Almost everyone will suffer from hair thinning at some point or the other. The main reason for hair thinning is Di-Hydrotestosterone (DHT). This hormone is a byproduct of Testosterone, which is converted to DHT by the enzyme 5-alpha reductase. The DHT in the scalp binds to receptors on the hair follicle and causes major hair thinning. Intense hair thinning leads to baldness in both male and female. There are products available that can prevent thinning of hair. These products are called DHT blockers.
There are some surgical treatments that are available for preventing thinning of hair. They can be highly successful. Here, the surgeon removes a patch of hair in order to create numerous hair grafts. This helps hair to grow in bald areas. This process can be extremely fruitful but expensive.
Hair thinning treatments can have harmful side effects. So even if it is prescribed for you, you need to be careful. You must not expect to have a full head of curls though. With these treatments, you can only expect to prevent complete baldness.