Comparative proteomic analysis of tear fluid in Graves' disease with and without orbitopathy.

BACKGROUND: Graves' orbitopathy (GO) is a severe organ-specific autoimmune inflammatory ocular complication most often associated with Graves' disease (GD). Besides the cosmetic problems these patients develop, GO may also cause severe, sight-threatening complications. Additionally, GO complicates the treatment of patients with GD, making the identification of Graves patients at risk for eye disease before they develop symptoms a critical step in the clinical management and quality of life of these patients. The high concentration of proteins in tear fluid makes it an important source for studying potential protein biomarkers for GO. PATIENTS AND METHODS: The aim of this study was to quantitatively compare tear fluid from GD patients with moderate/severe GO (GO) and patients with GD without GO (controls) using untargeted quantitative proteomics based on dimethyl labelling in combination with two-dimensional liquid chromatography-mass spectrometry. RESULTS: Among the 1212 proteins identified, 16 showed significant alterations in abundance between the two groups. Thus, in this study, we reveal a number of novel dysregulated proteins in GO which may contribute to a better understanding of the disease. In particular, upregulation of lacrimal gland proteins such as lysozyme C, lacritin, antileukoproteinase and zinc-alpha-2-glycoprotein 1 suggests involvement of the lacrimal gland in the pathogenesis of GO. CONCLUSIONS: It remains to be elucidated whether some of these proteins can be used as markers for patients at risk for developing GO as well as useful indicators for disease activity.

Adrenal autoantibodies and organ-specific autoimmunity in patients with Addison's disease.

OBJECTIVE: Autoimmune destruction of the adrenal gland is the major cause of Idiopathic Addison's disease, but the significance of 21-hydroxylase autoantibodies and their correlation with the presence of other autoantibodies have not so far been investigated in a larger population of patients with Addison's disease. We have now characterized a cohort of patients with idiopathic Addison's disease (n = 97) regarding the specificity of autoantibodies against the adrenal cortex and, as Addison's disease can be either an isolated condition or part of a polyendocrine disorder, we investigated the presence of organ-specific polyendocrine autoimmunity in this patient population. DESIGN: Cross-sectional study. MEASUREMENTS: Autoantibodies were analysed with indirect immunofluorescence (IF) on tissue preparations, ELISA and in Western blots using bacterially expressed proteins. RESULTS: Eighty-four per cent (81/97) of the patient sera recognized the steroid-producing cells of the adrenal cortex in indirect IF. The antigen was identified as 21-hydroxylase by 72% (70/97) of the patient sera in Western blots. Seven sera that were negative on adrenocortical IF identified 21-hydroxylase on Western blot, while eight IF-positive sera were 21-hydroxylase-negative. Five sera weakly recognized 17 alpha-hydroxylase in Western blots, but all of these were also positive for 21-hydroxylase. In 13 cases (12 women), the sera also reacted with testicular Leydig cells, and nine of these identified the side-chain cleavage (SCC) enzyme. Other clinically evident organ-specific autoimmune disorders were present in 40% of the 97 patients and abnormal titres of organ-specific antibodies were found in 60% of the patients. CONCLUSIONS: In idiopathic Addison's disease, auto-antibodies against 21-hydroxylase are found in a majority of cases and this represents an important diagnostic tool. The enzyme 17 alpha-hydroxylase does not seem to constitute a major autoantigen in Addison's disease. In a subgroup of patients with autoantibodies to gonads, antibodies to SCC are produced, often in parallel with antibodies to 21-hydroxylase. In yet another subgroup the specificity of autoantibodies giving positive immunofluorescence is still unknown. Three patients revealed a polyendocrine syndrome which clinically resembles autoimmune polyendocrine syndrome (APS) type I, but serologically corresponds to APS type II. Polyendocrine disorders are often associated with Addison's disease, and screening, including quantification of autoantibodies, may help to identify those at risk of developing associated autoimmune disorders.

Immunoreactive tachykinins in 24-h collections of urine from patients with carcinoid tumours: characterization and correlation with plasma concentrations.

Tachykinins are a family of peptides that may be present in and secreted from carcinoid tumours of mid-gut origin. They are likely to play a role in the pathogenesis of, e.g. the flush, dyspnoea and valvular heart disease seen in the carcinoid syndrome. Since tachykinins are secreted from the tumour into the circulation in bursts, coinciding with flushing attacks, and have short half-lives, we anticipated that analysis of 24-h urine excretion of immunoreactive tachykinin metabolites might prove to be a more sensitive and stable parameter for monitoring than tachykinin-like immunoreactivity in plasma. The study included 48 patients hospitalized for treatment of advanced carcinoid tumours and 32 healthy controls. The urine excretion of tachykinin-like immunoreactive metabolites in the carcinoid patients (median 27.5 pmol 24 h-1, interquartile range (IQR) 8.5-51.0 pmol 24 h-1) was significantly (p<0.001) higher than that in the 32 healthy subjects (median 3.0 pmol 24 h-1, IQR 0.9-4.20 pmol 24 h-1). Of the patients, 38 (79%) had elevated 24-h urine excretion of tachykinin-like immunoreactive metabolites while 31 (64%) had elevated plasma concentrations of tachykinin-like immunoreactive metabolites. Of the patients, 27 (56%) had elevated concentrations of tachykinin-like immunoreactive metabolites both in plasma and urine, 12 (25%) had elevated concentrations only in urine excretion, 3 (6%) had elevated concentrations of only plasma tachykinin-like immunoreactive metabolites and 7 (14%) had elevation of neither plasma nor urine concentrations. Analysis by means of different column chromatographic techniques indicated that the immunoreactive material was heterogeneous, with some components co-eluting with oxidized neurokinin A (NKA) and neuropeptide K (NPK). The urine tachykinin-like immunoreactivity correlates well with that of plasma, but is a slightly more sensitive indicator of elevated tachykinin-like immunoreactivity, probably since levels of urine tachykinin-like immunoreactive metabolites reflect the overall amount of the latter secreted into the circulation during 24 h.

Modulation of beta-cell activity and its influence on islet cell antibody (ICA) and islet cell surface antibody (ICSA) reactivity.

Insulin-dependent diabetes mellitus (IDDM) is associated with the formation of autoantibodies against different antigens in the islets of Langerhans, so-called islet cell antibodies (ICA). The expression of a major autoantigen, the beta-cell specific enzyme glutamic acid decarboxylase (GAD), is glucose-dependent in vitro and correlated to insulin release in vitro. In this study the expression of islet autoantigens was examined in vivo and the relationship between beta-cell function and islet cell surface antibody (ICSA) reactivity was tested. Rats were fed for 10 days with glipizide or diazoxide, in order to stimulate or inhibit insulin release, respectively. Frozen sections of pancreata were incubated with ten ICA-positive IDDM sera and analyzed by indirect immunofluorescence. Two sera with a "beta-cell restricted" staining, five with an "all-islet cell" staining and three with a "mixed" pattern were employed. In all three groups, the highest end-point titres were obtained when pancreata of rats treated with glipizide were used. Intermediate titres were seen in control animals and the lowest titres were observed on pancreata from diazoxide-treated rats, regardless of the serum used. In contrast to these observations, no correlation between ICSA reactivity and islet cell activity could be demonstrated. Conflicting results concerning ICSA in previous reports and our failure to show a glucose regulation of ICSA reactivity, indicate that ICSA is a phenomenon with a low degree of specificity.(ABSTRACT TRUNCATED AT 250 WORDS)

Parathyroid function in relation to intestinal function and renal calcium reabsorption in patients with nephrolithiasis.

Recently a technique to measure intact parathyroid hormone (PTH), i.e. the biologically active hormone, has been available. The aim of the present study was to apply this method to evaluate the parathyroid function in a material of recurrent renal stone formers (n = 324). Intact PTH was found to be inversely related to both urinary calcium (r = -0.15; p less than 0.01) and serum calcium (p less than 0.02) indicating that in the majority of the patients with hypercalciuria this was accounted for by intestinal hyperabsorption and not by high serum PTH. Hyperabsorption was also the likely explanation for the finding of a positive relationship between the urinary calcium and oxalate excretions (r = 0.22; p less than 0.001) in medication-free patients without intestinal disorders, i.e. without enteric hyperoxaluria. Altogether 25 patients (7%) had elevated serum PTH concentrations. They were followed up with fasting serum and urinary electrolytes and an oral calcium loading test (1 g of calcium) in order to evaluate the importance of renal and intestinal factors responsible for the elevated serum PTH concentrations. The investigation was carried out on a free diet and on low and high calcium intakes, respectively. The incidence of intestinal malfunction, which was sometimes present without clinical symptoms, was found to be approximately the same as that of impaired renal conservation of calcium. The findings in the patients with intestinal malfunction were a reduced intestinal absorption of calcium and an enhanced tubular reabsorption of calcium (TRCa), with greater reabsorption of calcium for higher PTH values. In patients with impaired renal conservation of calcium despite the raised PTH there was no correlation between PTH and TRCa. When PTH was suppressed during the oral calcium load the TRCa was found to be inappropriately low and the renal defect obvious. The intestinal calcium absorption was secondarily increased to compensate for the renal losses.

Treatment of malignant midgut carcinoid tumours with a long-acting somatostatin analogue octreotide.

Treatment with the somatostatin analogue octreotide, SMS 201-995 (Sandostatin), has been carried out in a series of 23 patients with malignant midgut carcinoid tumours. The patients received initially 50 micrograms twice a day for six months, thereafter a median of 100 micrograms twice daily. Six of 22 evaluable patients (28%) showed objective tumour response lasting for 6 to 30 months. Stable disease was observed in 8 of the 22 patients (36%) and progressive disease in a further 8 patients (36%). A subjective response with decrease of diarrhoea or flushing was noted in 11 out of 22 patients (50%). Two out of 6 patients with objective response demonstrated a significant decrease of tumour size lasting for 6 and 30 months respectively. In order to maintain the clinical response, the dose had to be increased in all 6 responders. The adverse effects included development of diabetic blood glucose levels in 8 out of 22 patients (36%). Albumin-modified serum calcium levels were significantly reduced after treatment with octreotide 50 micrograms twice a day. One patient developed symptoms of hypocalcemia which was reversed by supplementation with calcium and D-vitamins. The somatostatin analogue SMS 201-995 has a beneficial effect in the treatment of patients with the carcinoid syndrome. However, the precise role of the drug in the long-term management of these patients has to be further investigated.

Treatment of malignant carcinoid tumors: a randomized controlled study of streptozocin plus 5-FU and human leukocyte interferon.

In a randomized controlled study, 20 patients with malignant carcinoid tumors were included. Ten patients received streptozocin plus 5-fluorouracil for 6 months and another 10 human leukocyte interferon (IFN). After 6 months of treatment, an objective tumor response was noted in five of the patients treated with IFN (50%) but in none of the patients on chemotherapy. Stable disease was found in five patients (50%) on IFN treatment and four (40%) on chemotherapy. Progressive disease was noted in six of the patients (60%) receiving chemotherapy. A statistical analysis using the chi-square test showed a significantly higher proportion of responders and stable disease in the IFN treated group (P = 0.0039). Furthermore, three of eight patients who had previously received chemotherapy showed later on an objective response to IFN. The objective responses were mainly noted in decreased tumor markers; however, two patients also showed a significant reduction of tumor size. Subjective responses were noted in 72% of patients treated with interferon, but only in 9% of those treated with streptozocin plus 5-fluorouracil. The results indicate that interferon treatment is superior to the combination of streptozocin plus 5-fluorouracil. Considering both the therapeutic effects and adverse reactions, human leukocyte interferon is a promising alternative for treatment of patients with malignant carcinoid tumors.

The effects of octreotide on basal and stimulated hormone levels in patients with carcinoid syndrome.

The carcinoid syndrome, a common feature of small intestinal carcinoid tumors with liver metastases, includes flushing, diarrhea, bronchoconstriction, and right heart failure. The etiology of the carcinoid syndrome is not well understood, but serotonin seems to be involved in the diarrhea, whereas tachykinins may play a role in the flush reaction. In a double blind placebo-controlled study, we studied the effect of octreotide in 20 patients with midgut carcinoid tumors and liver metastases. A sc injection of 50 micrograms octreotide caused a significant (P less than 0.001) decrease in median plasma tachykinins and serum pancreatic polypeptide, GH, and insulin for up to 4 h. Administration of octreotide (50 micrograms, twice daily, sc) caused a 26% decrease in urinary 5-hydroxyindoleacetia acid excretion, but the number of flushing attacks or bowel movements did not change significantly. A typical flush was provoked by pentagastrin, and plasma tachykinin and serotonin levels were measured. The flush reaction was graded on a 10-point visual analog scale. Octreotide (50 micrograms, sc) given 45 min before flush stimulation prevented tachykinin release completely and significantly reduced the median flushing score from 8.5 to 2. Placebo administered in the same way did not prevent tachykinin release after pentagastrin administration. Thus, octreotide prevents pentagastrin-induced flushing and the related hormonal changes in patients with the carcinoid syndrome.

Carcinoid heart disease: relationship of circulating vasoactive substances to ultrasound-detectable cardiac abnormalities.

Cardiac ultrasound investigation of 68 prospectively studied patients with histologically proven midgut carcinoid tumors showed right heart disease in 66%. The abnormal findings included morphologic and functional aberrations of the tricuspid valve in 52% and 83%, respectively, right atrial and ventricular enlargement in 53% and 30%, and paradoxical systolic septal contractions in 19%. The patients with the most pronounced right heart disease had significantly higher (p less than .01) plasma levels of the tachykinins neuropeptide K and substance P as well as higher (p less than .001) urinary excretion of the serotonin metabolite 5-hydroxyindoleacetic acid. These patients also had the most extensive tumor disease. The occurrence of echocardiographic abnormalities of the left heart was similar to that in healthy individuals of the same age, but abnormalities were less frequent among the patients with severe right heart disease. Electrocardiographic changes were nonspecific. Right heart disease thus seems to be present more often than previously reported in patients with malignant midgut carcinoid tumors. The severity of cardiac involvement does not seem to be related to the duration of carcinoid disease but more to the extent of the disease, i.e., higher plasma levels of serotonin and tachykinins.

Motilin in plasma and tumor tissues from patients with the carcinoid syndrome. Possible involvement in the increased frequency of bowel movements.

Motilin, normally present in a specific cell type in the upper small intestine, is believed to have a physiologic role in initiating the interdigestive migrating motor complex. Motilin may play a pathophysiologic role in the diarrhea in the irritable bowel syndrome, the dumping syndrome, chronic liver disease, and chronic renal failure. Furthermore, increased frequency of bowel movements is an important symptom in patients with the carcinoid syndrome. We have studied 73 patients with metastatic carcinoid tumors with regard to stool frequency and plasma concentration of motilin and neuropeptide K (NPK) and diurnal urinary excretion of 5-hydroxyindoleacetic acid (5-HIAA). Thirty-eight (52%) of the 73 patients had elevated (greater than 126 pmol/l) plasma concentrations of motilin, whereas 59 (81%) of the patients had diarrhea. The increased frequency of bowel motions correlated significantly (p less than 0.01) with the plasma concentrations of motilin, whereas no significant correlation with 5-HIAA and NPK was found. High-performance liquid chromatography of plasma extracts showed a single component eluting in the position of synthetic porcine motilin. However, extracts from five carcinoid tumors did not contain any significant levels of motilin. Carcinoid tumors are known to contain and secrete several biologically active substances such as serotonin, histamine, prostaglandins, and tachykinins, which are likely to cause disturbances of intestinal secretion and motility, which in turn might release motilin from the motilin-containing cells of the small intestine. The increased motilin levels might then participate in a vicious diarrhea circle together with the other agents.

Bronchoconstrictor and hypotensive effects in relation to pharmacokinetics of tachykinins in the guinea-pig--evidence for extraneuronal cleavage of neuropeptide K to neurokinin A.

1. The biological effects of the tachykinins substance P (SP), neurokinin A (NKA) and neuropeptide K (NPK) were studied in relation to their pharmacokinetic properties in the guinea-pig in vivo. 2. NKA and NPK exerted a considerably larger bronchoconstrictor effect than SP. The effect of NPK was slow in onset and had a long duration. The three tachykinins showed similar hypotensive effects although NPK had a longer duration of action than SP and NKA. 3. The disappearance of NPK-like immunoreactivity (-LI) from plasma after i.v. infusion of synthetic NPK was biphasic with apparent half-lives of 0.9 min and 6 min. The plasma half-life of NKA-LI was less than 2 min, while plasma SP-LI was degraded before biochemical analysis could be performed. 4. In guinea-pig plasma at 37 degrees C in vitro, NKA- and NPK-LI were stable for 10 min, while SP-LI disappeared with a half-life of 10 s. 5. Reversed phase HPLC analysis of plasma collected after an i.v. infusion of NPK for 25 min, indicated a partial cleavage of NPK into NKA. 6. It is concluded that potency of the biological effects of SP, NKA and NPK in the guinea-pig in vivo, may not only be attributed to activation of multiple tachykinin receptors but must also be related to the marked differences in pharmacokinetical properties between the tachykinins. Furthermore, whereas SP is rapidly degraded in plasma, NKA and NPK seem to be metabolized in other compartments.

Malignant carcinoid tumors. An analysis of 103 patients with regard to tumor localization, hormone production, and survival.

In a prospective study of 103 patients with carcinoid tumors consecutively referred for medical treatment, the most common sites of the primary tumors were the ileum (73%), bronchi (7%), and jejunum (4%). All patients had local metastases, and 96 (93%) also had liver metastases. The most common initial symptoms were diarrhea (32%), ileus (25%), and flush (23%). The overall frequency of diarrhea was 84% and of flush was 75%. Heart insufficiency caused by cardiac valve disease was seen in 33% of the patients. The carcinoid syndrome, including flush, diarrhea, and elevated urinary 5-hydroxyindole acetic acid (5-HIAA) concentrations, was manifested by 69 patients (67%), 64 of whom (93%) had carcinoid tumors of mid-gut origin. Elevated urinary 5-HIAA was found in 91 patients (88%), of which 89 displayed liver metastases. The plasma concentration of the tachykinin neuropeptide K (NPK) was elevated in 67 patients (66%), 63 of whom had tumors of the mid-gut region. Serum pancreatic polypeptide (PP) and human chorionic gonadotrophin alpha levels were elevated in 43% and 28% of the patients, respectively, and the highest levels were found in patients with metastatic bronchial carcinoid tumors. Thirty-nine of the 103 patients are now dead; 18 died of tumor progression, whereas 14 patients died of heart failure secondary to a carcinoid tricuspidal valve insufficiency. The estimated median survival from the time of histologic diagnosis was 14 years, and from the time of carcinoid syndrome was 8 years.

Isolation and characterization of neurokinin A, neurokinin A(3-10) and neurokinin A(4-10) from a neutral water extract of a metastatic ileal carcinoid tumour.

A metastasis to the right liver lobe of an argyrophil/argentaffin midgut carcinoid tumour in a patient with the classical carcinoid syndrome was examined for the presence of tachykinins other than substance P, using a specific antiserum. The extract was initially purified using SepPak cartridges, and subsequently subjected to cation-exchange chromatography on SP Sephadex C-25 which separated the immunoreactive material into two main components (components I and II). Both were further purified by anion-exchange chromatography on DEAE-Sephadex A-25, and by reverse-phase fast protein liquid chromatography. Component II was identified as neurokinin A by its immunochemical and chromatographic properties and amino acid sequence analysis. Component I consisted of two molecular forms which were identified as neurokinin A(3-10) and neurokinin A(4-10) by amino acid sequence analysis. The tumour tissue contained only small amounts of the eledoisin-like peptide that has earlier been demonstrated in mammalian tissues. Although this component behaved like the nonmammalian peptide eledoisin on reverse-phase HPLC and on reverse-phase ion-pair chromatography, eledoisin-specific antiserum E2 indicated that eledoisin-like peptide is not identical to eledoisin. Neurokinin A in carcinoid tumours has an N-terminal heterogeneity; this multiplicity constitutes a further support for the hypothesis that carcinoid tumours produce a number of tachykinins which may be present in different relative amounts in individual patients and may contribute to the individual differences in symptomatology.

Tachykinin production by carcinoid tumours in culture.

Tissue specimens from 5 patients with metastatic midgut carcinoid tumours were kept in organ culture for up to 6 months. The tumour cells were confined to the suspension in the form of condensed cell clusters and appeared to retain their endocrine characteristics. Radioimmunoassay for tachykinin immunoreactivity showed high concentrations in 4 out of 5 culture media. The concentrations were highest in the beginning of the experiment, but subsequently decreased. The 4 patients from which these tumours were taken had all elevated tachykinin concentrations in extracted plasma. The fifth culture medium had low tachykinin concentration, and the concentration in extracted plasma from this patient was within the normal range. Reversed-phase high-performance liquid chromatography of the culture media with elevated tachykinin concentrations revealed immunoreactive components with the characteristics of synthetic neuropeptide K, neurokinin A and eledoisin, components also found in plasma and tumour tissues of carcinoid patients. Our findings indicate that carcinoid tumour cells produce tachykinins. These peptides are biologically very active, resulting in flush and hypotension when infused intravenously into normals, and might contribute to the clinical symptoms of the carcinoid syndrome.

Cytotoxic treatment in patients with malignant carcinoid tumors. Response to streptozocin--alone or in combination with 5-FU.

Thirty-one patients with malignant carcinoid tumors were treated with streptozocin--alone (n = 7) or in combination with FU (n = 24). The responses to treatment were followed by the determination of tumor markers, urinary 5-HIAA, serum PP, HCG-alpha and -beta subunits, as well as determination of the size of liver metastases on computerized tomography or ultrasonography. Three patients (9.7%) showed objective responses with a mean remission time of 2.7 months. Eighteen patients (58%) showed stable disease, whereas ten patients (32.3%) showed progressive disease directly from the start of therapy. A good correlation was found between the changes in tumor markers and tumor size, although the changes occurred earlier in the markers than in the size. Estimated median survival from the time of histologically verified carcinoid tumor was 41 months and from start of therapy 22 months. Our data indicate that combination treatment with streptozocin and 5-fluorouracil is of little value for patients with malignant carcinoid tumors.

Treatment of malignant carcinoid tumors with human leukocyte interferon: long-term results.

Thirty-six patients with malignant carcinoid tumors were treated with human leukocyte interferon (IFN) im at doses of 3-6 megaunits/day. The origins of the primary tumors were as follows: mid-gut (29 patients); pulmonary (four); rectal (one); ovarian (one); and unknown (one). Nineteen of the 36 patients had previously been treated with cytotoxic agents, streptozocin plus 5-fluorouracil or doxorubicin, but showed progressive disease. With IFN objective tumor responses were seen in 17 of the 36 patients (47%): in 14 of the 29 patients with mid-gut carcinoids (48%) and in three of the four patients with lung carcinoids (75%). The median duration of response was 34 months. Stable disease was noted in 14 of 36 patients (39%), all presenting mid-gut carcinoids. The median duration of stable disease was 25 months. Progressive disease from the start of IFN therapy was seen in five patients (14%). All responders except one had a greater than 50% reduction of urinary 5-hydroxyindoleacetic acid or alpha-human chorionic gonadotropin, whereas four patients also had a significant reduction of tumor size on computerized tomographic scan or at laparotomy. Two patients achieved complete remission. Improvement of clinical manifestations of the carcinoid syndrome was seen in all patients with objective response. Adverse effects including influenza-like syndrome, reduction of blood cells, chemical signs of liver dysfunction, and disturbed lipid metabolism occurred but were reversible or could be circumvented by dose reduction. Autoimmune phenomena were also noted such as development of thyroid autoantibodies with thyroiditis, SLE syndrome with antinuclear factors, and parietal cell antibodies with pernicious anemia. IFN therapy seems to be very effective in controlling tumor-secreted substances and thus giving relief of clinical symptoms. It also arrests tumor growth for extended time periods (median, 2 years). The adverse effects are surmountable and less severe than with cytotoxic therapy.

Tachykinins in carcinoid tumors: their use as a tumor marker and possible role in the carcinoid flush.

The plasma concentrations of various tachykinins were measured before and during flushing episodes in 16 patients with metastatic carcinoid tumors. The flushing attacks were induced by iv injection of pentagastrin or ingestion of food or alcohol. Tachykinins, such as neurokinin A (NKA) and neuropeptide K (NPK), increased 2-fold during flushing episodes in 12 patients, and the plasma concentrations of substance P increased to a varying extent in 3 patients. Chromatographic analysis of plasma samples taken before and during flushing episodes in 2 patients indicated the presence of individual spectra of tachykinins. In addition, the plasma concentration of tachykinin [TKLI(K12)], using an assay that detects NKA, NPK, kassinin, eledoisin, and NKB, but not substance P and physalaemin, and the urinary excretion of 5-hydroxyindole acetic acid (5-HIAA) were measured in 20 patients with midgut carcinoid tumors before and during treatment with human leucocyte interferon. The overall changes in the 2 tumor markers were concordant in 18 of the 20 patients. Thus, the Spearman correlation coefficient between the percent changes in urinary 5-hydroxyindole acid excretion and plasma TKLI(K12) was 0.54 (P less than 0.001). The patients who had a decrease in the tumor markers also had a decrease in flushing episodes and diarrhea. Plasma TKLI(K12) is a convenient tumor marker for the diagnosis and follow-up of patients with carcinoid tumors of midgut origin. The combined use of both tumor markers strengthens the diagnosis and may improve the evaluation of response during treatment.