I have read that hair diameter is thickest near the bulb and thinnest as it reaches the tip. Recently I have seen some fallen hairs with the diameter thickest at the center and thinner as it reaches the bulb and tip. Is this indicative of hair loss?
The hair shaft should be uniform in its thickness through its entire length when the hair is shed during the normal growth phase that all hairs go through. If there is active miniaturization that radically sets in, then that could explain what you see in some of the hairs that you observed. In the miniaturized hair, the hair probably grows slower than in the normal state, so a hair that you are looking at (lets say one inch long) might have taken some time to find its way out (more than the normal 1/2 inch of growth per month). The best indication of hair loss is to assess the degree of miniaturization that is present throughout the scalp, particularly the areas that are thinning. I hope that this helps.