Hair Loss in Men
Androgenetic alopecia (male pattern hair loss) is the most common cause of hair loss in men, affecting about 30% by age 30, 50% by 50, and 80% by 70, per a recent therapy update.
Symptoms
Gradual frontotemporal recession and vertex (crown) thinning, following the Hamilton-Norwood pattern, while the sides and back of the scalp are typically spared.
Causes and risk
Genetics and the hormone DHT (a byproduct of testosterone) acting on genetically susceptible follicles are the driving mechanism; family history is the strongest predictor.
How it is evaluated
Diagnosis is usually clinical based on the pattern. Labs (TSH, CBC, iron/ferritin, vitamin D) are checked selectively, not routinely, when the pattern is atypical or there's reason to suspect another cause.
Treatment
Both topical minoxidil and oral finasteride (1 mg daily) carry AAFP Grade A evidence, and combination therapy outperforms either alone. A network meta-analysis found finasteride generally most effective for hair-count improvement as a single agent. Finasteride carries updated FDA labeling on persistent sexual side effects in a small subset of users, which is worth discussing before starting.
When to seek care
Hair loss itself is not an emergency. Sudden patchy loss, scalp scaling with hair breakage, or hair loss with pain or scarring suggest a different cause (alopecia areata, fungal infection, scarring alopecia) and deserve evaluation rather than assuming it's the common pattern.