Hair loss in most cases is largely genetic and induced by hormones. You can be perfectly healthy and experience significant hair thinning. Medical conditions can certainly exacerbate it.
Possible conditions that contribute to hair loss are (but in no way limited to):
Various forms of Alopecia: Including Androgenic Alopecia, Scarring Alopecia, Alopecia Areata, Alopecia Universalis and Traction Alopecia.
Thyroid Disorder: Hair problems can be the first sign of an underlying illness, particularly for those suffering from Thyroid Undersecretion. Full recovery of the hair is achievable for those suffering, providing the condition is diagnosed and treated in its early stages.
Iron Deficiency: Lack of iron in the diet is a common cause of hair loss in women. Those who are vegetarian or have suffered from an eating disorder are particularly prone to this type of hair loss, though it can affect anyone.
Trauma Hair Loss: The frequent use of hair styling products and devices, as well as tight hairstyles, can lead to hair loss taking place in certain areas. If the condition is treated prior to the scalp being damaged, hair will normally regrow. Afro-Caribbean hair can be particularly suspectable to this kind of hair damage. Click here for more information.