Could a human grow up larger by manipulating their endocrine system?
In my world there are a group of female warriors with an unusual ability: the resources of their bodies are fungible. For instance, they can make the muscles in one part of their bodies stronger at the cost of making another weaker, make an arm harder at the cost of making some other body part softer and so on. As the answers to this other question of mine indicate, using this ability effectively in a combat situation is tricky. However, it seems clear that being bigger and stronger at baseline would be an asset (indeed, even if the ability is useless in combat, being bigger and stronger is an asset in combat).
This leads me to wonder whether this "fungibility" ability (say that three times fast) could be used to achieve more height and stockier build, by rearranging the hormones produced by the body starting from the onset of puberty. My (admittedly pretty rough) knowledge of endocrinology and human development is that growth is triggered in part by hormones (notably human growth hormone or HGH), and thus a tweaking of hormone production could have some effect.
Specifically, women with this ability can, at will, change the amount of the various hormones produced in her body, subject to the constraint that she cannot increase overall hormone production through the ability itself, nor produce hormones beyond those normally created by a human female at a given age (so, producing hormones that trigger further hormone production is fair game in principle). To be clear, the idea here is that, given the current level of hormone production in the body at any particular instant, the person can trade, e.g. estrogen for HGH in equal quantities, but can't unilaterally increase HGH.
Assume for simplicity an otherwise normal 10 year-old human female, who has not yet entered puberty and the had the corresponding growth spurt, that they are genetically predisposed to grow up with an average height and build, and will have adequate nutrition to support their growth.
Given these assumptions, is it possible for a woman with this ability to grow larger than she might have by the time she reaches physical maturity? If so, what would be the most likely side effects?
Note that creation of extra muscle mass through this mechanism is not necessary (assume that they are committed enough to build necessary muscle through training and exercise).
This post was sourced from https://worldbuilding.stackexchange.com/q/140648. It is licensed under CC BY-SA 4.0.
1 answer
The two hormones that can change height in a growing prepubescent child are:
- Human growth hormone
- Testosterone
With HGH, it is often given to children who have Growth Hormone Deficiency or to children whose growth hormone production is normal but they are on a growth curve showing they will likely be much shorter than average. For example, girls with Turner's Syndrome (missing one X chromosome).
Does it work? Yes. But not as well as many would hope. Studies of children with normal GH production show an increase with HGH treatment of 1.5-3 inches. Now, 3" (7.6 cm) is pretty significant, but it's also not common. First of all, these children started off much shorter than average (usually well below the 3rd percentile on the growth by age charts for their gender). Second, it's not everybody.
Other studies show a similar gain, but note that "adult height gain of children with non-familial short stature were significantly higher than of familial short stature." This means that if the predicted original height was low due to genetics, the gain with HGH treatment is less.
Your characters will not need to pay for HGH treatment (really expensive) or take shots. They will not have any side effects that come from adjuncts to the treatment (old versions of HGH were sourced from the pituitary glands of cadavers; new ones are genetically engineered like insulin is).
About those side effects. Yep, there are plenty. Even in people with growth hormone deficiency who are taking it (as children or as adults) titrated such that they raise their GH levels (and IGF-1 and IGF-3) to normal or even just shy of normal will have side effects.
- Carpal tunnel syndrome
- Increased insulin resistance
- Swelling in the arms and legs (edema)
- Joint and muscle pain
- For men, enlargement of breast tissue (gynecomastia)
The other problem is which hormones will you use less of in order to increase the production of GH in your characters?
That's not super hard if you start at age 10. Just delay puberty. At that age, hormone production is ramping up. Bring it back to 8 or 9 year old levels and keep it there for a year or two longer than the girl's body would have done on its own. Delaying puberty for a short time isn't harmful in and of itself.
Of course, the shorter the time on the increased HGH, the less of a height gain you'll get.
The testosterone component has been done here. Check out How can genetic enchancements allow male and female sports leagues to intertwine with each other? While your question is not really a duplicate of that one, it overlaps a lot and the other question's answers discuss testosterone.
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