Anastrozole (Arimidex®) is a selective aromatase inhibitor (a drug that interferes with the making of oestrogens). Reduction in serum oestrogen levels in a hormone-receptor positive breast cancer patient is clearly beneficial in delaying the regrowth of breast cancer cells in the body. Anastrozole is effective in reducing serum oestrogen levels which results in several significant side-effects with 2 being of significant importance; joint pain and stiffness and bone thinning or osteoporosis. The question being asked in this trial is if replacement of testosterone to women receiving Anastrozole can have a reduction in these 2 common side-effects. Women normally have circulating in their blood 3 major sex hormones: oestrogen, testosterone and progesterone. Each of these is produced by the ovaries. Oestrogen is also made throughout the body but particularly in body fat. Testosterone can also be made in other parts of the body from hormones (DHEA and DHEAS) that are produced by the adrenal glands. At the time of natural menopause, surgical removal of the ovaries or destruction of the ovaries by chemotherapy, oestrogen and progesterone levels fall precipitously. Testosterone levels however fall more gradually with increasing age such that a woman in her forties has on average only half of the testosterone circulating in her bloodstream as does a woman in her twenties. After a woman has her ovaries removed by surgery or destroyed by chemotherapy testosterone levels can fall by up to fifty percent. However testosterone does not change across menopause, although this varies somewhat between women. Testosterone is known to have many physiological roles in women. Firstly, oestrogen is actually made from testosterone, and without the ability of our bodies to make testosterone we cannot make oestrogen. Testosterone appears to have direct independent effects in different parts of the body, and some women may experience a variety of physical symptoms when their blood levels fall. Anastrazole almost completely blocks the formation of oestrogen from testosterone. Thus the question being asked in this trial is, can increasing the blood level of testosterone reduce specific side-effects caused by reduction availability of hormones in joints and bones.