The technical term for baldness is alopecia, and cats are subject to a form of it, though a very different form than the human male-pattern baldness. Feline endocrine alopecia is probably hormone related (as is male-pattern baldness), but the areas where the hair thins are the posterior, underside of the tail, belly and inside of the thighs.
The remaining hairs can be easily pulled out, but the areas are never completely smooth. No pain is involved, but it does make the cat look less attractive. Some cases respond to hormone treatments. (There is no “Hair Club for Cats,” as far as we know.)