What causes hair loss?

Male- and female-pattern hair loss (genetic)

By far the most common cause. Androgenetic alopecia is driven by genetics and the hormone DHT, which slowly shrinks follicles. In men it shows up as a receding hairline and crown thinning; in women, as diffuse thinning along the part. It's progressive, so earlier treatment protects more hair. See the proven treatments.

Telogen effluvium (stress shedding)

A temporary, heavy shed that hits a few months after a shock to the system — major stress, illness, surgery, childbirth, or rapid weight loss. It usually recovers on its own once the trigger passes.

Thyroid and hormonal changes

An under- or over-active thyroid, pregnancy, menopause, or coming off birth control can all cause shedding. These are worth a blood test, because treating the underlying issue often restores the hair.

Nutritional deficiencies

Low iron (ferritin), vitamin D, zinc, or protein can thin hair — crash diets are a common culprit. Correcting the deficiency usually helps.

Medications

Blood thinners, some antidepressants, beta-blockers, retinoids, and chemotherapy can all trigger hair loss. Never stop a prescribed medication without talking to your doctor first.

Alopecia areata (autoimmune)

Here the immune system attacks the follicles, causing round, patchy bald spots. It's distinct from pattern loss and needs a dermatologist's diagnosis and treatment.

Traction alopecia

Caused by tight hairstyles — buns, braids, extensions, ponytails — pulling on follicles over time. Caught early it's reversible; long-term tension can scar and permanently damage follicles.

Scalp conditions

Fungal infections (ringworm), severe seborrheic dermatitis, or psoriasis can cause shedding or breakage. Treating the scalp condition resolves the loss.

Aging

Separate from pattern baldness, hair naturally thins and grows more slowly with age as follicles become less active.

Which cause is it?

Genetic (pattern) loss is gradual and follows a predictable shape; sudden or patchy loss usually points to something else. If you're unsure — or the shedding is rapid, patchy, or paired with other symptoms — see a Fresno clinic or dermatologist to pin down the cause before starting treatment. For genetic thinning, the proven treatments and a transplant are the main paths.