Route of Estrogen Administration Helps to Determine Growth Hormone (GH) Replacement Dose in GH-Deficient Adults1

We prospectively studied two groups of GH-deficient patients during GH therapy based upon exposure of the liver to elevated (oral estrogen) or not elevated (endogenous or transdermal) sources of estrogen. We wondered whether higher concentrations of estrogen at the liver level (oral estrogen) might inhibit insulin-like growth factor I (IGF-I) secretion and alter exogenous GH requirements. In this study we compared GH replacement requirements in these two groups of women as well as with GH-treated adult hypopituitary males. The final GH dose was based upon maintenance IGF-I levels in the mid- to high normal range adjusted for age and sex or symptom tolerance. Each group [women taking oral estrogen (n = 12), women not taking oral estrogen (n = 13), and men (n = 12)] was similar in age and final IGF-I concentration. Women taking oral estrogen required 10.6 +/- 0.7 microg/kg x day or 867 +/- 45 microg/day GH, women not taking oral estrogen required 5.0 +/- 0.7 microg/kg x day or 424 +/- 57 microg/day, and men required 4.1 +/- 0.6 microg/kg x day or 376 +/- 49 microg/day to achieve similar IGF-I concentrations. GH requirements in men were not different from those in women not taking oral estrogen, but the GH requirements in both groups were significantly different from GH requirements in women taking oral estrogen. These observations may be useful in anticipating appropriate starting and final doses of GH in adult hypopituitary patients.