Serum gastrin and serum calcitonin in patients with chronic renal failure

Basal and Stimulated Calcitonin and Procalcitonin by Various Assays in Patients with and without Medullary Thyroid Cancer

BACKGROUND

Calcitonin (CT) is a sensitive marker for evaluation of medullary thyroid cancer (MTC). However, CT measurement can vary with assay- and nonassay-dependent factors, and procalcitonin (PCT) measurement has been proposed for evaluating questionable increases in CT.

METHODS

We tested 2 fully automated CT assays (Immulite [IL] and Liaison [LIA]) and 1 nonautomated CT assay (IRMA, Medipan) and compared these results with PCT (Brahms Kryptor). We evaluated preanalytical conditions and PCT cross-reactivity in sera of 437 patients with clinical conditions associated with hypercalcitoninemia. Additionally, we determined the true “nil” CT concentration in 60 thyroidectomized patients and defined CT cutoff concentrations for pentagastrin stimulation testing in 13 chronic kidney disease (CKD) patients and 10 MTC patients.

RESULTS

Markedly decreased CT concentrations were found after storage of sera for >2 h at room temperature and >6 h at 4 °C. Cutoff concentrations for basal and stimulated CT were disease and assay dependent. Proton pump inhibitor therapy was the most frequent reason for increased CT. PCT concentrations were higher in patients with MTC than in patients with CKD without infections (P < 0.001). Whereas IL and LIA demonstrated comparable analytical quality, the IRMA gave increased CT concentrations in nil sera and showed cross-reactivity with PCT in patients with concomitant bacterial infection.

CONCLUSIONS

IL, LIA, and IRMA detected increased CT concentrations in non-MTC patients and discriminated MTC from CKD patients in pentagastrin tests. PCT assessment may be helpful in the diagnostic work-up of increased CT concentrations in questionable clinical circumstances.

The effect of renal transplantation on basal serum gastrin concentration

Basal serum gastrin concentration was measured before and every week during the initial 5 weeks after renal transplantation in 9 of 20 patients with chronic renal failure who obtained a well functioning renal transplant. Furthermore, calcium and phosphorus metabolism in relation to serum gastrin was investigated in all 20 patients 5 weeks after transplantation. Before renal transplantation, serum gastrin was markedly elevated as compared with the levels in normal controls. During the first 3-5 weeks after renal transplantation, serum gastrin decreased towards normal values. A slight but significant increase in serum gastrin persisted 5 weeks after transplantation. No significant relation between changes in serum gastrin concentration and in calcium and phosphorus metabolism was observed.

Serum calcitonin in patients with chronic renal disease

The relationship between serum calcitonin, calcium-phosphorus metabolism and renal function was studied in 66 patients with chronic renal disease. Serum calcitonin was significantly elevated both in non-dialysed patients and in patients on chronic hemodialysis. In the non-dialysed patient group a highly significant inverse correlation was found between serum calcitonin and creatinine clearance. Between serum concentrations of calcitonin and phosphorus a significant positive correlation was found. In the dialysed patients a significant inverse correlation was found between serum calcium and serum calcitonin. It is concluded that the elevated serum calcitonin in patients with chronic renal disease might be explained by a reduced renal degradation of calcitonin and/or an increased production due to stimulation by serum phosphorus.

Pentagastrin testing in patients with renal insufficiency: normal responsivity of mature calcitonin

Calcitonin (CT) is the most sensitive tumor marker for medullary thyroid carcinoma available, but it lacks specificity. Chronic renal failure (CRF) is known to be associated with elevations of serum immunoreactive calcitonin. Using an immunoradiometric assay to detect only mature CT, we evaluated the basal CT level and its response to pentagastrin in 30 patients with CRF and compared these data with those obtained in 71 controls. Basal mature CT was significantly higher (p < 0.05) in patients with CRF (3.55 pg/mL) than in controls (2.00). Among these patients, 20% had basal CT levels more than 10 pg/mL with a maximum of 51 pg/mL. Peak CT values (highest value obtained 3 or 5 minutes after pentagastrin) were comparable in the two groups. Among patients with CRF, 10% had peak CT values greater than 30 pg/mL with a maximum of 53 pg/mL. In this group of patients, no correlation was found between CT (at any time during the test) and parathyroid hormone, calcium, phosphate, or creatinine clearance. Men had significantly higher CT values compared with women at each time point tested, including peak values. Patients with CRF, who have not yet undergone dialysis, have moderately elevated basal CT levels, but have normal pentagastrin-stimulated peak CT levels.

Plasma calcitonin in rats with renal failure

To study the effect of the kidney on blood calcitonin (CT), rats were made uremic by either total or partial nephrectomy or bilateral ligation of the ureters. Plasma CT concentrations were measured by radioimmunoassay before and after calcium infusion. Uremia induced by total or partial nephrectomy produced an increase in plasma CT. Rats had higher plasma CT levels (49.3 +/- 1.7 pg/ml, mean +/- SE) after total nephrectomy than after ureteral ligation (30.9 +/- 1.5 pg/ml) even though no significant difference was observed between the blood urea nitrogen (BUN) levels of these two groups. These results indicate that the kidney contributes to the degradation of CT.

High serum calcitonin levels in heroin addicts

An involvement of calcitonin in the mechanism of pain perception has recently been hypothesized. In order to collect information about the relationship between this hormone and well known analgesic substances such as opioids, we have studied the serum levels of calcitonin in a group of heroin addicts, finding higher average concentrations than in normal subjects of matched age and sex. In these addicts there were no severe signs of impaired renal or hepatic function, or alterations of the serum levels of calcium and phosphate. So we think that opioids, in a direct or indirect way, can stimulate the secretion of calcitonin.

Renal control of the peripheral uptake of exogenous gastrin in the dog

The extraction of plasma gastrin during intravenous infusion of exogenous hormone has been measured in the head, gastrointestinal tract, or kidney of dogs submitted to sham surgery, evisceration, or binephrectomy without or with subsequent kidney transplantation. A significant gastrin extraction was demonstrated not only in the kidney, but also in the head and in the gastrointestinal tract; moreover, plasma gastrin extraction in the head and the bowel was considerably reduced by binephrectomy and was brought back to control values after subsequent kidney transplantation. A non-specific effect of surgery and a variation in peripheral blood flow seem to be excluded. Thus a control by the kidney of the peripheral removal of blood gastrin is evidenced, the mechanism of which remains hypothetical.