there are many causes of hair loss, the most common cause in both men and women is androgenic alopecia. This condition is due to high levels of the hormone dihydrotestosterone (DHT) which causes the miniaturisation and eventual death of hair follicles. This condition can affect young men and women and will typically lead to progressive hair loss as a person ages. Getting diagnosed and treated as early as possible is critical to slowing down the progression of the disease.

Hair loss or alopecia is a very common but emotionally distressing condition. Up to 70% of men and 50% of women will experience hair loss at some point in their lives.

Finasteride is a type 2 5 alpha reductase inhibitor. What this means is that finasteride supresses the conversion of the hormone testosterone into dihydrotestosterone. It is available in topical (applied onto the scalp) or oral forms. The topical formulations are newer and are thought to allow the use of much smaller doses for the same effect. Topical formulations of low dose finasteride are thought to minimise the chance of sexual side effects. You must continue to take this medication to maintain the effect of treatment. In addition to slowing or preventing this hair loss, some patients actually experience a regrowth of hair with this medication.
Dutasteride inhibits both types 1 and 2 5 alpha reductase and leads to a larger suppression of circulating dihydrotestosterone (90% vs 70% from finsateride). Treatment with finasteride is more likely to result in sexual side effects than finasteride. It is typically only available in oral formulations.
Minoxidil is available as a foam or a solution that is applied to the scalp daily to prevent hair loss. It is a vasodilator which is thought to work by increasing the oxygen supply to hair follicles that have become miniaturised.
Ketoconazole is an anti-fungal medication which in some studies has shown effect for treating androgenic alopecia. It is unknown whether this benefit stems from its anti-androgenic properties or whether it acts on hair loss by other mechanisms. It is not as effective as finasteride or minoxidil but may be useful in combination with the two.
Other drugs are available for certain rarer types of hair loss, however, effectiveness is highly variable and treatment is highly dependent on correct diagnosis.