Could we make permenent kittens & puppies with high doses of estrogen?

Factual Questions
1

Please note this isn’t a question of ethics, just possibility. I’m not interested in a debate about the shoulds here, just the coulds.

Last night as I was trying to sleep I puzzled over “The Ashley Treatment” (growth attenuation) given to a handful of children with profound intellectual disabilities. The treatment, which in girls includes a hysterectomy, keeps them small forever. What I couldn’t figure out is how that works given that we spay and neuter young animals all the time, and it doesn’t make them stay small. Sometimes they even grow larger than their unaltered brethren, like oxen do.

So I looked up the particulars and the piece I was missing was that both girls and boys undergoing this treatment are given high doses of estrogen to make their growth plates close faster. This is where it differs from what we do to puppies and kittens.

But what if we did? If we subjected 7-14 week old puppies and kittens to both spaying/neuter and high doses of estrogen could we create cats and dogs that were smaller than usual for their particular breed? Ashley is reported to be 20% shorter than she’d be if they hadn’t done the treatment, but they waited until she was 6.5 years old. Would a kitten on the lowest end of when neutering is done be even more than 20% smaller than he’d be otherwise as a full-grown cat?

Would a treated kitten maintain the large eye-to-face ratio that young kittens possess? Would a treated puppy stay fluffy-coated?

Would it affect their lifespan? The effects of too much estrogen in women just sound unpleasant, not life threatening, though I’m obviously unsure about how this would play out in dogs and cats.

2

Remove the thyroid gland at birth. Congenital cretinism (hypothyroidism) creates a small individual, stunted physically as well as mentally.

3

We’ve already done this to an extent via selective breeding. Small lap dogs like the Cavalier King Charles Spaniel are bred to have puppy-like traits as an adult (big eyes, domed forehead and so on).

What we cannot do is maintain the “childish” personalities of puppies and kittens. Their bodies may remain small but their minds become adult.

4

Actually, we can. A large part of the process of domestication (even for big, macho breeds like rotweillers and huskies) was in selectively breeding for puppy-like personality traits, and in the process we ended up getting puppy-like physical traits as well. This is also true of cats, though to a lesser degree since we haven’t felt as the need to modify cats as much from their natural state.

5

The church in the late renaissance experimented with something similar - google “castrati”. Apparently it didn’t stop the growth phase, but did result in the voice not changing. To some extent this practice persisted, and I recall reading that there is actually a recording of one of the last of castrati from not long after 1900.

I guess the question is - is there one “growth hormone” or are there a mixed bag of signals from the body, so removing a few but not all can have interesting mixed effects.