Metabolic clearance and plasma half disappearance time of exogenous gonadotropin releasing hormone in normal subjects and in patients with liver disease and chronic renal failure.

The metabolic clearance rate (MCR) and half disappearance time (t 1/2) of gonadotropin releasing hormone (GnRH) has been measured during and after cessation of constant infusion of exogenous GnRH. Studies were performed on normal subjects and patients with severe renal and liver disease. GnRH was quantified by a sensitive and specific radioimmunoassay which does not measure GnRH fragments. The MCR of GnRH in normal subjects was 1640+/-59.7 ml/min (23.7+/-1.8 ml/min/kg), similar to values found in 4 patients with liver disease. However in chronic renal failure an MCR of only 631+/-62 ml/min (9.1+/-0.7 ml/min/kg) was obtained. The t1/2 of GnRH after infusion was linear for 8-10 min, after which a much slower component was observed. The t1/2 of the first component ranged from 5.5 to 8 min in normal subjects, 6.5-8 min in patients with liver disease but prolonged (12-16.5 min) in patients with renal failure. It would appear that GnRH is cleared rapidly in normal subjects, that moderate liver dysfunction does not alter this, but that impaired renal function significantly prolongs the t1/2 and lowers the MCR. The kidney might be an important catabolic organ for infused GnRH; alternatively, uremia might impair catabolism non-specifically.