Diffusion of growth hormone into thoracic duct lymph in man

Abstract

The diffusion of immunoreactive human growth hormone (IRHGH) into thoracic duct lymph following elevation of levels in serum was investigated in man. Comparisons were made with 3 other substances of known molecular weight: inulin, insulin, and Evans Blue-labeled serum albumin. Six anephric males with indwelling thoracic duct cannulas, maintained by hemodialysis in optimal metabolic condition prior to renal transplantation, were studied. Serum levels of endogenous IRHGH were increased by insulin-induced hypoglycemia and of exogenous IRHGH by the intravenous injection of Raben human growth hormone. IRHGH reached maximum concentrations in lymph 25-30 min following serum peaks of either endogenous or exogenous hormone. The diffusion pattern relative to other substances indicated that the diffusibility of IRHGH is determined by its molecular weight and suggested that IRHGH is present in serum in vivo as a monomer and unbound to other blood components. Disappearance rates of injected HGH were prolonged in these anephric individuals, supporting the importance of the kidney in the metabolism of growth hormone. © 1970 by The Endocrine Society.