Ritonavir and cobicistat, used as pharmacokinetic enhancers in combination with some antiretrovirals (ARVs) for the treatment of HIV, are potent inhibitors of the CYP3A4 isoenzyme. Most glucocorticoids are metabolised via the CYP3A4 pathway and iatrogenic Cushing's syndrome (ICS), with possible secondary adrenal insufficiency (SAI), is a recognised complication following co-administration with ritonavir or cobicistat. A structured approach for identifying and managing potentially affected individuals has not been established. We systematically identified patients with ICS/SAI and found substantial heterogeneity in clinical practice across three large London HIV centres. While this significant drug interaction and its complications are now well-recognised, it is apparent that there is no standardised approach to management or guidance for the general physician. Here we describe the management of ICS/SAI in our current practice, review the available evidence and suggest practice recommendations. KEYWORDS : Adrenal insuffi ciency , cobicistat , Cushing's syndrome , HIV , ritonavir IntroductionRitonavir and cobicistat are pharmacokinetic enhancers used in the treatment of HIV infection. They are extremely potent inhibitors of cytochrome P450 3A4 (CYP3A4) activity. Ritonavir, originally developed as an antiretroviral, is used ABSTRACT Iatrogenic Cushing's syndrome due to drug interaction between glucocorticoids and the ritonavir or cobicistat containing HIV therapies at sub-therapeutic doses, in combination with HIV protease inhibitors (PIs), to significantly increase their concentrations and allow less frequent and lower dosing.1 Cobicistat was developed more recently and is similar in structure. It is used in combination with PIs or elvitegravir (an integrase inhibitor) 2 but has no antiretroviral activity itself. 3 The downside of this pharmacokinetic manipulation is the significant potential for interactions with CYP3A4 substrates, leading to side effects. CYP3A4 is the dominant isoenzyme of the hepatic cytochrome P450 system and is the primary metabolic step for the degradation of endogenous and most prescribed corticosteroids. The metabolism of these can therefore be decreased by inhibitors such as ritonavir/cobicistat. 4 Subsequent increases in exogenous corticosteroid plasma concentrations and half-life can lead to iatrogenic Cushing's syndrome (ICS) 5 and, at supraphysiological levels, to suppression of adrenocorticotropic hormone (ACTH) and endogenous corticosteroid secretion, potentially resulting in secondary adrenal insufficiency (SAI). There is abundant evidence highlighting this issue. 1,[6][7][8][9][10][11] However, a structured approach to identify and manage potentially affected individuals has not been established. We aim to summarise the current management of ICS/SAI in three large HIV patient cohorts, review the available literature and develop practice recommendations. Of note, cobicistat became available after the evaluation period covered; however, all advice for ritonavir is applicable to i...

Amiodarone is an anti-arrhythmic drug that commonly affects the thyroid, causing hypothyroidism or thyrotoxicosis. Amiodarone-induced thyrotoxicosis (AIT) is caused by excessive thyroid hormone biosynthesis in response to iodine load in autonomously functioning thyroid glands with pre-existing nodular goitre or underlying Graves' disease (type 1 or AIT 1), or by a destructive thyroiditis typically occurring in normal glands (type 2 or AIT 2). Indeterminate or mixed forms are also recognized. The distinction is clinically useful as AIT 1 is treated predominantly with thionamides, whereas AIT 2 is managed with glucocorticoids. We review the tools used to differentiate type 1 from type 2 thyrotoxicosis, with specific reference to the imaging modalities used.

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SummaryVitamin D is widely reported to inhibit innate immune signalling and dendritic cell (DC) maturation as a potential immunoregulatory mechanism. It is not known whether vitamin D has global or gene-specific effects on transcriptional responses downstream of innate immune stimulation, or whether vitamin D inhibition of innate immune signalling is common to different cells. We confirmed vitamin D inhibition of nuclear factor-jB (NF-jB) and p38 mitogen-activated protein kinase (MAPK) signalling in monocyte-derived DC (MDDC) stimulated with lipopolysaccharide (LPS). This was associated with global but modest attenuation of LPS-induced transcriptional changes at genome-wide level. Surprisingly, vitamin D did not inhibit innate immune NF-jB activation in monocytederived macrophages. Consistent with our findings in MDDC, ex vivo vitamin D treatment of primary peripheral blood myeloid DC also led to significant inhibition of LPS-inducible NF-jB activation. Unexpectedly, in the same samples, vitamin D enhanced activation of both NF-jB and MAPK signalling in primary peripheral blood monocytes. In a cross-sectional clinical cohort, we found no relationship between peripheral blood vitamin D levels and LPS-inducible activation of NF-jB and MAPK pathways in monocytes of myeloid DC. Remarkably, however, in vivo supplementation of people with vitamin D deficiency in this clinical cohort also enhanced LPS-inducible MAPK signalling in peripheral blood monocytes. Therefore, we report that vitamin D differentially modulates the molecular response to innate immune stimulation in monocytes, macrophages and dendritic cells. These results are of importance in the design of studies on vitamin D supplementation in infectious and immunological diseases.

The assay studied specifically identifies patients with Graves' disease. It is a reliable tool in the initial clinical assessment to determine the aetiology of hyperthyroidism and has the potential for cost-savings.