ORAL AND TRANSDERMAL OESTROGEN TREAT- MENTS HAVE DIFFERING EFFECTS ON GROWTH HORMONE(GH) SENSITIVITY IN HYPOPITUITARY WOMEN RECEIVING GH REPLACEMENT

Background: The route of oestrogen replacement has an influence on GH sensitivity in hypopituitary women but the practical relevance of this effect remains unclear. Objectives: To compare the effects of oral and transdermal oestrogen replacement on GH requirement in adult females with hypopituitarism receiving GH replacement. Methods: This cross-sectional, observational study included 69 GH-deficient women each receiving a stable dose of GH replacement therapy. Three groups of patients were investigated: a control population without oestrogen replacement (n = 38), and hypopituitary women receiving oral (n = 18) or transdermal (n = 13) oestrogen substitution.  A single pre-prandial blood sample was taken between the hours of 08:30-09:30 from each patient for the measurement of serum IGF-I, serum total cholesterol, serum total triglycerides, serum HDL-cholesterol and serum LDL-cholesterol.  The relevant demographic, anthropometric and clinical (e.g. exogenous GH requirement) data were also recorded. Results: The mean daily GH requirement was 90% higher in the women receiving oral oestrogen compared with the control population (p<0.001), and 53% higher in those receiving transdermal oestrogen compared with the control women (p<0.01).  The mean daily weight-corrected GH dose required to achieve target IGF-I levels was higher for oral vs. transdermal subjects (12.0±3.7 µg/kg∙day vs. 8.3±3.0 µg/kg∙day, respectively, p<0.01).  Despite this higher GH dose the mean IGF-I levels were lower in oral vs. transdermal patients (24.2±12.6 nmol/L vs. 35.0±16.1 nmol/L, respectively, p<0.05). Conclusion: This study shows that oestrogen replacement per se reduces sensitivity to exogenous GH in hypopituitary women.  The route of oestrogen replacement is an important influence on GH requirement and those on oral oestrogen are clearly more GH resistant than women using transdermal preparations.  The route of oestrogen administration is of practical and economic importance in the management of the hypopituitary woman receiving GH replacement. Keywords: GH replacement; GH sensitivity; hypopituitarism; oral oestrogen; transdermal oestrogen.