The Latest Developments of Functional Molecular Imaging in the Diagnosis of Primary Aldosteronism.

Differentiation of unilateral from bilateral aldosterone hypersecretion is the essential step in the clinical practice of primary aldosteronism (PA). Although adrenal venous sampling (AVS) has been established as the most standard test recommended by the guideline, its invasive and technically difficult nature has facilitated the approach to develop non-invasive functioning imaging as an alternative test. Compared to the conventional adrenocortical scintigraphy with cholesterol derivatives as tracer, the first-generation imaging, both of 11C-MTO/PET and 123I-IMTO/SPECT/CT, the second-generation imaging, bind with high specificity and affinity to CYP11B enzymes and have advantages in shortening the time for obtaining specific images, reducing the radiation exposure to the patient, and resolution of the images. Because of very short half-life of 11C-MTO, 123I-IMTO has a potential for a wider application than 11C-MTO. Sensitivity of identifying an adenoma smaller than 1 cm in diameter is still a common limitation of these new functional imaging methods. The new functional imaging could be supplementary to AVS in lateralization of PA when the results of AVS are not conclusive. To be a substitute for AVS, however, it should fulfill various conditions including high selectivity and binding affinity to CYP11B2, high sensitivity in detecting small adenoma, high resolution image, reduction of radiation exposure, and general versatility. Considering the potential number of patients, cost-effectiveness of the subtype testing in the clinical practice of PA could be one of the issues of the medical expenses. Thus, development of a new non-invasive functional imaging will have a significant impact on the clinical practice of PA and hypertension.

The utility of the corticotropin test to diagnose adrenal insufficiency in critical illness: an update.

OBJECTIVE: One of the most common dynamic testing procedures for assessment of adrenocortical function is the standard corticotropin or the cosyntropin test. The aim of this review was to examine the evidence base underlying the corticotropin test in the management of the critically ill patient. DATA SYNTHESIS: The principle behind the corticotropin test is the demonstration of an inappropriately low cortisol production in response to exogenous ACTH, a situation analogous to physiological stress. The corticotropin test was originally described in nonstressed subjects, and its applicability and interpretation in the setting of critical illness continues to generate controversy. Attempting to determine the prevalence of an abnormal corticotropin test in critical illness is complicated by the use of different end-points and different populations. Moreover, the test result is also influenced by the assay used for measurement of plasma cortisol. Trials assessing the relationship between corticotropin response and severity of stress and organ dysfunction have produced divergent results, which may reflect differences in the methodology and the association being measured. Moreover, controversy exists with respect to the methodology and the interpretation with respect to the following variables: dose of corticotropin, end-points for assessment of total or free cortisol, effect of plasma cortisol variability, adrenal blood flow and its equivalence with other tests of adrenocortical function. CONCLUSIONS: The corticotropin test is used widely in the evaluation of adrenocortical function in the endocrine clinics. Its role in the critically ill patient is less well established. Several confounding variables exist and to have a 'one-size-fits-all' approach with a single end-point in the face of several methodological and pathophysiological confounders may be flawed and may result in the institution of inappropriate therapy. The current evidence does not support the use of the corticotrophin test in critical illness to assess adrenocortical function and guiding steroid therapy in critical illness.

Evaluation of the hypothalamic-pituitary-adrenal axis function in childhood and adolescence.

The hypothalamic-pituitary-adrenal (HPA) axis plays an important role in the maintenance of basal and stress-related homeostasis. The hypothalamus controls the secretion of adrenocorticotropic hormone (ACTH) from the anterior pituitary, which in turn stimulates the secretion of glucocorticoids from the adrenal cortex. Glucocorticoids, the final effectors of the HPA axis, regulate a broad spectrum of physiologic functions essential for life and exert their effects through their ubiquitously distributed intracellular receptors. Alterations in the activity of the HPA axis may present with symptoms and signs of glucocorticoid deficiency or excess. Detailed endocrinologic evaluation is of primary importance in determining the diagnosis and/or etiology of the underlying condition. We review the most common endocrinologic investigations used in the evaluation of the HPA axis integrity and function.