Actually, Aldous Huxley's brother Julian beat him to the punch.
For two days we were marched through pleasant park-like country, with villages at intervals. Every now and then some new monstrosity in the shape of a dwarf or an incredibly fat woman or a two-headed animal would be visible, until I thought I had stumbled on the original source of supply of circus freaks.
In Huxley's 1926 novella "The Tissue-Culture King", a certain biological researcher named Hascombe was trekking in the African jungle when he stumbled across the the realm of King Mgobe.
The narrator is captured about fifteen years later, by which time Hascombe has created a whole religion around cell cultures of the King, at first a fad, then a subscription model where any self-respecting subject had to have a culture of the King's cells.
By the close of the third year there was hardly a family in the country which did not possess at least one sacred culture. To be without one would have been like being without one's trousers--or at least without one's hat--on Fifth Avenue.
And then, Hascombe gets the idea of modifying humans :
The first thing was to show Bugala how, by repeated injections of pre-pituitary, I could make an ordinary baby grow up into a giant. This pleased him, and he introduced the idea of a sacred bodyguard, all of really gigantic stature, quite overshadowing Frederick's Grenadiers.
My God, what a crowd! I was getting used to giants by this time, but here was a regular Barnum and Bailey show; more semidwarfs; others like them but more so--one could not tell whether the creatures were precociously mature children or horribly stunted adults; others portentously fat, with arms like sooty legs of mutton, and rolls and volutes of fat crisping out of their steatopygous posteriors; still others precociously senile and wizened, others hateful and imbecile in looks.
Hascombe manipulates animal embryos to produce monstrosities for the consumer market:
Then we passed to the next laboratory, which was full of the most incredible animal monstrosities. This laboratory is the most amusing," said Hascombe. "Its official title is 'Home of the Living Fetishes.' Here again I have simply taken a prevalent trait of the populace, and used it as a peg on which to hang research. I told you that they always had a fancy for the grotesque in animals, and used the most bizarre forms, in the shape of little clay or ivory statuettes, for fetishes.
I thought I would see whether art could not improve upon nature, and set myself to recall my experimental embryology. I use only the simplest methods. I utilize the plasticity of the earliest stages to give double-headed and cyclopean monsters. That was, of course, done years ago in newts by Spemann and fish by Stockard; and I have merely applied the mass-production methods of Mr. Ford to their results.
There's a lot more about telepathy (plus the introduction of the tinfoil hat), but this "Heart of Darkness" meets The Island of Doctor Moreau story appears to contain what you're looking for.