1. About a quarter of men will begin losing hair in their 20s, and the vast majority of cases are androgenic. Don’t be afraid to make the diagnosis of male pattern baldness even if there’s no family history, so long as hair loss fits the classic pattern of bi-temporal recession with thinning on top. Even in women, androgenic alopecia is the leading cause of hair loss.

2. Signs of non-androgenic hair loss include: itching or irritation, scaling, pain, very rapid loss, losing hair in patches, or hair loss upon starting a new drug. Useful tests are fasting glucose, ANA for lupus, and thyroid function — not hormone levels.

3. Balding is a normal part of aging, even in chimpanzees and gorillas, and no treatment is completely effective. The patient who learns to accept hair loss is usually the happiest.

4. Patients wanting treatment should understand it’s a long-term process. It takes at least three months before treatment can even be assessed, and regrowth can take years. Any new hair growth stimulated by either minoxidil or finasteride will fall out if treatment is stopped.

5. Minoxidil will cause real regrowth in fewer than a third of patients. Hair loss will be reduced or stopped in another third. A third will see no effect. Women can use minoxidil and will frequently benefit from 2%, while men do better on 5%.

6. Finasteride is only for men. Regrowth occurs in about two-thirds of cases, and hair loss is stopped in about four-fifths. Side effects are rare but can include loss of libido and gynecomastia.

7. Among non-approved treatments, topical caffeine products have the best evidence for efficacy. These include Alpecin for men and Plantur 39 for women.

8. Diet is a factor — witness the explosion of baldness in postwar Japan as people adopted a high-calorie diet. Aerobic exercise — not weightlifting — reduces levels of dihydrotestosterone, the androgen most linked to alopecia. No studies have shown, however, that diet or exercise can reduce hair loss.

9. High insulin levels are associated with vertex (crown) balding, and are probably the mechanism of an observed link between metabolic syndrome and balding.

10. Surgical techniques have improved considerably, but remain fiendishly expensive. Consider waiting a few years, as there’s plenty in the research pipeline. The nascent technique of hair multiplication, also known as hair cloning, uses stem cells to grow follicular cells in vitro and re-implant them. It should be on the market within three or four years.