STUDY ON THE GROWTH HORMONE SECRETION FROM THE PITUITARY GLAND OF PATIENTS WITH DIABETES MELLITUS

Abstract

Although it has been considered for a long time that the secretion of growth hormone from the pituitary gland may have a some causative role of pathogenesis of diabetes mellitus, the insulin-induced hypoglycemia and arginine infusion can not be employed to ascess whether or not there might be a deficiency of the pituitary gland to secrete the growth hormone in the diabetic, because the diabetes mellitus has been recognized by many clinicians as one of typical metabolic diseases. However, recently it was found that dopamine was the drug to stimulate only the growth hormone secretion from the pituitary without any changes of blood sugar levels, serum fatty acids and amino acids metabolism.
In the present study, in order to clarify how the growth hormone was secreted by several stresses from the pituitary in the diabetic, tolbutamide, arginine and L-dopa methods were compared both in normal subjects and in diabetics without obesity. In normal subjects, the pituitary secretion of growth hormone was clearly stimulated by all of three methods. However, the tolbutamide and the arginine methods were not reasonable to ascertain the ability of pituitary gland to secrete the growth hormone in the diabetic as well known. On the other hand, L-dopa, which is well known to be a precursor of the dopamine, stimulated the secretion of growth hormone from the pituitary with no influence on blood sugar and IRI in both normal subjects and diabetics. The serum concentrations of growth hormone of normal subjects and diabetics at the fasting time before the infusion of 200 ml of physiological saline containing 200 mg L-dopa for 30 min were between 2 and 4 ng/ml. Maximum concentration of serum growth hormone, approximately 30 ng/ml, were observed at 60 min after the beginning of starting of 30 min infusion of L-dopa in the normal subject. In contrast, this value of diabetics was only nearly 6ng/ml which was also observed at 60 min after the L-dopa infusion was started. The fact indicated strongly that the ability of pituitary gland to secrete the growth hormone was clearly impaired in the diabetes mellitus when it was compared with that of normal subject.