Causes of hair loss are:
Age related baldness: this may be male pattern (loss of hair starting from the center or from the temporal regions) or female pattern (thinning of hair throughout the scalp).
Disease: the three most common diseases that cause this are diabetes, thyroid disorders and Lupus.
Nutrition; poor diets not rich enough in protein or iron.
Medications: drugs used for gout, depression, blood thinners, anti-hypertensives, birth control pills, chemotherapy.
High fever or other illness: hair may thin out after about three months of a severe illness due to stress.
In your case, if you have ruled out all other causes, then it is most likely to be female pattern baldness.
The treatments that you can do is:
Iron supplements: you should take an iron suplement available OTC at pharmacies.
High proten dietMinoxidil (Rogaine) : apply twice daily to the scalp.
Finasteride (Propecia) : available on prescription for male pattern baldness.
You can look up the following sites:
http://familydoctor.org/081.xmlhttp://www.nlm.nih.gov/medlineplus/ency/article/003246.htmI hope this answer was helpful. If you need more information, feel free to ask. For accepting this answer, please click on the green 'accept' button below. Feedback/Bonus will be warmly appreciated.