The average hair loss rate is about 100 strands a day, but natural hair loss tends to go unnoticed because the cycle of new growth evens it all out. It’s when the hair growth cycle gets interrupted and hair follicles become destroyed or dormant after shedding their last hair that noticeable thinning occurs. While family history (genetics), medical conditions, prescriptions, supplements, stress, and hair care can all play a role in a thinning hairline, most hair loss cases, including those of androgenic alopecia, can be traced back to hormones, specifically dihydrotestosterone (DHT).
For the most part, because women have a very small fraction of the amount of testosterone often found in men, women can still experience DHT-triggered hair loss, but it more often appears as thinning rather than a receding hairline that is more typical in males. As well, in women, oestrogen plays a protective role against DHT, encouraging hair to stay in its growth phase, but when oestrogen levels drop during menopause or post-pregnancy, DHT increases and hair loss and thinning result.
Of course, hormone production levels, like hair growth, also follow cycles, which is the main reason men and women experience aging at different rates. For women, hormones shift and change throughout different stages of our lives, including during puberty, pregnancy, childbirth, menopause, and even with our monthly cycles. For men, testosterone levels tend to decline more gradually, with an average drop of 10% each decade starting in their 30s. Depending on how these hormonal cycles correlate with one’s hair growth cycle, hair loss and thinning may appear to dramatically develop short-term but show signs of slowing down long-term.