Reduced skeletal muscle mass, the most prominent component of LBM, is an important feature of adult GH-deficiency. Consistently studies have demonstrated reduction in LBM of 7-8% corresponding to approx 4 kg of lean tissue (10-14). This reduction is mirrored by an increase in fat mass, in the region of 7% (10) in GH-deficient patients compared with predicted values based on age, sex, and height. This figure has been confirmed by other investigators (13,15-19), using a variety of measurement techniques. The distribution of this excess fat mass has been the focus of a number of studies (10,13,20,16) and these have demonstrated the excess fat accumulates in a central (abdominal) distribution, mostly in the visceral component.
Both the radioisotope dilution technique and the bioimpedance (BIA) method indicate that total body water (TBW) is reduced in adult GH-deficiency (14,17). This is mainly due to a reduction in extra-cellular water (ECW, 14,19,21). Recent studies suggest that reduced plasma volume (PV, 17) and total blood volume (TBV) contribute to the reduced ECW (18).
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