Why do people go bald?

[guthrie]

Dragon: Just by posting the anagen cycle does not in any way support your hypothesis that hair loss is due to a shorter anagen cycle. The best hypthosesis that I have heard seems to be a decrease in testosterone levels with age. This is very logical and makes sense. Can anyone else back this up? On a related note - regarding fur shedding in dogs - the convential theory says that it is due to melatonin secretion from the pineal gland, but if it is only regulated seasonally (temperature and light), then what causes the cycle for dogs to shed their hair in near equatorial regions where the variation in sunlight and temperature would remain about constant and thus so would melatonin levels. Could testosterone also partially account for canine fur shedding?

I think that canine hair shedding will also be due simply to the fact that their hairs will grow to a certain length and then drop out, same as ours do. Otherwise dogs would be huge fluffy balls of fur.

 

[valich]

No this is not the case. Most, if not all?, breeds that originated near the equator or in hot temperature regions with maximum sunlight do not shed at all; for example, the Mexican Hairless, Egyptian Pharaoh Dog, and Barenji (moderate shedding in some areas when brought up North - originated in Central Africa). Conventional theory has it that it is tied to melatonin because you will never see a Northern breed dog shed its coat in the winter near Arctic areas, less it perish from the cold without a coat. This has nothing to do with the length of time it takes to regrow the fur. It is a seasonal cycle. the problem is that if it is tied to melatonin, which will vary with temp and light, then why doesn't the cycle change when you take a Northern breed dog and place it in the Southern Hemisphere where the winters occur when our summers occur. They still shed during our summer season even though it is winter down under. This doesn't make sense.