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Hyperprolactinemia in Chronic Renal Failure

Hyperprolactinemia has been reported in 30 to 70% of patients with chronic renal failure, with more frequent elevations and higher levels being reported in women. Only a fraction of all cases, less than 5% in our series, may be attributed to drugs. What then, is the cause and significance of this yet another endocrine abnormality in uremia? Impaired degradation of the hormone accounts at least in part for this abnormality, because the metabolic clearance of human 1311-prolactin is reduced by 33% as compared with normal controls. Increased secretion and resistance to dopaminergic suppression are much more important (1, 2). The possibility that hyperprolactinemia is caused by the accumulation of a large prohormone or degraded hormone fragments has been ruled out by chromatographic studies. Sephadex G-75 gel filtration has shown that nearly all the endogenous plasma prolactin immunoreactivity in patients with renal failure is eluted as· prolactin monomer. Furthermore, 30 minutes following a single intravenous injection of 1311-human prolactin, 94% of the immunoprecipitable radioactivity is also eluted in the position of the prolactin monomer (1). Unlike other pituitary peptide hormones, the secretion of prolactin is under tonic inhibition of a hypothalamic dopaminergic mechanism (3). Other neurotransmitters, notably norepinephrine and serotonin, exert a modulating effect (4). Based on the studies showing that proestrus prolactin surge in the rat could be suppressed by either prazosin or clonidine, it has been suggested that norepinephrine may have a stimulatory role on prolactin secretion, since both pharmacologic agents will block noradrenergic function. Serotonin neuron is believed to stimulate the secretion of a prolactin-releasing factor. The observation that the prolactin secretion rate is at least three times higher in uremic patients suggests there may be a loss of the feedback inhibition of prolactin secretion, perhaps related to altered catecholamine metabolism in the hypothalamus (1). The phenomenon of dopamine resistance is interesting and suggests an independent pituitary defect. During dopamine infusion plasma prolactin levels fell by less than 10% in uremic patients, compared to 40% in normal controls and renal transplant recipients, a highly significThe International Journal Of Artificial Organs I Vol. 4 no. 4,1981 I p.p. 152-153 © by Wichtig Editore sri, 1981