oestrogen

The drug is suitable for those with certain gene mutations that affect up to half of people with hormone receptor positive secondary breast cancer - the most common type, which grows in the presence of oestrogen.

Hormone levels change during the menopause - most significantly oestrogen, which controls the menstrual cycle and contributes to a number of other bodily processes.

Fat in the body helps make the sex hormone oestrogen.

In Scotland, 43 patients have continued to receive either puberty blockers or "gender affirming hormones" such as testosterone or oestrogen, as they were prescribed the treatments before the April decision was made.

But the evidence suggests the vast majority who start on puberty blockers go on to take cross-sex hormones - oestrogen or testosterone.