I’m facing excess hair loss at the age of 20 accompanied by dry scalp, what could be the reason?

The first step in evaluating hair loss in women, after a detailed history and physical exam, is to rule out any underlying medical causes of hair loss which can be treated. If clinically appropriate, the following disease processes should be considered: anemia, thyroid disease, connective tissue disease, gynecological conditions and emotional stress. Furthermore, over 50% of women going through change of life hormone fluctuations (menopause) experience significant hair loss. It is also important to review the use of medications that may cause hair loss, such as (but not limited to) oral contraceptives, beta-blockers, Vitamin A, thyroid drugs, coumadin, and prednisone. The following laboratory tests have been recommended to rule out the aforementioned medical conditions:

Some common blood tests for female hair loss:

Sex Hormone tests
SHBG (Sex Hormone Binding Globulin) used to test status of male hormones
Estradiol is a sex hormone
FSH (Follicle Stimulating Hormone) *not hair follicle but follicle in the ovary*
LH (Luteinizing Hormone) is a sex hormone
Free Testosterone
Total Testosterone
ANA (Anti Nuclear Antibody) used to test for Lupus or other autoimmune diseases
TSH (Thyroid Stimulating Hormone) used to test for hyper or hypo-thyroid disease
Test Iron status
TIBC (Total Iron Binding Capacity)
Ferritin
Iron