I dont think that makes any difference at all. but yer if you're male, perfectly natural. If you're famel. No shampoo can thicken your hair, it can give it that appearance but only a miracle can make your hair grow or surgery.
I think you should see a hairdresser first. Sounds like alopecia but let the hairdresser advise you then go to the doctors. If you go to Boots in the men's section of toiletries they have bottles of Pure Silvikrin (its made from a seaweed extract) it stimulates and promotes hair growth and was used by my Mother when a hairdresser burnt her hair perming it and caused a large bald patch. Her hair recovered quickly using this and it smells nice too. That treatment would help and encourage quick hair regrowth but you really have to find out what is causing the thinning in the first place.
I have been told that taking kelp ( seaweed ) can help but it is best to ask your GP before taking vitamins or minerals especially if you take any kind of medication good luck love megan