In the proverbial battle of the sexes, men have the dubious distinction of winning when it comes to hair loss – doing it earlier, faster and more extensively than women. In fact, 16 to 25 percent of men begin balding between ages 18 and 29, with the incidence of hair loss increasing with age (approximately 53 percent of men aged 40 to 49 have moderate to extensive hair loss, and two-thirds of men start balding by age 60).

Why do men lose hair “better” than women? In most cases, it’s simply a matter of hormones and genetic predisposition. Let me explain:

The most common type of hair loss in men is called male pattern baldness (the medical term is androgenetic alopecia). This pattern begins at the hairline, which gradually recedes to form an “M” shape. The hair at the crown of the head also begins to thin. Eventually, the top of the hairline meets the thinned crown, leaving a “U” pattern of hair around the sides and back of the head.

Men with male pattern baldness have elevated levels of a sex hormone called dihydrotestosterone (DHT) in the scalp, which causes the hair follicles to shrink and stop growing hair. And while this type of baldness is typically hereditary, it is not inherited solely from your mother’s male relatives (contrary to a long-standing myth). The fact is that the baldness gene can come from either side of the family, or both.

So what if your DHT levels are normal and all your relatives have full heads of hair – but you’re still losing yours? Many diseases – such as diabetes and thyroid issues – have hair loss as a symptom, so it’s vital to obtain a proper medical diagnosis to ensure there’s no underlying illness causing your hair loss. When no illness is involved, and you’re not undergoing chemotherapy or radiation treatment that’s causing the hair loss, here are some of the other usual suspects I see in my practice:

Telogen effluvium is the medical term for hair loss that occurs after a shock to your system, such as major surgery, an illness or psychological trauma. Certain medications such as beta blockers, anticoagulants, antidepressants, NSAIDs and retinoids can also contribute to this condition, as can extreme weight loss from crash diets, iron deficiency or low protein intake.

While it’s completely normal to lose about 100 hairs a day as part of our hair’s natural growth cycle, people with telogen effluvium often see their hair coming out in handfuls. To understand why, it’s important to understand this growth cycle.

Human hair grows about a half-inch per month. Each hair grows for two to six years, rests at that length for a short time, then falls out. A new hair begins growing in its place soon after. At any one time, about 85 percent of the hair on your head is in the growth (anogen) phase, and 15 percent is in the resting (telogen) phase. With telogen effluvium, stress or other conditions cause hair follicles to prematurely enter the resting phase, triggering major hair loss all at once. Fortunately, this condition is usually temporary and self-correcting.

Alopecia areata is an autoimmune skin disease that causes hair loss on the scalp and other parts of the body. It usually starts with one or more small, round, smooth patches on the scalp and can progress. It affects more than 4.7 million Americans, and the disease course is different for each person.

Tinea capitis is a disease caused by a fungal infection of the scalp, eyebrows and eyelashes, where it attacks hair shafts and follicles. Hair loss is common in infected areas.

The good news is that there’s a range of effective medical and surgical treatments for most of these conditions. The most important first step is to obtain an accurate diagnosis – from a qualified physician –of the cause of your hair loss. This requires a comprehensive, in-person evaluation of your health history, diet, hair loss history, and expectations for hair restoration.