This sounds more serious than just a hormonal problem. It may be fear aggression or the aggression could be caused by a medical condition.
Prior to neutering, your vet should really check for infections that may affect the brain and hormones, which may include, but are not limited to: hyperthyroid, nutritional deficiencies, toxoplasmosis, head trauma, Feline leukemia, feline aids, FIP and many many more.
If your vet has determined that the cause is purely behavioral, your cat may require behavioral modification medication.
I used to have a cat that I found once slinking around the corners of my room growling and hissing. It was normally such an affectionate and intelligent cat! There were noises outside, of trucks, but still I couldn't understand what was happening to him.
Anyway soon after this frightening incident I got my cat neutered (He was mature at this stage. About 3 years old)
IMMEDIATELY there was a change and he stopped any neurotic behavior, and was much calmer, and much more content and happy. He still had good energy and loved to run around outside, but was a happier cat.