Impaired prolactin response to arginine infusion and insulin hypoglycaemia in chronic renal failure

The elevated level of circulating prolactin present in the majority of uraemic patients on chronic haemodialysis is primarily due to hypothalamic pituitary dysfunction. So far this defect has been illustrated by demonstration of a blunted prolactin response to TRH and failure of l-dopa to suppress prolactin levels. In the present study two powerful prolactin and growth hormone stimuli, namely iv arginine infusion and insulin hypoglycaemia were applied in a group of uraemic patients on chronic haemodialysis and in age matched control subjects. The prolactin increments to arginine infusion (4.4 ± 1.2 ng/ml vs 17.6 ± 4.6 ng/ml, mean ± se) and to insulin hypoglycaemia (7.9 ± 1.7 ng/ml vs 31.5 ± 5.4 ng/ml) were significantly suppressed in the uraemic patients compared to the controls (P < 0.05). In contradistinction the growth hormone rise provoked by the tests were similar in the two groups. Our results provide further insight into the hypothalamic pituitary derangement in uraemic patients and confirm the presumption of an insensitivity of the lactotrophs to stimulation in uraemic patients.