In 1991, The National Institute of Health (NIH) launched the Women's Health Initiative (WHI), the largest clinical trial ever undertaken in the United States. The WHI was designed to provide answers concerning possible benefits and risks associated with use of HRT. This study was canceled in July 2002, after it was proven that synthetic hormones increase the risks of ovarian and breast cancer as well as heart disease, blood clots, and strokes. The findings were published in The Journal of the American Medical Association (JAMA), and to this date have not been disputed.
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GnRH analogues are modified versions of a naturally occurring hormone known as gonadotropin releasing hormone (GnRH), which helps to control the menstrual cycle. When used continuously for periods of longer than 2 weeks, these drugs stop the production of oestrogen, essentially placing the body in a temporary menopausal state. This ‘starves’ the endometriosis of oestrogen, causing the deposits to become inactive and reduce. It is often recommended that a woman takes ‘add-back’ therapy or HRT to reduce or even prevent the side effects of these drugs.