Polysorbate 80?

Polyethylene sorbitan monooleate (Polysorbate 80) functions as an emulsifier, holding water and oils in suspension, in various foods and supplements. One vendor who sells this stuff says it fights DHT and "may help" hair growth. Yes, it may, but then again, it might not.
If you want a good head of hair, you need to start with a healthy scalp. Sebum (gook that comes out of your pores) can clog up your hair roots and cause all sorts of trouble for 'em, so what you want is something that will get rid of it. Detergent is what you need. Not just any detergent, you need something mild enough that it won't irritate your skin or hair. Just about every shampoo uses either sodium laurel sulfate or sodium laureth sulfate (or a combination of the two) as detergent.
A detergent molecule looks sorta like a pickle. One end is "hydrophilic" (grabs water molecules) and the other is "hydrophobic" (latches onto anything but water). The idea is to evenly distribute these molecules all over your head so they can work their way between the gunk on the hair and scalp. They can't just sell ya pure detergent 'cause it would be way too harsh . . . they mix it with mostly water (90 to 95% of your shampoo is water) and usually a bit of preservative, fragrance, conditioner, and sometimes a liquid form of plastic (the same stuff they put in hair spray) to give hair more "body." On top of that, they sometimes add glycerin (or some other chemical) so that it sticks to your hair after rinsing, and pulls water from the air into the hair shaft (usually in shampoo for dry hair). And they can add medication to combat dandruff or whatever.
. Anyway, when they mix something like glycerin, which doesn't mix with water, with the rest of the product, they have to add an emulsifier (in this case, polysorbate 80) so they can get the glycerin and other oil based goodies to stay mixed in with the water and not seperate. Like all good snake-oil salesmen, the folks who sell you shampoo are pretty good at making it seem better than what it really is. And sometimes they add some pretty weird stuff--like Tea Tree oil, which is rather irratiting to the skin and hair, and useless stuff like wheat germ oil or peach extract. Read the contents on an expensive bottle of shampoo and you'll see all sorts of useless stuff--sort of like mixing an exotic herbal tea in with the detergent.
. If you have thinning hair, you'll want to be using a clear (usually has some color to it, but it's transparent) shampoo. Doesn't have to be fancy. Just the basic sodium laureth sulfate (which is a tad easier on the hair shaft), water, and a bit of preservative is all you really need. Some off-brand baby shampoo would be just fine. This clear shampoo is particularly suitable for thinning hair because it rinses off better than the creamy shampoos, and won't leave a coating of hair goo to clog up the hair follicules and cause problems.
. So . . . Clear shampoo for thinning hair. The cheap stuff is fine, sodium laureth sulfate is a bit better than soduim laurel sulfate.
. No if you hair is thicker, you can use clear shampoo just fine. But if if it's limp or dry or damaged or whatever, wants to go its own way, you can use a creamy shampoo, which will leave a coating of various types on your hair shaft. As I mentioned, there are hydrating chemicals (glycerin) that put water into the hair, and liquid plastics that coat the hair and make it (1) seem thicker (2) shinier (3) keep it in place. They put all sorts of chemicals in, some actually work pretty well . . . a silicone oil like dimethicone is pretty good for detangling longer hair and making it appear less dull.
. So . . . to make a long story short, use a transparent shampoo for thinning hair, and use a creamy shampoo (with whatever extra conditioners, hydraters, detanglers you may need) for everything else. And no, polysorbate 80 doesn't have much effect one way or the other on your hair--it's primarily in the shampoo so that everything else will stay mixed.
. I suppose this is more than what you wanted to know, but I gave you the "reader's digest" version . . . learned all (and more) this in barber school . . . there's lots more where this came from . . .