Hair thinning in males can be caused by a variety of factors, including genetics, hormonal changes, medical conditions, and aging. The most common cause of hair loss in men is male-pattern baldness, which is related to genes and male sex hormones. Male-pattern baldness usually follows a pattern of receding hairline and hair thinning on the crown. Other causes of hair loss in men include certain medications, too much vitamin A, not enough protein, illness, stress, and autoimmune diseases like alopecia areata. Treatment options for male-pattern baldness include FDA-approved medications like topical minoxidil and oral finasteride. Its important to note that catching hair loss early and starting treatment soon after noticing it can lead to better results.