Objective: Elderly patients with hypothalamic-pituitary disease exhibit a reduction in GH secretion distinct from the decline in GH secretion related to age. GH deficiency in young adults causes a change in body composition, with increased fat mass (FM) and reduced fat free mass (FFM), similar to that seen as a result of the normal ageing process. The aim of this study was to determine whether organic GH deficiency in elderly patients may cause changes in body composition beyond those due to ageing.
Subjects: Twenty-one patients (15 male) with documented pituitary disease and 24 controls (17 male) matched for age, height, weight and BMI, all over the age of 60, in whom GH status had been defined by a 24-hour GH profile and an arginine stimulation test.
Measurements: Serum was taken for fasting IGF-l and IGFBP-1 estimations. Total and regional FM and FFM were determined using dual-energy X-ray absorptiometry.
Results: FM (median (range)) was increased in the patients, 27.76 (19.25-50.24) vs 21.23 (8.81-49.15) kg in the controls (P < 0.005). FM was significantly increased in the arms, legs and trunk in the patients compared with the controls. The proportion of fat deposited centrally did not differ significantly between the two groups (57.0% (47.6-65.1) in the patients vs 55.3% (44.1-63.8) in the controls, P = 0.25). There was an inverse relation between total FM and serum IGFBP-1 present in the patients, p = -0.632, P < 0.005, and in the controls p = -0.467, P < 0.05, but the relation between total FM and area under the GH profile was significant only in the controls (p = -0.651, P < 0.001) and not in the patients. FFM (51.19 (26.96-69.18) kg in the patients vs 51.55 (32.35-60.53) kg in the controls, P = 0.99) and serum IGFBP-1 levels did not differ significantly between the two groups.
Conclusion: Organic growth hormone deficiency causes changes in body composition beyond the changes associated with the ageing process. These changes differ from those seen in younger GH deficient adults in that they are limited to an increase in FM with no change in FFM. These findings indicate that even in the elderly, in whom GH secretion is normally very low, the additional imposition of GH deficiency due to organic disease has significant biological impact.