Assessment of glomerular filtration rate in diabetic nephropathy using the plasma clearance of 51Cr-EDTA

We determined the circulating dopamine levels in 17 patients with insulin-dependent diabetes mellitus (IDDM), of whom eight had amenorrhoea (DM-AM) and nine were normally menstruating (DM). Seven non-diabetic women with normoprolactinaemic, normogonadotrophic secondary amenorrhoea (AM) and nine normally menstruating women (controls) were studied. In all subjects basal blood concentrations of free dopamine (f-DA), conjugated dopamine (c-DA), epinephrine (E), norepinephrine (NE), prolactin (PRL), luteinizing hormone (LH), thyroid-stimulating hormone (TSH) and oestradiol-17β were determined and all subjects, except for three AM patients, had a Metoclopramide test performed for measurements of f-DA, c-DA, PRL, LH and TSH. Plasma c-DA was significantly (p<0.05) increased in patients with amenorrhoea compared to the respective control groups. In diabetic patients c-DA levels were significantly (p<0.05) lower compared to controls. The ratio between basal f-DA and c-DA concentrations was significantly (p<0.01) higher in diabetic patients compared with non-diabetic patients. After Metoclopramide stimulation DM-AM patients showed a significant (p<0.05) rise in c-DA, whereas this was not seen in other groups. DM-AM patients had significantly (p<0.05) lower basal PRL and LH levels than DM patients and controls. In addition DM-AM patients had a significantly (p<0.05) lower PRL response to Metoclopramide compared with DM patients. There were no significant correlations between catecholamines and basal as well as Metoclopramide stimulated pituitary hormones. This study suggests that. the abnormal pituitary hormone secretion in patients with amenorrhoea may in part be caused by an increased dopaminergic activity. In addition, we have found that diabetic patients may have abnormalities in the metabolism of dopamine.