Oestrogen protects the lining of blood vessels, so post-menopausal women lose their protection against heart disease, and their risk of having a heart attack or stroke quickly catches up with the same risk for men. 

Oestrogen is also believed to be protective against Alzheimer’s disease, providing a possible explanation for why dementia affects more women than men (who convert the testosterone they produce into oestrogen inside brain cells). Nothing has been proven yet, however. One study (in rats) found oestrogen increased connections in the area of the brain called the hippocampus, responsible for learning.  

Lack of oestrogen also affects bone health: one in three women over 50 will develop fractures due to the fragile bone condition osteoporosis, where bones become porous and break more easily. “HRT has been shown to significantly reduce the risk of osteoporotic fractures and lead to a significant reduction in cardiovascular events and mortality,” said Haitham Hamoda. “There is an increased risk of breast cancer, but that is small.”