. Estrogen insensitivity was discussed and was suggested to have normal puberty increases in velocity, but increased expected height. 5. Early estrogen was said to cause sooner proliferation exaution of chondrocytes in epiphyseal plates, and to decrease expected height, but to increase height relative to age. 6. Growth hormone without estrogen or androgens was not discussed, or its effects on growth without androgens or estrogen. 7. Estrogen and androgen was only said to increase growth hormone output. 8. It was discussed that growth was linear untill puberty, which would cause a short burst in height then it would be stopped by the introduction of sex hormones.

My answer was A, high human growth hormone.
I answered this because only high growth hormone could cause the girl to be that tall concidering her parents (assuming that the parents did not have celiacs or lactose intolerance or nutritional deficencies during growth) which would be the only thing that would attribute the height. While normal amounts of estrogen and other hormones MAY add to the effects in this case, this is unknown in gigantism (if high or normal or low or no estrogen can or ever would effect growth velocity in someone with growth hormone levels high enough to cause gigantism), and it is possible HIGH estrogen would cause early epiphyseal closure, and likely if estrogen was increased proportionally with growth hormone that she would just reach her expected height (dad -13cm +mom)/2 + or -2 sooner. High levels of growth hormone have been shown to cause early puberty in people during high growth hormone treatment, so the estrogen SHOULD be normal for and adult or for puberty in the girl, and thus high would not be a factor, rather the growth hormone would take over and drive this train wreck. Additionaly, studies have showed that injections of high levels of growth hormone likely DO NOT add benifit in predicting height UNLESS they are given BEFORE puberty. The effects of high estrogen with or without growth hormone was not discussed in class, so that question shouldnt have even been asked in that manner, but rather in an essay.

Her answer was E. I layed out everything I said on this post to her during lecture, which she agreed with everything I said. All she said is that estrogen protects chondrocytes and high levels sould cause a growth spurt, adding additional height to her.

Remember, high levels of estrogen and its role was never discussed in class, and estrogen was only said to have a protective effect in chondrocytes that were not associated with height, but with appositional growth. The only thing estrogen was shown to do normally was cause increased rate of cellular turn over and increasing the rate at wich bone high was stopped.

The only thing that i can find even close to estrogen in chondrocytes was a study in rats with a estrogen producing mutation directly in the bones, limiting the exposure to normal androgens (now, there will be a greater level of estrogen to androgens in the model, and I have heard that rats do not stop growth at puberty like humans, but rabbits do, and the study with rabits showed that high estrogen given by pellets, not oral estrogen, WITH high growth hormone killed velocity of growth in length and sealed the bones in a few days)

Anyones thoughts would be appreciated
 Dr. Chan Lowe - Wed May 02, 2007 1:26 am

User avatar I would tend to agree with your answer for a few reasons.

You are correct that increased growth hormone (GH) would stimulate growth in height. GH stimulates a release in insulin-like growth factor-1 (IGF-1) that induceds bone and msucle growth.

Elevated levels of estrogen will induce early pubertal changes and thus induce the growth spurt earlier; however, it also induces bone maturation (i.e. closure of the growth plates of the bones). So, girls with elevated estrogen and subsequently early puberty do get their growth spurt early and tend to be the taller girls in their class initially but subsequently stop growing while the other girls continue to grow. Thus, the early estrogen girls end up shorter than expected.

The reason for this is that puberty induces a growth spurt that is essentially for a fixed amount of time. Once this time is up, the growth plates have fused and growth basically stops. The more time a girl has to grow before the growth spurt the taller she will be in the end.

So your professor is correct that elevated estrogen does induce growth; however, for the estrogen to induce enough growth to cause a 10 year old to be 6 ft. tall would be extremely rare. I'm not aware of any such cases. As an aside, girls who go through early puberty usually end up being less than 5' 4" (approx.) tall also arguing against a resulting 6' tall girl. (5'4" is considered the average height for an adult woman.)

Interesting question. Best wishes.
 timfwheeler - Wed May 02, 2007 7:13 am

Thank you for your review of this and response Dr. Chan Lowe, I really appreciate this.

Only one thing that I am not certain of is if the combination of high levels of human growth hormone (enough to cause a 10 y/o to be 6') would have and added effects from high levels of estrogen vs normal levels.

One thought is that puberty is related to high levels of sex hormones AND growth hormone.

Low levels of IGF would cause short stature during puberty (pygme {sp?} of africa for example)

That in mind, the only thing that I ever found on administration of high levels of HGH that caused any additional height was prior to puberty, and the general consensus was that administration of high levels of HGH during that time would cause no additional benifit.

So, would abnormally high levels of growth hormone get ANY benifit from EXTRA estrogen above that seen in puberty?

A study done in rabbits recently showed that high estrogen with high growth hormone only caused a decceleration of growth velocity and epiphyseal closure vs high growth hormone.

My instinct is that the estrogen would not add a benifit in high levels vs normal in a case where high hgh was already there and also that estrogen normally induces high growth velocity because of its ability to increase hgh and igf levels, but if they were already high any increase of estrogen above normal levels wouldnt make a significant difference.

Anyone agree or disagree?
 timfwheeler - Wed May 02, 2007 3:24 pm

After searching for several hours, I found an article that resolves this question.

"Role of oestrogen in the regulation of bone turnover at the menarche."

http://joe.endocrinology-journals.org/cgi/content/full/185/2/223

Basically the highlights of this shows that ONLY low estrogen induces increased change in bone growth in height, and includes refrences in females with turners and normal females and high dosages do decrease that rate of change. The article also shows the puberty growth spurt with high levels of hormones is more properly defined as a growth in width and weight.

So, according to the review, yes, growth hormone levels would make her tall, and high estrogen would silence the effects of the growth hormone, and only decrease the rate of change in verticle growth, and not increase it.

So the answer should be A. High Growth Hormone
 Dr. Chan Lowe - Thu May 03, 2007 2:00 am

User avatar Strong work in finding your answer.

Regarding your question about GH after puberty, once the growth plates are closed, long bone growth basically stops (except for a very slight increase that may occur but nothing like the rapid growth of puberty). After the growth plates are fused, giving growth hormone will not result in a significant increase in height.

Best wishes.

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