change in taste

does your spit ever change flavors? You can feel the new flavor leak over your back molars, seeping out of your salivary glands. What causes this change in taste? When I first noticed it I thought I had chipped a tooth and that was what the inside tasted like. Now I think it might be a hormone like serotonin or melatonin or something of that sort, since I only notice it right before bed. I didn't know hormones had flavors. It's interesting. You never think of what spit tastes like. It's just always there, seemingly unchanging and so you stop noticing. But should there be a variation in the constant, suddenly you notice- and are forced to wonder, why does my spit change flavor?