Renal and parathyroid function in psychiatric patients on lithium treatment

Abstract

Aims. To investigate the prevalence and clinical implications of renal and parathyroid morbidity in lithium patients. Patients. Short-term lithium patients (n=162; average 6 treatment years) and long-term patients (n=142; average 19 treatment years) were studied cross-sectionally. Forty-six short-term and thirteen long-term patients discontinued lithium for mean 18 and 8 weeks, respectively, and were compared to psychiatric controls. Of the short-term patients, 149 were followed-up in a medical record review after about 10 years. Methods. Urinary concentrating capacity (Umax), glomerular filtration rate (GFR), 24 hour urinary output (Uvol), total serum calcium and albumin were measured. Questionnaires and medical records provided additional data. Umax and GFR were compared with age-corrected reference values, prevalence and incidence with normal population data.Results. Short-term patients: 17% had reduced Umax, 16% Uvol ³3,000 ml, 4% ³5,000 ml; 8% reduced GFR, none uremia. Umax was inversely correlated with lithium treatment time. Lithium withdrawal caused an increase in Umax (p<0.001), Uvol (p<0.001), and GFR (p<0.05). Compared to controls, differences were insignificant. At follow-up, 14% were deceased, 28% without lithium. Among patients still on lithium (58%), reduced Umax was more common (38%) compared to 10 years before (14%; p<0.001) as was reduced GFR (21% vs. 10%; N.S). Long-term patients: 44% had reduced Umax, 12% nephrogenic diabetes insipidus, 40% Uvol ³3,000 ml (out of 86 patients measured), 18% ³5,000 ml; 21% reduced GFR, none uremia. Both thirst and polyuria indicated reduced Umax. Lithium withdrawal caused no change in Umax or Uvol. GFR increased by 7% (p=0.04). Compared to controls the irreversible Umax reduction was clinically relevant (mean difference 220 mosm/kg H2O = 26%; p=0.008), the GFR reduction was not (mean difference 4 ml/min/1.73 m2; p=0.81). In-patient treatment consumption was higher in patients with than without Umax reduction. Cardiovascular disease was more common among patients with than without GFR reduction.Hypercalcemia and surgically verified hyperparathyroidism were 2-4 times as common as expected. Total serum calcium was increased, compared to controls.Conclusions. Lithium nephropathy becomes more common with treatment time. Polyuria and reduced GFR entail an increased risk of lithium intoxication. The risk of hypercalcemia, and of hyperparathyroidism are increased.