When Does Finasteride Thicken Up Hair Shafts?

Does finasteride thicken up hair shafts DURING the growth phase, or (with good results of course) does it thicken up only when a new cycle begins?

I do not have a definite answer to your question, but I can venture a guess. As the usual hair cycle is over 2 years in most men and we see benefits from Propecia in 8-12 months, I would guess that as the hair shaft emerges from its source, the shaft thickens. Of course, as the hair growth above the skin grows at about 1/2 inch per month, I would expect that the thickening of the hair shaft starts quickly and increases over time.

All miniaturized hairs are not equal. Let’s say that the shafts that have lost 90% of their bulk will be slower to benefit (if they benefit at all) than those miniaturized hairs which have lost 20% of their bulk. The impact on new hair should be better if these new hairs are healthy ‘terminal’ hairs that have considerable life left in them. When I see patients for follow-up examinations and comparison studies, I see that there are less miniaturized hairs and more of thicker shaft hairs, and as we use the bulk analysis instrument on more patients, the answer to your questions will be much more clear.

I think you have a great question from a scientific perspective. I wish there was a time lapse photo of a hair shaft under the influence of Propecia (or even Rogaine).