Wikipedia says:
A "disease" or "medical condition" is an abnormal condition of an organism that impairs bodily functions, associated with specific symptoms and signs.
The key word is abnormal. If something is naturally common in humans, and doesn't impair any bodily functions, it shouldn't really count as a "disease". Like being short, as a matter of fact.
FDA has these views, as they only approve treatment of people with specific shortness-causing disorders, or within 1.2% of most extreme shortness (which is highly atypical). If people pursuing height expand this band to bottom 50% of current population, or bottom 80% of historical record, and redefine it as an illness, then it will be a lie, as a matter of fact.
Even better case is premature ejaculation, which is estimated to "affect" 30%-70% of American males. It doesn't impair any bodily functions. So it's factually incorrect to claim it's an illness.
Re: premature ejaculation, see The sooner the better. There is excellent therapy for those who desire it, but ironically the SSRI's that work so effectively to delay ejaculation were developed to treat depression, for which their effectiveness is the same as placebo. Yet, they are FDA-approved for treatment of the latter, not the former.
There was some talk here about height taxes, but there's a better solution - redefine shortness as a treatable condition and use HGH to cure it. They even got FDA on board with that, at least for 1.2% shortest people.
Unsatisfactory sexual performance became a treatable condition with Viagra. Depression and hyperactivity became treatable conditions with SSRIs. Being ugly is already almost considered a treatable condition, at least one can get that impression from cosmetic surgery ads. Being overweight is universally considered an illness, even though we don't have too many effective treatment options (surgery is unpopular, and effective drugs like fen-phen and ECA are not officially prescribed any more). If we ever figure out how to increase IQ, you can be certain low IQ will be considered a treatable condition too. Almost everything undesirable gets redefined as an illness as soon as an effective way to fix it is developed.
I welcome these changes. Yes, redefining large parts of normal human variability as illness is a lie, but if that's what society needs to work around its taboos against human enhancement, so be it.