University Hospital Maatricht Maastricht, The Netherlands
Gudmundur Johannsson and Bengt-Åke Bengtsson
Research Center for Endocrinology and Metabolism Sahlgrenska University Hospital Göteborg, Sweden
We read with great interest the report of Burman et al. (1), which showed that the reduction in body fat percentage and abdominal fat mass after 9 months of rhGH replacement therapy was significantly larger in GH-deficient men than in women. Furthermore the report suggested that the change in body fat distribution resulting from replacement therapy differed between GH-deficient men and women. The concomitant increase in fat-free mass did not differ significantly between men and women. These results support our previous findings of gender differences during GH replacement in adult hypopituitary patients (2, 3). However, one has to be aware of the distinct differences in body composition and fat distribution between males and females in both normal and hypopituitary adults. After adjusting for these baseline differences the gender-specific difference in change of body composition during GH-replacement therapy was clearly attenuated (2). Concerning the effect of GH on bone metabolism, a 2-yr GH-replacement study demonstrated that markers reflecting bone resorption and bone formation increased more in men than in women, but total body mineral density increased more in women (3), reflecting the fact that estrogen, in contrast to GH, attenuates bone remodeling. Regarding the gender differences during GH-replacement a confounding factor may be that, in all previous trials, including the one by Dr. Burman and colleagues, GH was administered according to body weight or body surface area, neglecting that healthy fertile women secrete more GH than young men (4). This may have led to relative underdosing in women and overdosing in men.
The question can be raised whether the apparent gender-specific body composition response to GH is limited to a GH status varying from deficiency towards adequate substitution. In a previous study, using multiscan computed tomography (CT), we have shown that in patients with acromegaly the subcutaneous adipose tissue volume increased 53% in males and only 20% in females, 1 yr after transspheniodal adenectomy (5). The decrease in muscle and skin volume did not significantly differ between both sexes. In contrast to the dual energy x-ray absorptiometry (DXA) method used by Burman and colleagues (1), the multiscan CT technique specifically enables the determination of the visceral adipose tissue volume, which is important with respect to insulin resistance and lipoprotein concentrations (6). In acromegaly the visceral adipose tissue volume increased 84% in males compared with 25% in females after adenectomy, and we provided evidence that the adipose tissue distribution in acromegalic men changed significantly (P < 0.005) after therapy, while this was not the case in women (5). Hence, we would like to conclude that GH has more pronounced effects on abdominal/visceral adipose tissue in men than in women, varying from GH-deficiency towards acromegaly, but that the large baseline differences in body composition between men and women should be considered in the evaluation of gender-specific responses to GH.
Footnotes
1 Received June 11, 1997. Address
correspondence to: Robert-J.M. Brummer, MD PhD, Department of Internal
Medicine, University Hospital Maastricht, P.O. Box 5800, NL-6202 AZ
Maastricht, The Netherlands.
References
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