Many of the symptoms of PMS and perimenopausal women include water retention, headaches, irritability, weight gain, breast swelling, fibrocystic breasts, and others that are consistent with symptoms of estrogen dominance. It is now quite clear that the only bone effect of estrogen is retardation of bone resorption, and not new bone formation. There is no study that shows estrogen alone will rebuild lost bone mass. It is now clear that estrogen promotes increased replication rates of breast duct epothelial cells and progesterone decreases replication rates. Thus it would seem obvious that estrogen promotes growth of breast cancer whereas progesterone protects against it.
Hormones work on the basis of their specific molecular structure.
Any change in that structure will alter their effects. Saliva hormone assays, however, measure only biologically active steroids and thus are more accurate and more relevant.