Objective: To evaluate the effects of oral estradiol and transdermal 17β-estradiol on serum concentrations of IGF1 and its binding proteins in women with hypopituitarism.
Design: Prospective, comparative study.
Methods: Eleven patients with hypopituitarism were randomly allocated to receive 2 mg oral estradiol (n=6) or 50 μg/day of transdermal 17β-estradiol (n=5) for 3 months.
Results: The oral estrogen group showed a significant reduction in IGF1 levels (mean: 42.7%±41.4, P=0.046); no difference was observed in the transdermal estrogen group. There was a significant increase in IGFBP1 levels (mean: 170.2%±230.9, P=0.028) in the oral group, but not in the transdermal group. There was no significant difference within either group in terms of median IGFBP3 levels. In relation to lipid profiles, there was a significant increase in mean high-density lipoprotein cholesterol levels in the oral group after 3 months of treatment, (27.8±9.3, P=0.003). We found no differences in the anthropometric measurements, blood pressure, heart rate, glucose, insulin, C-peptide, or the homeostasis model assessment index after treatment.
Conclusions: Our preliminary data indicate that different estrogen administration routes can influence IGF1 and IGFBP1 levels. These findings in patients with hypopituitarism have an impact on their response to treatment with GH, since patients receiving oral estrogen require increased GH dosage. These results suggest that oral estrogens may reduce the beneficial effects of GH replacement on fat and protein metabolism, body composition, and quality of life.