1.   Once oestrogen levels fall, the bone becomes less dense and strong and more liable to fracture.

2.   The NRA believes that the small numbers of migratory fish which have returned to the Tees in recent years will continue to increase as pollution levels fall.

3.   The degree of damage depends on just how low the levels fall.

4.   The team reasoned that tired animals produce oleamide in large amounts to induce normal sleep, and that levels fall when sleep is no longer needed.