Background: Transdermal (TD) estrogen is often preferred over the oral route in postmenopausal and in GH deficient women taking estrogen, but this has not been studied in detail in girls.

Objective: To study the metabolic effects of oral vs. TD estrogen in GH-treated girls with Turner syndrome.

Design/Methods: 11 girls with Turner syndrome, mean age 13.4 ± 0.5 (SE) yrs on GH for 6mo prior were recruited. Studies included: ¹³C-leucine and d5-glycerol infusions, indirect calorimetry, DEXA, hormone and substrate measurements. They received, in random order, 17 estradiol orally (0.5, 1 and 2mg, 2w each) and TD (0.025, 0.0375 and 0.05mg, 2w each) and studies repeated after each 6w course with 4w washout in between.

Results: Rates of whole body protein turnover, oxidation and synthesis, lipolysis, lipid, carbohydrate oxidation, and resting energy expenditure were unaffected by either form of estrogen, nor were lipids, insulin and fibrinogen concentrations. Plasma IGF-I concentrations did not change clinically significantly with either form of estrogen, despite higher estrogen concentrations after oral estrogen. Estradiol concentrations did not correlate with any variables measured.

Conclusions: In GH-treated girls with Turner syndrome, neither oral or TD estrogen adversely affect rates of protein turnover, lipolysis and lipid oxidation rates, nor plasma lipids, fibrinogen or fasting insulin concentrations. There was no clinically significant change in IGF-I concentrations after either form of estrogen. In aggregate, these data suggest that the route of delivery of estrogen does not adversely affect these metabolic effects of GH in young girls with Turner syndrome.