Dipeptidyl peptidase-4 inhibitors do not alter GH/IGF-I axis in adult diabetic patients

Purpose: Incretin-based therapies have been introduced in clinical practice for type 2 diabetes mellitus (T2DM) treatment in the last few years. Current available medications of this class include glucagon-like peptide 1 (GLP-1) receptor agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors. In addition to GLP-1, DPP-4 is able to inactivate many others peptides as hypothalamic growth hormone-releasing hormone (GHRH). The aim of this exploratory study was to evaluate, on adult diabetic patients, the impact of therapy with incretins, particularly DPP-4 inhibitors on GH/IGF-I axis. Methods: 60 patients with T2DM were included in the study and they were divided into three groups (age and sex comparable) on the basis of their hypoglycemic drugs in the last 4 months: group 1 (17 patients, exenatide or liraglutide + metformin), group 2 (18 patients, sitagliptin or vildagliptin + metformin), group 3 (25 patients, metformin). Anthropometric data, glycemia, glycosylated hemoglobin (HbA1c), IGF-I and acid-labile subunit (ALS) were collected in all patients. Results: Weight, waist circumference and BMI of group 1 were significantly higher (P < 0.05) compared to the other groups. Fasting plasma glucose and HbA1c of the group 1 were similar compared to those of group 3 (P ns) and higher compared to those of group 2 (P < 0.05). IGF-I absolute values, IGF-I SDS were not significantly different in the three groups. Conclusions: Our data evidence that DPP-4 inhibition does not influence significantly GH/IGF-I system, confirming what was observed in animal models. Further studies are needed to better characterize the properties of these molecules on endocrine system

Role of dopamine receptors in normal and tumoral pituitary corticotropic cells and adrenal cells

The recent depiction of dopamine receptors (DRs) in tumors that cause Cushing’s syndrome (CS) has renewed the debate about the dopamine control on pituitary-adrenal axis, and opened interesting new perspectives for medical treatment of CS. The new insights arise from the recent accurate characterization of DR subtypes expression within tumors causing CS, the discovery of new mechanisms, such as the dimerization between DRs and other G-protein coupled receptors (CPCRs), including somatostatin receptors (SSTRs), and the recent availability of new agents targeting these receptor subtypes. Corticotropic adenomas express DR subtype 2 (D&lt;sub&gt;2&lt;/sub&gt;R), together with different SSTR subtypes (ssts), in particular sst&lt;sub&gt;5&lt;/sub&gt;. In vitro, activation of D&lt;sub&gt;2&lt;/sub&gt;R inhibits ACTH release in the majority of cultures of corticotropic cells, whereas, in vivo, dopaminergic agents display an inhibitory effect on cortisol levels in a subset of patients with CS. In animal models the receptor profile can be deeply modulated in specific environmental conditions, that may resemble the different clinical phases of CS. The new insights about DRs and receptor-targeting drugs may offer different approaches for medical treatment of CS: combination therapies with different types of compounds, treatment with novel molecules (hybrid compounds) with a wider spectrum of activity, or even pretreatment manipulation of receptor profile. Finally, recent studies showed that D&lt;sub&gt;2&lt;/sub&gt;R is also significantly expressed in ectopic ACTH-secreting tumors and in both normal and tumoral adrenal tissues. Dopamine-agonists may decrease cortisol levels in a number of these patients, strengthening the current (re)emerging interest in DRs as possible targets for medical treatment of CS.</jats:p

The role of inferior petrosal sinus sampling in ACTH-dependent Cushing's syndrome:review and joint opinion statement by members of the Italian Society for Endocrinology, Italian Society for Neurosurgery, and Italian Society for Neuroradiology

In the management of adrenocorticotropic hormone (ACTH)-dependent Cushing's syndrome, inferior petrosal sinus sampling (IPSS) provides information for the endocrinologist, the neurosurgeon, and the neuroradiologist. To the endocrinologist who performs the etiological diagnosis, results of IPSS confirm or exclude the diagnosis of Cushing's disease with 80%-100% sensitivity and over 95% specificity. Baseline central-peripheral gradients have suboptimal accuracy, and stimulation with corticotropin-releasing hormone (CRH), possibly desmopressin, has to be performed. The rationale for the use of IPSS in this context depends on other diagnostic means, taking availability of CRH and reliability of dynamic testing and pituitary imaging into account. As regards the other specialists, the neuroradiologist may collate results of IPSS with findings at imaging, while IPSS may prove useful to the neurosurgeon to chart a surgical course. The present review illustrates the current standpoint of these 3 specialists on the role of IPSS