BLOOD AND URINE CLEARANCE OF LUTEINIZING HORMONE RELEASING HORMONE IN MAN MEASURED BY RADIOIMMUNOASSAY

Abstract

SUMMARY The clearance of synthetic luteinizing hormone releasing hormone (LH-RH) after intravenous injection has been investigated in man. Thirteen tests were performed in ten subjects, four of whom were normal, the other six had proven disease of the hypothalamo-pituitary region. The rate of disappearance of LH-RH from the circulation could be represented as a double exponential with half-times of the two components of 5·3 and 27·4 min respectively. The initial volume of distribution was 11·1 ± 1·6 (s.d.) 1 and the metabolic clearance rate 1480 ± 170 (s.d.) 1/day. There was no difference in any of these parameters between normal and abnormal subjects. Between 0·75 and 2·8% of the injected dose was excreted in the urine within 8 h, of which 48% was excreted in the first hour. The daily production rates of LH-RH were calculated from the urinary excretion rates; these gave higher results than production rates calculated from the blood metabolic clearance rate. Possible reasons for this are discussed.