Effect of intravenous and oral administration of L-dopa on HGH and TSH release.

Abstract

Effect of L-dopa on the release of human growth hormone (HGH) and thyroid stimulating hormone (TSH) was investigated with 7 normal subjects and 30 patients of endocrine disorders. The single oral dose of L-dopa 1gm and the iv administration of L-dopa 100mg showed the elevation of HGH in plasma, however no release of TSH in plasma. The possibility of increasing HGH by L-dopa administration to normal subiects was more highly observed in the iv infusion of L-dopa 100mg than in the oral dose of L-dopa 1gm. The timing of HGH response was quite variable in the oral dose of L-dopa, however was predictable (between 30 and 60min) after the iv administration of L-dopa. There were some observations where the subjects, who normally responded to arginine or insulin administration, did not respond to the oral administration of L-dopa but did respond to the iv administration of L-dopa 100mg. HGH could be increased significantly in normal subjects by L-dopa iv administration under the high glucose level in blood. The patients of hyperthyroidism, hypothyroidism and primodial dwarfism responded to Ldopa in HGH release like normal subjects. These observations suggested that L-dopa administration iv might be used as a diagnostic test of HGH release, however additional clinical experience will be needed to assess its possible usefullness.