Metabolic Clearance and Production Rates of Human Growth Hormone in Subjects with Normal and Abnormal Growth

The metabolic clearance rate (MCR) and production rate (PR) of human growth hormone (HGH) was estimated bymeans of a continuous infusion of 131I-HGH. Forty-four subjects, ages 4½–60 yr, with normal and abnormal growth, participated in this investigation. A significant correlation (p <.01) was found between MCR and surface area. The MCR/m2 was similar in childhood, adolescence and adult life. The MCR/m2 in ml/min (mean ±se) in 9 normal males (112 ±5) was similar to that in 8 normal females (111 ±10). The results found in hypopituitary (109 ±8) and acromegalic (118 ±16) individuals indicate that the MCR/m2 is independent of plasma HGH concentration. The MCR of HGH was normal in patients with delayed adolescence, hyperthyroidism and gonadal dysgenesis. Reduced MCR was seen in severe hypothyroidism and in one form of primordial dwarfism. The production rate (PR) of HGH in normal patients, calculated on the basis of mean plasma hormone levels, is significantly higher than that observed in hypopituitary subjects. The results of these studies indicate that, in the absence of hypothyroidism, where a low MCR/m2 may exist, the PR/m2 is a linear function of plasma HGH concentration.