Pathophysiological study of diarrhoea in a patient with medullary thyroid carcinoma. Evidence against a secretory mechanism and for the role of shortened colonic transit time

Metastatic medullary thyroid carcinoma: a new way forward

Medullary thyroid carcinoma (MTC) is a rare malignancy comprising 1-2% of all thyroid cancers in the United States. Approximately 20% of cases are familial, secondary to a germline RET mutation, while the remaining 80% are sporadic and also harbour a somatic RET mutation in more than half of all cases. Up to 15-20% of patients will present with distant metastatic disease, and retrospective series report a 10-year survival of 10-40% from time of first metastasis. Historically, systemic therapies for metastatic MTC have been limited, and cytotoxic chemotherapy has demonstrated poor objective response rates. However, in the last decade, targeted therapies, particularly multitargeted tyrosine kinase inhibitors (TKIs), have demonstrated prolonged progression-free survival in advanced and progressive MTC. Both cabozantinib and vandetanib have been approved as first-line treatment options in many countries; nevertheless, their use is limited by high toxicity rates and dose reductions are often necessary. New generation TKIs, such as selpercatinib or pralsetinib, that exhibit selective activity against RET, have recently been approved as a second-line treatment option, and they exhibit a more favourable side-effect profile. Peptide receptor radionuclide therapy or immune checkpoint inhibitors may also constitute potential therapeutic options in specific clinical settings. In this review, we aim to present all current therapeutic options available for patients with progressive MTC, as well as new or as yet experimental treatments.

Endocrine paraneoplastic syndromes in patients with neuroendocrine neoplasms

OBJECTIVE

Our aim was to assess the prevalence of endocrine paraneoplastic syndromes (EPNS) in neuroendocrine neoplasms (NENs) and estimate its impact on patient outcomes.

DESIGN

This is a retrospective analysis of 834 patients with NENs (611 gastrointestinal, 166 thoracic, 57 of unknown and various other primary origin). We included 719 consecutive NEN patients treated at EKPA-Laiko Hospital, Athens, Greece and 115 patients with lung carcinoid (LC) treated at Uppsala University Hospital, Uppsala, Sweden. EPNS diagnosis was based on standard criteria.

METHODS

Twenty-one patients with EPNS were detected: 16 with ectopic Cushing's syndrome (ECS), one with hypercalcaemia due to parathyroid hormone-related protein (PTHrP) secretion, three with hypercalcitonaemia and one patient with dual secretion of calcitonin and beta-human chorionic gonadotropin (β-HCG). All tumours were well-differentiated; 10 patients had Stage IV disease at diagnosis.

RESULTS

The prevalence of EPNS in the Greek cohort was 1.9%, whereas that of ECS among LC patients in both centres was 6.7%. Median overall survival (OS) for patients with EPNS was 160.7 months (95%CI, 86-235.4) and median event-free survival (EFS) was 25.9 months (95%CI, 0-57.2). Patients presenting with EPNS prior to NEN diagnosis had longer EFS compared to patients with synchronous or metachronous EPNS (log-rank P = 0.013). Patients with ECS of extra-thoracic origin demonstrated shorter OS and EFS compared to patients with ECS of lung or thymic origin (log-rank P = 0.001 and P < 0.001, respectively). LC patients with and without ECS were comparable in 5-year and 10-year OS rates (66.7% and 33.3% versus 89.8% and 60.2%, respectively; 95%CI [189.6-300.4 months], log-rank P = 0.94) and in median EFS, 67 versus 183 months, 95%CI [50.5-207.5], log-rank P = 0.12).

CONCLUSION

EPNS are relatively rare in patients with NENs and mainly concern well-differentiated tumours of the foregut. Among patients with EPNS, LC-related ECS may not adversely affect patient outcomes when diagnosed prior to NEN and effectively been treated.

The management of neuroendocrine tumours: A nutritional viewpoint

Nutritional status in patients with neuroendocrine tumours (NETs), especially of gastroenteropancreatic origin, can be deeply affected by excessive production of gastrointestinal hormones, peptides, and amines, which can lead to malabsorption, diarrhoea, steatorrhea, and altered gastrointestinal motility. Besides, the surgical and/or medical management of NETs can lead to alteration of gastrointestinal secretory, motor, and absorptive functions, with both dietary and nutritional consequences. Indeed, disease-related malnutrition is a frequently encountered yet both underrecognized and understudied clinical phenomenon in patients with NETs, with substantial prognostic and socioeconomic consequences. Most of these conditions can be alleviated by a tailored nutritional approach, also with the aim of improving the efficacy of cancer treatments. In this setting, skilled nutritionists can play a fundamental role in the multidisciplinary health care team in NETs management and their presence should be recommended. The aim of this review is to provide dietary advices for each specific condition in patients with NETs, underlining the importance of a nutritional approach to treat malnutrition in this setting. Further, we will provide preliminary evidence coming from our data on the assessment of nutritional status in a single cohort of patients with NETs.

Efficacy of the Natural Clay, Calcium Aluminosilicate Anti-Diarrheal, in Reducing Medullary Thyroid Cancer-Related Diarrhea and Its Effects on Quality of Life: A Pilot Study

INTRODUCTION

Medullary thyroid cancer (MTC)-related diarrhea can be debilitating, reduces quality of life (QOL), and may be the only indication for initiating systemic therapy. Conventional antidiarrheal drugs are not always helpful and may have side effects. Calcium aluminosilicate antidiarrheal (CASAD), a natural calcium montmorrilonite clay, safely adsorbs toxins and inflammatory proteins associated with diarrhea. It was hypothesized that CASAD would reduce the severity of diarrhea and improve QOL in MTC patients.

METHODS

This was a prospective pilot trial (NCT01739634) of MTC patients not on systemic therapy with self-reported diarrhea of three or more bowel movements (BMs) per day for a week or more. The study design included a one-week run-in period followed by one week of CASAD ± a two-week optional continuation period. The primary endpoint was efficacy of one week of CASAD treatment in decreasing the number of BMs per day by ≥20% when compared with the baseline run-in period. Secondary objectives included tolerability and safety and the impact on QOL using the MD Anderson Symptom Inventory-Thyroid questionnaire (MDASI-THY).

RESULTS

Ten MTC patients (median age = 52 years, 70% female, 80% white) were enrolled. All had distant metastases, and median calcitonin was 5088 ng/mL (range 1817-42,007 ng/mL). Ninety percent had received prior antidiarrheals, and 40% of these had used two or more drugs, including tincture of opium (30%), loperamide (50%), diphenoxylate/atropine (20%), colestipol (10%), or cholestyramine (10%). Of seven evaluable patients, four (56%) had ≥20% reduction in BMs per day. Six out of seven patients discontinued their prior antidiarrheals. Best response ranged from 7% to 99% reduction in mean BMs/day from baseline. Five out of seven patients considered CASAD a success, and they opted for the two-week continuation period. Improvements in diarrhea and all six interference items assessed by MDASI-THY were noted at weeks 1 and 3. Total interference score was significantly improved at three weeks compared with baseline (p = 0.05). An oral levothyroxine absorption test was performed in one patient; malabsorption of levothyroxine was not observed. Adverse events included flatulence (40%), bloating (10%), heartburn (10%), and constipation (10%).

CONCLUSIONS

CASAD is a promising strategy for treatment of MTC-related diarrhea. In this small pilot study, improvements in frequency and quality of diarrhea as well as QOL were noted. Further studies in this population are warranted.

Thyroid disorders and gastrointestinal and liver dysfunction: A state of the art review

Thyroid disorders commonly impact on the gastrointestinal system and may even present with gastrointestinal symptoms in isolation; for example, metastatic medullary thyroid carcinoma typically presents with diarrhoea. Delays in identifying and treating the underlying thyroid dysfunction may lead to unnecessary investigations and treatment, with ongoing morbidity, and can potentially be life-threatening. Similarly, gastrointestinal diseases can impact on thyroid function tests, and an awareness of the concept and management of non-thyroidal illness is necessary to avoid giving unnecessary thyroid therapies that could potentially exacerbate the underlying gastrointestinal disease. Dual thyroid and gastrointestinal pathologies are also common, with presentations occurring concurrently or sequentially, the latter after a variable time lag that can even extend over decades. Such an association aetiologically relates to the autoimmune background of many thyroid disorders (e.g. Graves' disease and Hashimoto's thyroiditis) and gastrointestinal disorders (e.g. coeliac disease and inflammatory bowel disease); such autoimmune conditions can sometimes occur in the context of autoimmune polyglandular syndrome. Emphasis should also be given to the gastrointestinal side effects of some of the medications used for thyroid disease (e.g. anti-thyroid drugs causing hepatotoxicity) and vice versa (e.g. interferon therapy causing autoimmune thyroid dysfunction). In this review, we discuss disorders of the thyroid-gut axis and identify the evidence base behind the management of such disorders.

Revised American Thyroid Association guidelines for the management of medullary thyroid carcinoma

INTRODUCTION

The American Thyroid Association appointed a Task Force of experts to revise the original Medullary Thyroid Carcinoma: Management Guidelines of the American Thyroid Association.

METHODS

The Task Force identified relevant articles using a systematic PubMed search, supplemented with additional published materials, and then created evidence-based recommendations, which were set in categories using criteria adapted from the United States Preventive Services Task Force Agency for Healthcare Research and Quality. The original guidelines provided abundant source material and an excellent organizational structure that served as the basis for the current revised document.

RESULTS

The revised guidelines are focused primarily on the diagnosis and treatment of patients with sporadic medullary thyroid carcinoma (MTC) and hereditary MTC.

CONCLUSIONS

The Task Force developed 67 evidence-based recommendations to assist clinicians in the care of patients with MTC. The Task Force considers the recommendations to represent current, rational, and optimal medical practice.

Long-Term Follow-up in Medullary Thyroid Carcinoma

After surgery, patients with medullary thyroid carcinoma (MTC) should be assessed regarding the presence of residual disease, the localization of metastases, and the identification of progressive disease. Postoperatively, patients with MTC are staged to separate those at low risk from those at high risk of recurrence. The TNM staging system is based on tumor size, extra-thyroidal invasion, nodal metastasis, and distant spread of cancer. In addition, the number of lymph-node metastases, the number of compartments involved, and the postoperative calcitonin (CTN) and carcinoembryonic antigen (CEA) levels should be documented. The postoperative normalization of the serum CTN level is associated with a favorable outcome. When patients have basal serum CTN levels less than 150 pg/ml after a thyroidectomy, any persistent or recurrent disease is nearly always confined to lymph nodes in the neck. When the postoperative serum CTN level exceeds 150 pg/ml, patients should be evaluated with imaging procedures, including computed tomography (CT) of the neck and chest, contrast-enhanced magnetic resonance imaging (MRI) and ultrasound (US) of the liver, bone scintigraphy, MRI of the bone, and positron emission tomography (PET)/CT. One can estimate the growth rate of MTC metastases by quantifying increases in tumor size over time from sequential imaging studies analyzed with response evaluation criteria in solid tumors (RECIST), and by determining the tumor marker doubling time from sequential measures of serum CTN or CEA levels over multiple time points. One of the main challenges remains to find effective adjuvant and palliative options for patients with metastatic disease. Patients with persistent or recurrent MTC localized to the neck following thyroidectomy are candidates for neck operations, depending on the tumor extension. Once metastases appear, the clinician must decide which patients require therapy. This requires a balance between the (often) slow rate of tumor progression, which is associated with a good quality of life, and the limited efficacy and potential toxicities of local and systemic therapies. Considering that metastatic MTC is incurable, the management goals are to provide loco-regional disease control, palliate symptoms of hormonal excess, such as diarrhea, palliate symptomatic metastases, like pain or bone fracture, and control metastases that threaten life, such as bronchial obstruction or spinal cord compression. This can be achieved with palliative surgery, external beam radiation therapy (EBRT), or systemic therapy with tyrosine kinase inhibitor (TKI).

Diagnóstico, tratamento e seguimento do carcinoma medular de tireoide: recomendações do Departamento de Tireoide da Sociedade Brasileira de Endocrinologia e Metabologia

Introdução O carcinoma medular de tireoide (CMT) origina-se das células parafoliculares da tireoide e corresponde a 3-4% das neoplasias malignas da glândula. Aproximadamente 25% dos casos de CMT são hereditários e decorrentes de mutações ativadoras no proto-oncogene RET (REarranged during Transfection). O CMT é uma neoplasia de curso indolente, com taxas de sobrevida dependentes do estádio tumoral ao diagnóstico. Este artigo descreve diretrizes baseadas em evidências clínicas para o diagnóstico, tratamento e seguimento do CMT. Objetivo O presente consenso, elaborado por especialistas brasileiros e patrocinado pelo Departamento de Tireoide da Sociedade Brasileira de Endocrinologia e Metabologia, visa abordar o diagnóstico, tratamento e seguimento dos pacientes com CMT, de acordo com as evidências mais recentes da literatura. Materiais e métodos: Após estruturação das questões clínicas, foi realizada busca das evidências disponíveis na literatura, inicialmente na base de dados do MedLine-PubMed e posteriormente nas bases Embase e SciELO – Lilacs. A força das evidências, avaliada pelo sistema de classificação de Oxford, foi estabelecida a partir do desenho de estudo utilizado, considerando-se a melhor evidência disponível para cada questão. Resultados Foram definidas 11 questões sobre o diagnóstico, 8 sobre o tratamento cirúrgico e 13 questões abordando o seguimento do CMT, totalizando 32 recomendações. Como um todo, o artigo aborda o diagnóstico clínico e molecular, o tratamento cirúrgico inicial, o manejo pós-operatório e as opções terapêuticas para a doença metastática. Conclusões O diagnóstico de CMT deve ser suspeitado na presença de nódulo tireoidiano e história familiar de CMT e/ou associação com feocromocitoma, hiperparatireoidismo e/ou fenótipo sindrômico característico, como ganglioneuromatose e habitus marfanoides. A punção aspirativa por agulha fina do nódulo, a dosagem de calcitonina sérica e o exame anatomopatológico podem contribuir na confirmação do diagnóstico. A cirurgia é o único tratamento que oferece a possibilidade de cura. As opções de tratamento da doença metastática ainda são limitadas e restritas ao controle da doença. Uma avaliação pós-cirúrgica criteriosa para a identificação de doença residual ou recorrente é fundamental para definir o seguimento e a conduta terapêutica subsequente.

Vandetanib: opening a new treatment practice in advanced medullary thyroid carcinoma

Medullary thyroid cancer (MTC) is frequently diagnosed in a locally advanced or metastatic stage, and 10-year survival rates in these cases are below 20 %. Cytotoxic chemotherapy has no significant impact on overall or progression-free survival. Vandetanib (Caprelsa(®), AstraZeneca) is a once-daily oral tyrosine kinase inhibitor that selectively inhibits signalling mediated by growth-factor receptor tyrosine kinase RET (constitutively activated in roughly 60 % of all MTCs), vascular endothelial growth-factor receptors 2 and 3, and epidermal growth-factor receptors. It is the first systemic drug with demonstrated anti-tumor benefits in advanced MTC, and it has recently been approved for locally advanced or metastatic MTC by the United States Food and Drug Administration (April 2011) and the European Medicines Agency (February 2012). This review, starting from the phases II and III efficacy and safety data that led to these approvals, explores important issues related to dosing, patient selection, and strategies for managing the substantial risk of toxicity associated with the drug (including life-threatening cardiac events that are the subject of a black-box warning in the United States). All these issues still remain to be defined. Vandetanib is becoming a standard of care for symptomatic, progressive, metastatic MTCs, to be used selectively in those patients who are likely to benefit from it.

Calcitonin receptor-mediated CFTR activation in human intestinal epithelial cells

High levels of calcitonin (CT) observed in medullary thyroid carcinoma and other CT-secreting tumours cause severe diarrhoea. Previous studies have suggested that CT induces active chloride secretion. However, the involvement of CT receptor (CTR) and the molecular mechanisms underlying the modulation of intestinal electrolyte secreting intestinal epithelial cells have not been investigated. Therefore, current studies were undertaken to investigate the direct effects of CT on ion transport in intestinal epithelial cells. Real time quantitative RT-PCR and Western blot analysis demonstrated the expression of CTR in intestinal epithelial T84 cells. Exposure of T84 cells to CT from the basolateral but not from apical side significantly increased short circuit current (I_SC) in a dose-dependent manner that was blocked by 1 μM of CTR antagonist, CT8–32. CT-induced I_SC was blocked by replacing chloride in the bath solutions with equimolar gluconate and was significantly inhibited by the specific cystic fibrosis transmembrane conductance regulator (CFTR) inhibitor, CFTR_127inh. Further, biotinylation studies showed that CT increased CFTR levels on the apical membrane. The presence of either the Ca²⁺ chelator, bis(2-aminophenoxy)ethane tetraacetic acid-acetoxymethyl (BAPTA-AM) ester or the protein kinase A (PKA) inhibitor, H89, significantly inhibited I_SC induced by CT (∼32–58% reduction). Response to CT was retained after permeabilization of the basolateral or the apical membranes of T84 cells with nystatin. In conclusion, the activation of CTR by CT induced chloride secretion across T84 monolayers via CFTR channel and the involvement of PKA- and Ca²⁺-dependent signalling pathways. These data elucidate the molecular mechanisms underlying CT-induced diarrhoea.

2012 European thyroid association guidelines for metastatic medullary thyroid cancer

Distant metastases are the main cause of death in patients with medullary thyroid cancer (MTC). These 21 recommendations focus on MTC patients with distant metastases and a detailed follow-up protocol of patients with biochemical or imaging evidence of disease, selection criteria for treatment, and treatment modalities, including local and systemic treatments based on the results of recent trials. Asymptomatic patients with low tumor burden and stable disease may benefit from local treatment modalities and can be followed up at regular intervals of time. Imaging is usually performed every 6-12 months, or at longer intervals of time depending on the doubling times of serum calcitonin and carcinoembryonic antigen levels. Patients with symptoms, large tumor burden and progression on imaging should receive systemic treatment. Indeed, major progress has recently been achieved with novel targeted therapies using kinase inhibitors directed against RET and VEGFR, but further research is needed to improve the outcome of these patients.

Calcitonin-secreting pancreatic endocrine tumors: systematic analysis of a rare tumor entity

OBJECTIVE

Pancreatic endocrine tumors (PETs) are characterized by the presence of hormone syndromes. Reports focusing on calcitonin-secreting PET (CTsPETs) are very rare. This study aimed to define a CTsPET-associated syndrome in regard to chemical, anatomical, and developmental aspects.

METHODS

A computerized MEDLINE search was conducted under the search items: "pancreatic endocrine tumor," "calcitonin," "neuroendocrine pancreatic tumor," and "pancreas." Results of clinical, histopathological, immunohistochemical, and biochemical assessments of all patients identified with CTsPET were registered and statistically analyzed.

RESULTS

Thirty-seven patients with CTsPET were identified. Mean serum calcitonin was elevated to the 89.2-fold of the upper reference value. Main symptoms were watery diarrhea (51.4%) and abdominal pain (35.1%). Most patients (59.5%) presented with metastatic spread at the time of diagnosis. Of all patients, 66.7% were alive after a mean follow-up of 28.9 months. Survival was higher in patients who underwent more aggressive surgical therapies independent from tumor sizes and in those with no metastases at the time of diagnosis.

CONCLUSIONS

High calcitonin levels should always raise suspicion of medullary thyroid carcinomas. However, when thyroid examination remains without pathological findings, a CTsPET should be excluded. An aggressive surgical approach even in cases with large primary tumor sizes may lead to a longer survival.

The thyroid and the gut

Thyroid disease is common, and its effects on the gastrointestinal system are protean, affecting most hollow organs. Hashimoto disease, the most common cause of hypothyroidism, may be associated with an esophageal motility disorder presenting as dysphagia or heartburn. Dyspepsia, nausea, or vomiting may be due to delayed gastric emptying. Abdominal discomfort, flatulence, and bloating occur in those with bacterial overgrowth and improve with antibiotics. Reduced acid production may be due to autoimmune gastritis or low gastrin levels. Constipation may result from diminished motility, leading to an ileus, megacolon, or rarely pseudoobstruction. Ascites in myxedema is characterized by a high protein concentration. Graves' disease accounts for 60% to 80% of thyrotoxicosis. Hyperthyroidism is accompanied by normal gastric emptying with low acid production, partly due to an autoimmune gastritis with hypergastrinemia. Transit time from mouth to cecum is accelerated, resulting in diarrhea. Steatorrhea is due to hyperphagia and stimulation of the adrenergic system. Diarrhea in medullary carcinoma of the thyroid (MCT) may be due to elevated calcitonin, prostaglandins, or 5-hydroxyindoleacetic acid. Ileal or colonic function may be abnormal. The esophagus may be compressed by benign processes, but more often by malignancies. MRI and CT scans are the best diagnostic modalities. The gastrointestinal manifestations of thyroid disease are generally due to reduced motility in hypothyroidism, increased motility in hyperthyroidism, autoimmune gastritis, or esophageal compression by a thyroid process. Symptoms usually resolve with treatment of the thyroid disease.

Medullary thyroid cancer: management guidelines of the American Thyroid Association

BACKGROUND

Inherited and sporadic medullary thyroid cancer (MTC) is an uncommon and challenging malignancy. The American Thyroid association (ATA) chose to create specific MTC Clinical Guidelines that would bring together and update the diverse MTC literature and combine it with evidence-based medicine and the knowledge and experience of a panel of expert clinicians.

METHODS

Relevant articles were identified using a systematic PubMed search and supplemented with additional published materials. Evidence-based recommendations were created and then categorized using criteria adapted from the United States Preventive Services Task Force, Agency for Healthcare Research and Quality.

RESULTS

Clinical topics addressed in this scholarly dialog included: initial diagnosis and therapy of preclinical disease (including RET oncogene testing and the timing of prophylactic thyroidectomy), initial diagnosis and therapy of clinically apparent disease (including preoperative testing and imaging, extent of surgery, and handling of devascularized parathyroid glands), initial evaluation and treatment of postoperative patients (including the role of completion thyroidectomy), management of persistent or recurrent MTC (including the role of tumor marker doubling times, and treatment of patients with distant metastases and hormonally active metastases), long-term follow-up and management (including the frequency of follow-up and imaging), and directions for future research.

CONCLUSIONS

One hundred twenty-two evidence-based recommendations were created to assist in the clinical care of MTC patients and to share what we believe is current, rational, and optimal medical practice.

A calcitonin and vasoactive intestinal peptide-producing pancreatic endocrine tumor associated with the WDHA syndrome

BACKGROUND

Although pancreatic endocrine tumor can produce a variety of hormones, few pancreatic tumors produce a high systemic calcitonin concentration. Furthermore, calcitonin-producing pancreatic tumors rarely produce elevations of VIP in addition.

METHODS

We evaluated and treated a 50-yr-old woman with the WDHA syndrome. Abdominal computed tomography (CT) detected a tumor in the tail of the pancreas. Peripheral plasma calcitonin and VIP concentrations were markedly increased to 2000 pg/mL (normal, <74 pg/mL) and 7200 pg/mL (normal, <100 pg/mL), respectively. We diagnosed a calcitonin- and VIP-producing pancreatic endocrine tumor, which was removed by distal pancreatectomy including splenectomy.

RESULTS

Plasma calcitonin and VIP were determined in blood from the vein draining the tumor and splenic vein, sampled at operation. These secreted concentrations were extremely high: 4640 and 3610 pg/mL for calcitonin; 24700 and 13500 pg/mL for VIP. Calcitonin and VIP were also highly elevated in the resected tumor. Plasma calcitonin and VIP rapidly decreased after tumor resection. The patient has been well without recurrence for over 20 yr.

CONCLUSION

An unusual pancreatic tumor secreting vasoactive intestinal peptide (VIP) caused WDHA syndrome (watery diarrhea, hypokalemia, and achlorhydria/hypochlorhydria) and also hypercalcemia. The latter was only partially offset by a large excess of calcitonin also secreted by the tumor.

Phosphospecific site tyrosine phosphorylation of p125FAK and proline-rich kinase 2 is differentially regulated by cholecystokinin receptor type A activation in pancreatic acini

The focal adhesion kinases, p125FAK and proline-rich kinase 2 (PYK2), are involved in numerous processes as adhesion, cytoskeletal changes, and growth. These kinases have 45% homology and share three tyrosine phosphorylation (TyrP) sites. Little information exists on the ability of stimulants to cause TyrP of each kinase site and the cellular mechanism involved. We explored the ability of the neurotransmitter/hormone, CCK, to stimulate TyrP at each site. In rat pancreatic acini, CCK stimulated TyrP at each site in both kinases. TyrP was rapid except for pY397FAK. The magnitude of TyrP differed with the different FAK and PYK2 sites. The CCK dose-response curve for TyrP for sites in each kinase was similar. CCK-JMV, an agonist of the high affinity receptor state and antagonist of the low affinity receptor state, was less efficacious than CCK at each FAK/PYK2 site and inhibited CCK maximal stimulation. Thapsigargin decreased CCK-stimulated TyrP of pY402PYK2 and pY925FAK but not the other sites. GF109203X reduced TyrP of only the PYK2 sites, pY402 and pY580. GF109203X with thapsigargin decreased TyrP of pY402PYK2 and the three FAK sites more than either inhibitor alone. Basal TyrP of pY397FAK was greater than other sites. These results demonstrate that CCK stimulates tyrosine phosphorylation of each of the three homologous phosphorylation sites in FAK and PYK2. However, CCK-stimulated TyrP at these sites differs in kinetics, magnitude, and participation of the high/low affinity receptor states and by protein kinase C and [Ca2+]i. These results show that phosphorylation of these different sites is differentially regulated and involves different intracellular mechanisms in the same cell.

5-Hydroxytryptamine and functional bowel disorders

The possibility that 5-hydroxytryptamine (5-HT) acts as a key sensitising agent in the aetiology of irritable bowel syndrome (IBS) is reviewed. The strategic locations of 5-HT and its receptors are described, the most dominant being the 5-HT3 and 5-HT4 type. 5-HT, acting mostly at 5-HT3 or 5-HT3-like receptors, enhances the sensitivity of visceral neurones projecting between the gut and the central nervous systems. 5-HT, acting at 5-HT4 receptors promotes the sensitivity of enteric neurones that react to luminal stimuli. 5-HT4 and 5-HT3 receptors also mediate, respectively, sensitising and physiological actions of 5-HT on gastro-intestinal motor and secretory functions. This distribution implies that some 5-HT3 receptor antagonists might reduce certain symptoms of IBS, such as pain, by reducing the reactivity of the visceral afferent neurones linking the gut with the brain and spinal cord. However, such antagonists are not likely to find widespread clinical acceptance because they can also affect normal lower bowel function and promote constipation. 5-HT4 receptor antagonists, by contrast, reduce 5-HT-induced enteric nerve hypersensitivity without notably affecting the function of the normal bowel. Accordingly, these agents may reduce the symptoms of IBS directly, by reducing the incidence of defecation and diarrhoea and indirectly, by reducing both 'rebound' constipation and the post-prandial discomfort and pain associated with gastrointestinal hyper-reactivity.

Multiple endocrine neoplasia

The MEN syndromes continue to be the focus of considerable interest and research. Since successful treatment requires early diagnosis, proper screening and follow-up of patients at risk is important. In the individual at risk for developing MEN IIa, annual screening should include measurement of the basal and stimulated plasma CT levels, and determination of plasma levels of calcium, PTH, and CEA. Twenty-four hour urine excretion rates of norepinephrine, epinephrine, metanephrine, dopamine, and VMA should also be obtained. It is our recommendation that this screening be continued through the third decade of life. Patients having thyroidectomy for MTC need to be tested annually for recurrent MTC and the development of adrenal medullary disease. All patients at risk for developing MEN IIb should be evaluated in a similar fashion. Recently, several groups using DNA linkage analysis have mapped the gene for MEN IIa to chromosome 10, although the exact location of the gene is yet to be determined. Preliminary linkage studies have mapped the gene for MEN I to chromosome 11. The identification of the genes for MEN I and MEN II will greatly simplify the diagnosis of the disease and perhaps also the therapy of affected patients.