[Transdermal and oral hormone substitution with estrogens: a comparison]

Application of oral estrone/estrone sulfate and estradiol leads in the circulation to a similar estradiol/estrone-ratio which is below one using oral estrogen while using transdermal estradiol the estradiol/estrone-ratio is greater than one. Overall, transdermal application leads to higher bioavailability of estradiol compared with the oral use of estrone/estrone sulfate or estradiol. Oral estrogens increase hepatic protein synthesis (i. e. SHBG) which is not the case using transdermal application. In addition, by this the bioavailability will be increased. The effect on clinical symptoms is similar and the same is true for the effect on bone. Regarding the lipid metabolism elevation of HDL and thereby improvement of the HDL/LDL-ratio by oral estrogens is obvious. However, triglycerides will be elevated. Overall, both forms of application of estrogens have a positive effect on the cardiovascular system. Different effects on IGF-1 and growth hormone raises the question of the effect on oncogenesis.