What Causes Baldness

• Male pattern baldness is the gradual loss of hair on certain parts of the scalp, often starting with receding hair at the temples or on top of the head. The cause is usually genetic and results when the male hormone, testosterone, is converted into dihydrotestosterone (DHT), which slows or stops hair growth.
  
  

How Propecia Works

• Finasteride -- the chemical name for Propecia -- blocks the formation of DHT in the scalp. Merck developed Propecia to treat mild to moderate male pattern hair loss on the top and middle front of the head.
  
  

Dangers to Women

• According to the National Center for Biotechnology Information, finasteride can harm a male fetus if taken by a pregnant woman or absorbed through the skin. It warns that women who are, may be or could become pregnant should not take finasteride or touch broken or crushed finasteride tablets. Talk to your doctor if you are pregnant and take or touch finasteride tablets.