Human versus non-human sex steroid use in hormone replacement therapies part 1: Preclinical data.


Division of Geriatrics and Gerontology, Department of Medicine, University of Wisconsin-Madison School of Medicine and Public Health, USA; Geriatric Research, Education and Clinical Center, Veterans Administration Hospital, Madison, WI, 53705, USA; School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Joondalup, 6027, WA, Australia. Electronic address: [Email]


Prior to 2002, hormone replacement therapy (HRT) was considered to be an important component of postmenopausal healthcare. This was based on a plethora of basic, epidemiological and clinical studies demonstrating the health benefits of supplementation with human sex steroids. However, adverse findings from the Women's Health Initiative (WHI) studies that examined the 2 major forms of HRT in use in the US at that time - Premarin (conjugated equine estrogens; CEE) and Prempro (CEE + medroxyprogesterone acetate; MPA), cast a shadow over the use of any form of HRT. Here we review the biochemical and physiological differences between the non-human WHI study hormones - CEE and MPA, and their respective human counterparts 17β-estradiol (E2) and progesterone (P4). Preclinical data from the last 30 years demonstrate clear differences between human and non-human sex steroids on numerous molecular, physiological and functional parameters in brain, heart and reproductive tissue. In contrast to CEE supplementation, which is not always detrimental although certainly not as optimal as E2 supplementation, MPA is clearly not equivalent to P4, having detrimental effects on cognitive, cardiac and reproductive function. Moreover, unlike P4, MPA is clearly antagonistic of the positive effects of E2 and CEE on tissue function. These data indicate that minor chemical changes to human sex steroids result in physiologically distinct actions that are not optimal for tissue health and functioning.


17β-estradiol,Bioidentical hormones,Brain,Cancer,Cardiovascular disease,Cell proliferation,Cognitive health,Conjugated equine estrogens,Coronary blood flow,Coronary dilation,Endocrine,Equilin,Estrone sulfate,HRT,Heart,Hormone replacement therapy,Hypothalamic-pituitary-gonadal axis,Learning,Mammary gland,Medroxyprogesterone acetate,Memory,Menopause,Ovaries,Premarin,Prempro,Progesterone,Reproductive tissues,Thrombosis,Uterus,