Effect of growth hormone and insulin-like growth factor I on urinary albumin excretion: studies in acromegaly and growth hormone deficiency

Abstract

Glomerular hyperfiltration is a characteristic feature of acromegaly but it is uncertain whether albuminuria is elevated in this disease. To investigate the role of abnormal growth hormone (GH) and insulin-like growth factor I (IGF-I) levels on urinary protein excretion, we measured the overnight urinary albumin excretion rate (UalbV) and creatinine clearance in 14 acromegalic patients with metabolically active disease (fasting GH > 5 μg/l and IGF-I > 2.2 kU/l), 8 GH-deficient patients and 20 control subjects. The UalbV was higher in the acromegalic patients (median 8.4 (range 4.2–68.2) μg/min) than in the GH-deficient patients (2.0(0.9–5.9) μg/min, p< 0.001) and control subjects (3.3 (1.0– 7.8) μg/min, p <0.01). Five acromegalic patients had UalbV levels above the normal upper normal limit of 10 μg/min. Only one patient with concomitant untreated hypertension had persistent microalbuminuria. Creatinine clearance also was higher in the acromegalic patients (p<0.05) and lower in the GH-deficient patients (p <0.05) than in the control subjects. In 11 of these acromegalic cases, the lowering of GH by 63% and of IGF-I by 48%, following treatment with the somatostatin analogue (N = 10) or spontaneous pituitary infarction (N=1), reduced the UalbV by 29% to 4.9 (3.1–45.2) μg/min (p<0.01). Among the acromegalic patients (25 observations), the UalbV was related to GH (r=0.61, p<0.01), IGF-I (r=0.57, p<0.01) and creatinine clearance (r=0.54, p<0.01). In conclusion, circulatory GH and IGF-I levels influence albuminuria. Because persistent microalbuminuria is uncommon in acromegaly, it is unlikely that GH elevation alone predisposes to clinically important glomerular damage.