Excess testosterone can also cause excess sebum production and despite what you read, excess sebum can kill hair follicles. I bought some Nioxin shampoo from Amazon which works good although I wish I had used it sooner to save my hair I lost.
Although yours is itchy maybe it's Psoriasis but there are also Psoriasis shampoos and also dandruff shampoos. My teenager was losing hair and her doctor prescibed a dandruff shampoo. You may have to try a few things. The Nioxin is expensive.