It is apparent to even the casual observer that a number of women lose hair dramatically in their post-menopausal years. This is because sexual characteristics are controlled by the balance of sex hormones. Both male and females normally have male and female hormones, males will have more male hormones and females will have more female - but they all have both types. This doesn't mean to say that the person is any less female. It simply means that some body systems are more likely to change their behaviour.
Hair is probably one of the most easily affected.
After the menopause susceptible women may lose the protective effects of the female hormones. The hair follicles in women have patterns of sensitivity to androgens just as men do. The female patterns are different to men in detail but usually involve the front of the scalp, just like males. Genetic hair loss in women can occur before menopause. The balance of hormones can vary between individuals, by chance some are nearer to a male balance and, for reasons that are unknown, can fall below the level.