A handful of other causes account for the remaining thirty per cent, many of which are temporary. The social stigma attached to female hair loss means that people are often slow to visit their dermatologist (instead preferring to buy an over the counter remedy). It's a short-sighted move. A specialist should always be your first port of call as they are qualified to dig into your medical history to identify any other possible causes.
Hormones are known to play a key part in hair loss, so it isn't all that surprising to find that anything that alters your hormonal balance may lead to hair loss. Up to half of all women lose hair after child birth; some believe this is part of the body's mechanism for coping with the trauma of birth, other believe it's directly caused by increased levels of progesterone (which triggers the 'resting' phase of the hair cycle). Luckily this type of hair loss is temporary and typically everything's back to normal by the child's first birthday. Certain female oral contraceptives containing male hormones can also cause hair to thin.
A number of medicines have been implicated in hair loss; if you suspect this to be the case your doctor or physician may be able to prescribe an alternative drug. The list is exhaustive, but includes medicines to treat cancer, blood pressure, thyroid problems, diabetes and anemia. As with most aspects of hair loss it's worth remembering that things don't happen overnight, and that hair loss may occur up to 6-9 months after the medicine is taken. This 'time lag' also applies to hair loss brought about by stress (such as illness, surgery, accidents, etc...).
Poor diet is another frequently sighted cause of female hair loss. Protein, iron and vitamin deficiencies can be easily rectified with supplements (although high levels of vitamin A are thought to make things worse). A much more significant threat is posed by crash diets, which the body interprets as trauma. Similarly rapid weight gain may trigger hair loss.