Fractionated radiotherapy and radiosurgery in acromegaly: analysis of 352 patients from the German Acromegaly Registry.

BACKGROUND: If biochemical control of acromegaly is not achieved by operation and medication, radiotherapy may be indicated. OBJECTIVE: To describe fractionated radiotherapy (FRT) and stereotactic radiosurgery (SRS) regarding excess of IGF-1 and pituitary function. DESIGN AND METHODS: A retrospective analysis of 352 patients (4126 patient-years) from the German Acromegaly Registry was performed. Follow-up was 1.0-45.1 years after radiotherapy. Therapeutic success was defined by low or normal IGF-1 according to center-specific reference ranges without (= remission) or on (= controlled disease) suppressive medication. RESULTS: Time between radiotherapy and last follow-up was 13.0 ± 8.2 years for FRT (n = 233) and 8.9 ± 5.0 years for SRS (n = 119, P < 0.001). Median (IQR) basal growth hormone before radiotherapy was 6.3 (2.9-16.2) ng/mL for FRT and 3.5 (1.8-6.9) ng/mL for SRS (P < 0.001). Mean time in uncontrolled state was 3.0 years after FRT and 2.1 years after SRS (95% CI for the difference is 0.1 to 1.6 years, P = 0.021). The 10-year calculated remission rate was 48% for FRT and 52% for SRS (95% CI for the difference is -18 to 26% age points, P = 0.74) and the respective controlled disease rate was 23 and 26%. The odds ratio for adrenocorticotropic or thyreotropic insufficiency was 0.54 (95% CI: 0.30-1.00, P = 0.049) in SRS compared to FRT patients. CONCLUSION: Both after FRT and SRS about 75% of patients with acromegaly are in remission or controlled after 10 years. A slightly faster achievement of target values was observed after SRS. The rate of pituitary insufficiency in FRT patients is significantly higher.

Clinical Impact of the Current WHO Classification of Pituitary Adenomas.

WHO classifications should be used for comparing the results from different groups of pathologist and clinicians by standardized histopathological methods. Our present report describes the important parameters of pituitary adenoma pathology as demand of the WHO classification for correlation to endocrine data and prognosis. The combination of HE stain based structures with immunostainings for pituitary hormones allows subclassification of adenomas as the best method not only for correlations to clinical hyperfunctions but also for statements to the sensitivity of drug therapies (somatostatin analogs, dopamine agonists). GH-, PRL- and ACTH-secreting pituitary adenomas are further classified based on the size and number of their secretory granules by electron microscopy, or as is mostly the case nowadays by cytokeratin staining pattern, into densely and sparsely granulated. Granulation pattern may be considered for the prediction of treatment response in patients with GH-secreting adenomas, since the sparsely granulated subtype was shown to be less responsive to somatostatin analog treatment. For prognosis, it is important to identify aggressive adenomas by measurements of the Ki-67 index, of the number of mitoses, and of nuclear expression of p53. Among the criteria for atypical adenomas, high Ki-67 labeling index and invasive character are the most important adverse prognostic factors. Promising molecular markers have been identified that might supplement the currently used proliferation parameters. For defining atypical adenomas in a future histopathological classification system, we propose to provide the proliferative potential and the invasive character separately.

Emerging Histopathological and Genetic Parameters of Pituitary Adenomas: Clinical Impact and Recommendation for Future WHO Classification.

The review assesses immunohistochemical findings of somatostatin receptors and of metalloproteinases in different pituitary adenoma types and the significance of molecular genetic data. Current evidence does not support routine immunohistochemical assessment of somatostatin or dopamine receptor subtype expression on hormone-secreting or nonfunctioning pituitary adenomas. Further prospective studies are needed to define its role for clinical decision making. Until then we suggest to restrict membrane receptor profiling to individual cases or for study purposes. The problems of adenoma expansion and invasion are discussed. Despite partially contradictory publications, proteases clearly play a major role in permission of infiltrative growth of pituitary adenomas. Therefore, detection of at least MMP-2, MMP-9, TIMP-2, and uPA seems to be justified. Molecular characterization is important for familial adenomas, adenomas in MEN, Carney complex, and McCune-Albright syndrome and can gain insight into pathogenesis of sporadic adenomas.

Screening for Acromegaly in Patients with Carpal Tunnel Syndrome: A Prospective Study (ACROCARP).

Early diagnosis of acromegaly prevents irreversible comorbidities and facilitates surgical cure. Carpal tunnel syndrome (CTS) is common in acromegaly and patients have often undergone surgery for CTS prior to the diagnosis of acromegaly. We hypothesized that screening CTS-patients for acromegaly could facilitate active case-finding. We prospectively enrolled 196 patients [135 women, 56.9 (range 23-103) years] who presented with CTS for surgery. Patients were asked about 6 symptoms suggestive of acromegaly using a questionnaire calculating a symptom score (0-6 points), and insulin-like-growth factor 1 (IGF-1) was measured. If IGF-1 was increased, IGF-1 measurement was repeated, and random growth hormone (GH) and/or an oral glucose tolerance test (OGTT) with assessment of GH-suppression were performed. The mean symptom score was 1.7±1.3 points. Three patients reported the maximal symptom score of 6 points, but none of them had an increased IGF-1. There was no correlation between the symptom score and IGF-1-SDS (standard deviation score) (r=0.026; p=0.71). Four patients had an IGF-1>2 SDS. In 2 patients acromegaly was ruled out using random GH and OGTT. One patient had normal IGF-1 and random GH at follow-up. One patient refused further diagnostics. In this prospective cohort of patients with CTS, the observed frequency of acromegaly was at most 0.51% (95% CI 0.03 to 2.83%). In this prospective study, none of the 196 patients with CTS had proven acromegaly. Thus, we see no evidence to justify general screening of patients with CTS for acromegaly.

[Quality of life of young adults after a growth hormone therapy with childhood onset]. / Die Lebensqualität junger Erwachsener nach einer Wachstumshormonbehandlung im Kindesalter.

INTRODUCTION: Little is known about the health-related quality of life of young adults with childhood onset idiopathic growth hormone deficiency or neurosecretory dysfunction of growth hormone secretion, who have been treated with recombinant human growth hormone (GH). METHODS: Patients were diagnosed and treated with human growth hormone at the University Children´s Hospital in Erlangen (n=85). The data of both groups were merged for analysis, because no difference between idiopathic growth hormone deficiency and neurosecretory dysfunction of growth hormone secretion in auxological. Data were found. Health-related quality of life was cross- sectionally assessed after the end of growth hormone therapy with the Short Form-36 Health Survey and the Nottingham Health Profiles for which population based norm data are available. RESULTS: At the time of the survey, the patients (53 m, 32 f) were 23.5 ±â€…4.6 years old. At start of GH therapy, age was 10.5 ±â€…2.8 and at the end 16.3 ±â€…1,4 years. At start, height SDS was -3.20 ±â€…1.06. GH dose was 0,026 ±â€…0,012 mg/kg/d (daily s. c.-injections). The increase in height SDS after the end of GH therapy was 1.69 ±â€…1.22.  Compared to the reference population, patients reported significantly lower scores on the scales energy level, vitality, social functioning, indicating a greater social isolation, a stronger emotional reaction, an increased loss of mobility and a worse psychological state. CONCLUSION: Young adults report specific impairments after completion of GH therapy.

Hypophysitis caused by ipilimumab in cancer patients: hormone replacement or immunosuppressive therapy.

Ipilimumab is besides the BRAF inhibitor vemurafenib the first officially approved medical treatment for metastatic melanoma, which results in improved survival. Ipilimumab leads to a release of a CTLA4-mediated inhibition of T-cell immunoreactions. Therefore, patients may also suffer from immune-related adverse events affecting different organs, which are typically treated by high-dose corticosteroids. Ipilimumab-induced hypophysitis (iH) has been reported in up to 17% of melanoma patients in clinical trials.Here we present 5 patients with metastatic melanoma and 2 patients with prostate cancer who developed hypophysitis after ipilimumab therapy. Patients were treated by high-dose corticosteroid therapy resulting in the resolution of local inflammation but not of pituitary deficiencies. Partial or complete hypopituitarism remained in all patients. Pharmacotherapy with high-dose corticosteroids caused complications in 5 patients, necessitating hospitalization in 4. 2 of the 3 patients with progressive disease died, while 3 patients had stable disease and 1 patient showed tumor regression after discontinuation of ipilimumab.In summary, with regard to safety and simplicity of hormonal substitution therapy we have to scrutinize high-dose corticosteroid therapy, though it only improves inflammation but not neuro-endocrine function and may cause further morbidity. Regression of the tumor depends on the ipilimumab-mediated immune events, in which high-dose and long-term corticosteroid therapy for iH appears to be counter-intuitive. Herein, we discuss screening and the diagnostic as well as therapeutic management of iH in metastatic cancer patients from an endocrinologic perspective.

Levothyroxine medication is associated with adiposity independent of TSH.

AIM: In euthyroidism, higher TSH levels are weakly associated with increased BMI. Furthermore, a considerable number of patients complain of weight gain during thyroid hormone replacement after thyroidectomy. We therefore investigated the association between levothyroxine medication and BMI in a large cross-sectional study group. METHODS: We included euthyroid participants from the MeSyBePo study group (TSH between 0.3 and 4.5 µU/ml) that did not take thyreostatic drugs. Linear regression analyses were performed to address the association between levothyroxine medication and obesity. Additionally, pairs matched by sex, age and TSH but discordant in levothyroxine medication were compared. RESULTS: 1663 subjects (569 males) were eligible for inclusion. 151 participants were taking levothyroxine. Adjusted for sex and age both TSH (standardised beta 0.1, p<0.001) and levothyroxine medication (standardised beta 0.05, p=0.03) were significantly associated with BMI. There was no significant interaction between TSH and levothyroxine medication with respect to BMI. Further adjustment for smoking and the restriction to those subjects with normal glucose metabolism (947 participants (314 males, 82 on levothyroxine medication) did not alter the result. In matched pair analysis (133 pairs), BMI was significantly increased in subjects taking levothyroxine compared to controls. CONCLUSION: Independently from TSH, levothyroxine medication was associated with a higher BMI. The mechanisms, however, responsible for this association need to be elucidated.

Comparison of oral glucose tolerance test (OGTT) 100 g with OGTT 75 g for evaluation of acromegalic patients and the impact of gender on test reproducibility.

CONTEXT: Growth hormone (GH) measurements during an oral glucose tolerance test (OGTT) are essential for the diagnosis and follow-up management of acromegaly. However, both 100 g glucose (OGTT(100) ) and 75 g glucose (OGTT(75) ) test variants are in clinical use. Whether the tests are interchangeable concerning GH nadir and test interpretation is unclear. Furthermore, information on test reproducibility and the impact of gender is scarce. OBJECTIVE: To compare both tests in acromegalic patients and to evaluate test reproducibility with respect to gender. DESIGN, SUBJECTS AND METHODS: OGTT(100) and OGTT(75) were performed on two consecutive days in 54 acromegalic patients (46·9 ± 1·8 years, 30 women). OGTT(75) was repeated on three different occasions in 11 healthy men and 13 healthy women at different phases of the menstrual cycle. RESULTS: GH nadirs were comparable between tests [2·40 ± 0·52 (OGTT(100) ) and 2·46 ± 0·54 µg/l (OGTT(75) ); P = 0·356]. There were no differences at any time point in the mean values of GH, serum glucose or insulin between the two test variants. Test interpretation was highly consistent between the OGTT(100) and OGTT(75) [area under the receiver operated curve (ROC) = 0·995]. In men, GH, insulin and glucose measurements during OGTT(75) were highly reproducible. In women, however, basal and GH nadirs were significantly higher midcycle (P < 0·05). CONCLUSIONS: In acromegalic patients, there is no difference in GH nadirs and test interpretation after the ingestion of 100 g or 75 g glucose. The OGTT(75) is highly reproducible in men, but in women, it should be performed preferably in the early follicular phase.

T3/rT3-ratio is associated with insulin resistance independent of TSH.

Thyroid dysfunction has been shown to be associated with insulin resistance (IR). This may involve peripheral thyroid hormone metabolism, which is assumed to be reflected by the ratio triiodothyronine/reverse triiodothyronine (T3/rT3-ratio). To explore a potential association between the T3/rT3-ratio and IR we investigated pairs which differed in IR, but were matched by sex, age, body mass index (BMI), and thyroid stimulating hormone (TSH). For this purpose, matched pair analyses were embedded into a cross sectional study group. 22 pairs were matched from either the first or the third tertile of HOMA%S of a cohort of 353 euthyroid subjects with normal glucose metabolism who did not take any medication. The T3/rT3-ratio was compared in the matched pairs. The T3/rT3-ratio was significantly increased in the insulin resistant subjects compared to their insulin sensitive partners (8.78 ± 0.47 vs. 7.33 ± 0.33, p=0.019). Furthermore the T3/rT3-ratio was lower in men compared to women (p for the within-subject effect=0.046) both in the insulin sensitive and the insulin resistant subjects. Here we show that the T3/rT3-ratio, which is supposed to reflect the tissue thyroid hormone metabolism, is significantly increased in insulin resistant subjects. This further supports a link between thyroid function and IR.

Improved insulin sensitivity, preserved beta cell function and improved whole-body glucose metabolism after low-dose growth hormone replacement therapy in adults with severe growth hormone deficiency: a pilot study.

AIMS/HYPOTHESIS: Growth hormone-deficient patients show deterioration of insulin sensitivity and beta cell function. High-dose growth hormone treatment often induces further impairment of insulin sensitivity, leading to an increase in insulin and glucose levels or even, in cases of preexisting beta cell defect, to overt diabetes. However, low-dose treatment may improve insulin sensitivity, although data in humans with detailed metabolic phenotyping are as yet not available. We postulated that long-term low-dose growth hormone replacement, restoring IGF-1 to the low-normal range, might beneficially affect glucose metabolism. METHODS: We studied prospectively the metabolic responses to 24 and 48 weeks of growth hormone treatment in a small group of six adults with severe growth hormone deficiency (four men, two women; age 40-59 years; BMI 30.2 +/- 1 kg/m(2); mean growth hormone dose 0.3 +/- 0.04 mg/day). All participants underwent an oral glucose tolerance test, euglycaemic-hyperinsulinaemic clamp and hyperglycaemic-hyperinsulinaemic clamp plus i.v. L: -arginine on three occasions. Insulin sensitivity was measured by calculating the M value during the steady state of the euglycaemic-hyperinsulinaemic clamp. Insulin secretion and clearance were estimated from AUC(C-peptide), AUC(insulin) and their ratio at each phase of the hyperglycaemic-hyperinsulinaemic clamp. RESULTS: Growth hormone significantly improved insulin sensitivity (M value 13.8 +/- 2.6 [baseline] vs 19.6 +/- 2.6 [24 weeks] and 23.7 +/- 1.9 [48 weeks] micromol kg(-1) min(-1); p < 0.01). Although the insulin response to glucose and arginine decreased slightly, the disposition index, integrating insulin sensitivity and secretion, significantly increased (p < 0.01), indicating an improvement in whole-body glucose metabolism. Insulin clearance was not affected during treatment (p > 0.05). CONCLUSIONS/INTERPRETATION: Our data indicate that long-term low-dose growth hormone treatment may improve insulin sensitivity and whole-body glucose metabolism in adults with severe growth hormone-deficiency.

[Congenital adrenal hyperplasia and growth hormone deficiency. Special care in transition to adulthood]. / Adrenogenitales Syndrom und Wachstumshormonmangel. Betreuung beim Ubergang zum Erwachsenenalter.

Children with chronically endocrine diseases should be treated as young adults by adult endocrinologists. To optimize the transfer from the pediatric to adult endocrinologist, the model of a common transition clinic has been developed. Within this setting it should be possible to exchange experiences, extend the knowledge and understanding of the disease with the other side, and to provide for the patient an optimal outpatient care. This model, however, has only been sporadically realized to date. To set an example for the problems of the transition into adult endocrinology, we used two different endocrine diseases, the classical congenital adrenal hyperplasia due to 21-hydroxylase deficiency, and the childhood-onset growth hormone deficiency. Specific problems for this transfer to adult care are the fixation of the patients to their pediatricians and the lack of comprehension in the need of a long term and continuous therapy. The consequence is a dramatic impairment in the quality of the therapy.

Thyroid-stimulating hormone is associated with insulin resistance independently of body mass index and age in women with polycystic ovary syndrome.

BACKGROUND: The aim of this study was to evaluate the association between thyroid function, reflected by thyroid-stimulating hormone (TSH) levels, and insulin resistance (IR) in 337 women suffering from polycystic ovary syndrome (PCOS). METHODS: Clinical, metabolic and endocrine parameters were obtained and an oral glucose tolerance test was performed, with calculation of IR indices. The association between thyroid function and IR was evaluated with classification analysis using logistic regression and 10-fold cross-validation to identify a possible TSH threshold for IR. Parameters were then compared between women above and below the TSH threshold using two-sample tests. One-way analyses of covariance were performed to explore whether the impact of TSH on IR is independent of other variables. RESULTS: A TSH cut-off value around 2 mIU/l had the best sensitivity and specificity for identifying women with IR. Women with TSH >or= 2 mIU/l were younger, had a higher body mass index (BMI) and were more insulin-resistant compared with women with TSH < 2 mIU/l. This effect of TSH on IR was independent of age and BMI. CONCLUSIONS: In women with PCOS, a significant association between thyroid function, as reflected by TSH >or= 2 mIU/l, and IR was found and the association appeared to be independent of age and BMI.

Euglycemic hyperinsulinemia differentially modulates circulating total and acylated-ghrelin in humans.

Ghrelin is a powerful orexigenic gut hormone. Circulating concentrations of total ghrelin are downregulated by food intake in both acute and chronic hyperinsulinemic states. However, in blood des-acylated (des-acyl) ghrelin is the predominant form that has no orexigenic effects in humans. Circulating acyl-ghrelin has been shown to be suppressed post-prandially and by pharmacological hyperinsulinemia. However, up to now responses of circulating acyl-ghrelin to moderate hyperinsulinemic and hyperinsulinemic-hyperlipidemic clamp conditions have not been reported. Fourteen healthy subjects were investigated using two-stepped euglycemic-hyperinsulinemic clamps (40 mU insulin/ m2/min; mean 148+/-7 min till steady state, followed by 300 min lipid/heparin infusion). Responses of total ghrelin and acyl-ghrelin were measured at timed intervals throughout the clamps. Des-acyl-ghrelin concentrations were calculated by subtraction. Total ghrelin significantly decreased vs baseline concentrations (819+/-92 vs 564+/-58 pg/ml, p<0.001), thereby confirming previous observations. Des-acyl ghrelin closely followed total ghrelin concentrations and significantly decreased vs baseline (772+/-92 vs 517+/-56 pg/ml, p<0.001). In contrast, neither euglycemichyperinsulinemia nor euglycemic-hyperinsulinemic- hyperlipidemia suppressed acyl-ghrelin below baseline concentrations throughout the clamps (46+/-3 vs 47+/-8 pg/ml, p=0.90). In conclusion, moderate hyperinsulinemic and hyperinsulinemic- hyperlipidemic clamp conditions differentially modulated circulating total ghrelin and acylghrelin in humans. Factors other than changes in insulin and lipid concentrations are likely to contribute to the previously reported post-prandial reduction of circulating acyl-ghrelin.

Effects of euglycemic hyperinsulinemia and lipid infusion on circulating cholecystokinin.

AIMS: Functions of the gut hormone cholecystokinin (CCK) include an important role in the regulation of gastric emptying, postprandial glucose homeostasis, and postmeal satiety. Postprandial CCK responses are significantly blunted in type 2 diabetic patients by unknown mechanisms. We hypothesized that hyperinsulinemia and lipid infusion influence circulating levels of biologically active CCK. METHODS: Eleven healthy subjects were studied in a cross-over design after 10-h overnight fasts, using euglycemic-hyperinsulinemic clamps for 443 min, with an additional infusion of lipid-heparin (1.25 ml.min(-1)) or saline (1.25 ml.min(-1)) for the last 300 min after constant plasma glucose levels were achieved. RESULTS: Euglycemic-hyperinsulinemia resulted in a sustained, up to 5-fold increase of plasma CCK (P < 0.001). When adding lipid infusion instead of saline, CCK concentrations rapidly declined and returned to baseline levels (CCK(300 min) 1.1 +/- 0.2 vs. 3.3 +/- 0.3 pmol/liter, P < 0.001). Partial intraclass correlation showed an independent correlation of plasma CCK with free fatty acids (r(ic) = -0.377, P < 0.001) but not with serum insulin (r(ic) = 0.077, P = 0.32). Whole-body insulin sensitivity decreased in lipid-exposed subjects (M value 7.1 +/- 0.7 vs. 5.6 +/- 0.9 mg.kg.min(-1), P = 0.017) but was not independently correlated with CCK (r(ic) = 0.040, P = 0.61). CONCLUSIONS: We report novel findings showing that circulating CCK markedly increased in the euglycemic-hyperinsulinemic state, possibly as a result of near-complete suppression of circulating free fatty acids. Moreover, raising blood lipids even moderately by lipid infusion rapidly and significantly interfered with this effect, suggesting that a negative feedback mechanism of blood lipids on circulating CCK might exist.

Making sense of muscle fatigue and liver lesions.

Muscle weakness is a common complaint in clinical practice. If this symptom is combined with focal liver lesions there is a broad spectrum of differential diagnoses for the gastroenterologist to consider. Tumors of neuroendocrine origin such as small-cell lung carcinoma (SCLC) produce a wide array of peptide hormones and are common causes of paraneoplastic syndromes. We report on a 68-year-old woman who presented with progressing muscle fatigue and multiple liver lesions on ultrasonography. Hypertension, hyperglycemia, hypokalemia and metabolic alkalosis prompted consideration of underlying hypercortisolism. Further work-up demonstrated an acute ectopic ACTH syndrome as paraneoplastic manifestation of a small cell lung carcinoma. The woman deteriorated rapidly and finally died from intracranial tumor spread and septic complications. This case stresses the diagnostic and therapeutic difficulties of acute ectopic ACTH syndrome in the setting of SCLC.

Predicting impaired glucose metabolism in women with polycystic ovary syndrome by decision tree modelling.

AIMS/HYPOTHESIS: Polycystic ovary syndrome (PCOS) is a risk factor of type 2 diabetes. Screening for impaired glucose metabolism (IGM) with an OGTT has been recommended, but this is relatively time-consuming and inconvenient. Thus, a strategy that could minimise the need for an OGTT would be beneficial. MATERIALS AND METHODS: Consecutive PCOS patients (n=118) with fasting glucose <6.1 mmol/l were included in the study. Parameters derived from medical history, clinical examination and fasting blood samples were assessed by decision tree modelling for their ability to discriminate women with IGM (2-h OGTT value >/=7.8 mmol/l) from those with NGT. RESULTS: According to the OGTT results, 93 PCOS women had NGT and 25 had IGM. The best decision tree consisted of HOMA-IR, the proinsulin:insulin ratio, proinsulin, 17-OH progesterone and the ratio of luteinising hormone:follicle-stimulating hormone. This tree identified 69 women with NGT. The remaining 49 women included all women with IGM (100% sensitivity, 74% specificity to detect IGM). Pruning this tree to three levels still identified 53 women with NGT (100% sensitivity, 57% specificity to detect IGM). Restricting the data matrix used for tree modelling to medical history and clinical parameters produced a tree using BMI, waist circumference and WHR. Pruning this tree to two levels separated 27 women with NGT (100% sensitivity, 29% specificity to detect IGM). The validity of both trees was tested by a leave-10%-out cross-validation. CONCLUSIONS/INTERPRETATION: Decision trees are useful tools for separating PCOS women with NGT from those with IGM. They can be used for stratifying the metabolic screening of PCOS women, whereby the number of OGTTs can be markedly reduced.

Glucagon suppression of ghrelin secretion is exerted at hypothalamus-pituitary level.

CONTEXT: The mechanisms underlying the well-known glucagon-induced satiety effect are unclear. Recently, we showed that glucagon induces a remarkable decrease in the orexigenic hormone ghrelin that might be responsible for this effect. OBJECTIVE: The objective of this study was to evaluate the putative role of the hypothalamic pituitary axis in glucagon's suppressive effect on ghrelin secretion. DESIGN, SUBJECTS, AND METHODS: Prospectively, we studied the endocrine and metabolic responses to im glucagon administration in 22 patients (16 males; age, 21-68 yr; body mass index, 28.1 +/- 1.1 kg/m(2)) with a known hypothalamic-pituitary lesion and at least one pituitary hormone deficiency. Control experiments were performed in 27 healthy subjects (15 males; age, 19-65 yr; body mass index, 25.5 +/- 0.9 kg/m(2)). RESULTS: The suppression of ghrelin by glucagon measured as area under the curve(240 min) was significantly greater in controls when compared with patients (P < 0.01). Although there was a significant decrease in ghrelin in controls (P < 0.001), ghrelin was almost unchanged in patients (P = 0.359). Changes in glucagon, glucose, and insulin levels were comparable between both groups. CONCLUSIONS: We show that the hypothalamic-pituitary axis plays an essential role in the suppression of ghrelin induced by im glucagon administration. Glucagon significantly decreases ghrelin levels in healthy subjects. However, in the absence of an intact hypothalamic-pituitary axis, this effect was abolished. The mechanisms responsible for our observation are unlikely to include changes in glucose or insulin levels.

Wnt-5a has tumor suppressor activity in thyroid carcinoma.

Stabilization of beta-catenin by inhibition of its phosphorylation is characteristic of an activation of the canonical Wnt/beta-catenin signaling pathway and is associated with various human carcinomas. It contrasts to an as yet incompletely characterized action of an alternative noncanonical Wnt signaling pathway on neoplastic transformation. The aim of the present study was to test the effects of a member of the noncanonical Wnt signaling pathway, Wnt-5a, in primary thyroid carcinomas and in thyroid carcinoma cell lines. Compared to normal tissue Wnt-5a mRNA expression was clearly increased in thyroid carcinomas. Immunohistochemically, a bell-shaped response was observed with low to undetectable levels in normal tissue and in anaplastic tumors whereas differentiated thyroid carcinomas showed strong positive immunostaining for Wnt-5a. Transfection of Wnt-5a in a thyroid tumor cell line FTC-133 was able to reduce proliferation, migration, invasiveness and clonogenicity in these cells. These effects of Wnt-5a are associated with membranous beta-catenin translocation and c-myc oncogene suppression and are mediated through an increase in intracellular Ca(2+) release, which via CaMKII pathways promotes beta-catenin phosphorylation. Specific inhibition of beta-catenin phosphorylation by W-7, a calmodulin inhibitor, or by KN-93, a CaMKII inhibitor, supports these findings whereas PKC inhibitors were without effect. This interaction occurs downstream of GSK-3 beta as no Wnt-5a effect was seen on the Ser(9) phosphorylation of GSK-3 beta. Our data are compatible with the hypothesis that Wnt-5a serves as an antagonist to the canonical Wnt-signaling pathway with tumor suppressor activity in differentiated thyroid carcinomas.

Precision of intracellular calcium spike timing in primary rat hepatocytes.

Extracellular stimuli are often encoded in the frequency, amplitude and duration of spikes in the intracellular concentration of calcium ([Ca2+]i). However, the timing of individual [Ca2+]i-spikes in relation to the dynamics of an extracellular stimulus is still an open question. To address this question, we use a systems biology approach combining experimental and theoretical methods. Using computer simulations, we predict that more naturalistic pulsed stimuli generate precisely-timed [Ca2+]i-spikes in contrast to the application of constant stimuli of the same dose. These computational results are confirmed experimentally in single primary rat hepatocytes upon alpha1-adrenergic stimulation. Hormonal signalling in analogy to neuronal signalling thus has the potential to make use of temporal coding on the level of single cells. The [Ca2+]i-signalling cascade provides a first example for increasing the information capacity of an intracellular regulatory signal beyond the known coding mechanisms of amplitude (AM) and frequency modulation (FM).

Noise enhanced hormonal signal transduction through intracellular calcium oscillations.

In a wide range of non-linear dynamical systems, noise may enhance the detection of weak deterministic input signals. Here, we demonstrate this phenomenon for transmembrane signaling in a hormonal model system of intracellular Ca(2+) oscillations. Adding Gaussian noise to a subthreshold extracellular pulsatile stimulus increased the sensitivity in the dose-response relation of the Ca(2+) oscillations compared to the same noise signal added as a constant mean level. These findings may have important physiological consequences for the operation of hormonal and other physiological signal transduction systems close to the threshold level.