It is a thinning hair treatment that is taken internally. The American Academy of Dermatology's clinical guidelines for male pattern baldness and the guidelines of the International College of Hair Surgery strongly recommend it along with minoxidil, and the U.S. Food and Drug Administration (FDA) is the only drug that can be taken internally to improve thinning hair. It was originally used as a treatment for benign prostatic hyperplasia, and was used as a hair growth agent because of the side effect of thickening hair. It inhibits the conversion of the male hormone testosterone to dihydrotestosterone (DHT), which is the cause of male pattern baldness, and as a result, the symptoms of thinning hair are improved. If you take 1 milligram every day, you will see a hair growth effect after six months to a year. It is said to be effective for 6~7% of people. In clinical trials in the United States, half of patients with mild and moderate male pattern baldness in the top and front of the head showed an effect after 3~5 months of taking the drug. And after taking it for 2 years, 83 percent of people stopped thinning hair, and 67 percent of them reported that their hair became thicker. It is true that there will be a slight increase in thick hair, but not all hair will return to normal thickness. The medicinal effect of finasteride is such that in Asians, the diameter of the hair is about 10 percent thicker on average. The average thickness of hair in Japan is 80~85 micrometers (1 micrometer is 0.001 mm), and thinning hair is thinner than 30 micrometers, so even if the hair becomes 10% thicker on average, it will not return to its original thickness. In addition, the effect varies depending on the age and the area of thinning hair. It is said that the effect is more likely to appear in young people in their 20s ~ 40s than in older people, and it is said that it works better in those who have just started thinning hair. In particular, it is said that it is not very effective in the case of thinning hair that has progressed to downy hair. It works relatively well on the top of the head, but it does not seem to have much effect on the hairline and receding on both sides of the forehead. Because it is a drug that suppresses male hormones, side effects such as decreased libido, impotence, stomach discomfort, abdominal pain, and liver dysfunction have been reported. However, the frequency of side effects is low, and even if side effects occur, they will return to normal if you stop taking them. However, due to the nature of the drug, which acts directly on male hormones, its use in women and children is prohibited. It is strictly prohibited for pregnant women and women who may become pregnant, especially if it is taken by pregnant women and if the fetus is a boy, there is a risk of malformations of the genitals. In addition, it is important to note that the PSA measurement result, which is a blood marker for prostate cancer, will be low. As with minoxidil, the effects disappear within a few months to six months when you stop taking it. If you want to stop the progression of thinning hair through the effects of the drug and maintain the current situation, you need to continue taking it for the rest of your life. However, it cannot be purchased without a doctor's diagnosis and prescription, so it is not easy to get it at