From: Progesterone vs. synthetic progestins and the risk of breast cancer: a systematic review and meta-analysis
Study name
Type of MHT
Progesterone
Synthetic progestins
Espie et al. 2007 [16]
Oral estradiol
NR
0.81 (0.23–2.85)
Transdermal estradiol
0.46 (0.13–1.62)
1.07 (0.50–2.27)