Hair growth follows a natural cycle involving growth, rest and shedding phases, and every follicle on the scalp moves through that cycle independently. Over the course of a lifetime, factors like genetics, hormonal shifts, scalp health and nutritional status can all influence how that cycle behaves. Androgenetic alopecia, the most common form of hair loss, involves follicles becoming progressively smaller under the influence of dihydrotestosterone, a process known as miniaturization.[1][2] In men, this process often begins at the hairline and crown. In women, it tends to present as diffuse thinning across the top of the scalp while the frontal hairline remains intact.[3] Hormonal events including perimenopause, menopause, pregnancy, postpartum recovery and thyroid conditions can all meaningfully affect the hair growth cycle as well.

Not all hair loss is tied to genetics or hormones. Alopecia areata is an autoimmune condition in which the immune system targets hair follicles, causing sudden patchy loss that can fluctuate over time.[4] Telogen effluvium, a diffuse shedding that typically appears two to three months after a trigger such as illness, significant weight change, high stress or certain medications, is another common pattern.[5] Scalp conditions including seborrheic dermatitis, psoriasis and chronic inflammation can also disrupt follicle function over time.[6] Because hair loss can have so many different drivers, a thorough evaluation from a healthcare provider is often more useful than relying on guesswork or generic products.