Harvinder Chahal

Harvinder Chahal
Imperial College Healthcare NHS Trust · Division of Diabetes and Endocrinology

BMedSci, MBBS, MRCP, PhD

About

65
Publications
6,705
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1,522
Citations
Additional affiliations
December 2012 - present
Imperial College Healthcare NHS Trust
Position
  • Consultant Endocrinologist and Lead Bariatric Physician

Publications

Publications (65)
Article
Bariatric surgery for obesity remains the most effective method to achieve weight loss and improvements in mortality. However, as the number of procedures increases to match the rising burden of obesity, unusual metabolic complications are now coming to the fore. One example of this is postprandial hypoglycaemia (PPH). The incidence of PPH has been...
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Full-text available
Gigantism results when a growth hormone-secreting pituitary adenoma is present before epiphyseal fusion. In 1909, when Harvey Cushing examined the skeleton of an Irish patient who lived from 1761 to 1783, he noted an enlarged pituitary fossa. We extracted DNA from the patient's teeth and identified a germline mutation in the aryl hydrocarbon-intera...
Article
Familial pituitary adenomas can occur in MEN1 and Carney complex, as well as in the recently characterized familial isolated pituitary adenoma (FIPA) syndrome. FIPA is an autosomal dominant disease with incomplete penetrance, characterized by early-onset disease, often aggressive tumor growth and a predominance of somatotroph and lactotroph adenoma...
Article
Complex changes occur within the endocrine system of ageing individuals. This article explores the changes that occur in the metabolism and production of various hormones and discusses the resulting clinical consequences. As individuals age there is a decline in the peripheral levels of oestrogen and testosterone, with an increase in luteinizing ho...
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Obesity is associated with multiple comorbidities and psychosocial burdens, but often sexual dysfunction (SD) is overlooked. Bariatric surgery is the most effective treatment for morbid obesity, and its role in reversing SD is reviewed. A literature search of MEDLINE, PubMed Central, and Cochrane databases was conducted. Fifty-six articles were ide...
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Objective: The aim of this study was to examine the clinical efficacy and safety of the duodenal-jejunal bypass liner (DJBL) while in situ for 12 months and for 12 months after explantation. Summary Background Data: This is the largest randomized controlled trial (RCT) of the DJBL, a medical device used for the treatment of people with type 2 diab...
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Background Roux-en-Y gastric bypass is recognised as a standard of care in the treatment of diabetes mellitus and obesity. However, the optimal length of the Roux-en-Y gastric bypass limbs remains controversial, with substantial variation in practice. Specifically, a longer biliopancreatic limb length of 150 cm (‘long limb’) has been hypothesised t...
Article
Background : The COVID-19 pandemic has created unprecedented pressures on healthcare systems worldwide, necessitating a reorganisation of elective services. Within all specialties, including bariatric surgery, this required a re-evaluation of patient prioritisation to limit harm due to delays in treatment while ensuring those who will benefit most...
Article
Objective: Roux-en-Y gastric bypass (RYGB) is an established treatment for type 2 diabetes and obesity. The study objective was to establish RYGB's effects on glycemic variability (GV) and hypoglycemia. Research design and methods: This was a prospective observational study of 10 participants with obesity and prediabetes or type 2 diabetes who u...
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Objective: Roux-en-Y gastric bypass (RYGB) characteristically enhances postprandial levels of glucagon-like peptide 1 (GLP-1), a mechanism that contributes to its profound glucose-lowering effects. This enhancement is thought to be triggered by bypass of food to the distal small intestine with higher densities of neuroendocrine L-cells. We hypothe...
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"Imperial Satiety Protocol" (I-SatPro) is a new multi-faceted approach to weight-loss for people with obesity (PwO), encompassing dietary advice, time restricted eating, physical activity, and coaching to support behaviour change. Participants (n = 84) attended fortnightly I-SatPro group sessions for 30 weeks, with 70% of participants completing. O...
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Background An excessively long-blind end of the alimentary limb following a Roux-en-Y gastric bypass (RYGB), known as a ‘candy cane’ (CC), may cause symptoms including abdominal pain, regurgitation and vomiting. Very few studies have examined the efficacy of surgical resection of the CC. Objectives The aim of this study was to assess sensitivity o...
Article
Background: Many patients with type 2 diabetes do not achieve sustained diabetes remission after metabolic (bariatric) surgery for the treatment of obesity. Liraglutide, a glucagon-like peptide-1 analogue, improves glycaemic control and reduces bodyweight in patients with type 2 diabetes. Our aim was to assess the safety and efficacy of liraglutid...
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Full-text available
Objective Roux-en-Y gastric bypass (RYGB) surgery is currently the most effective treatment for diabetes and obesity. An increasingly recognized and highly disabling complication of RYGB is postprandial hypoglycaemia (PPH). The pathophysiology of PPH remains unclear with multiple mechanisms suggested including nesidioblastosis, altered insulin clea...
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Purpose: This study aimed to determine the predictive power of the DiaRem score following Roux-en-Y gastric bypass to identify patients who would have diabetes remission at 1 year in an ethnically diverse population. Methods: We performed a retrospective review of 262 patients with type 2 diabetes mellitus who underwent RYGB at the Imperial Weig...
Article
Obesity is an important modifiable risk factor for musculoskeletal disease. A Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)-compliant systematic review of bariatric surgery on musculoskeletal disease symptoms was performed. One thousand nineteen papers were identified, of which 43 were eligible for data synthesis. Ther...
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We present the case of a patient with metastatic parathyroid carcinoma whose hypercalcaemia was medically managed through two pregnancies. The diagnosis was made when the patient presented with chronic knee pain and radiological findings consistent with a brown tumour, at the age of 30. Her corrected calcium and parathyroid hormone (PTH) levels wer...
Article
Context: Germline AIP mutations usually cause young-onset acromegaly with low penetrance in a subset of familial isolated pituitary adenoma families. We describe our experience with a large family with R304* AIP mutation and discuss some of the diagnostic dilemmas and management issues. Objective: The aim of the study was to identify and screen...
Article
Abnormal microRNA (miRNA) expression profiles have recently been associated with sporadic pituitary adenomas, suggesting that miRNAs can contribute to tumor formation; miRNAs are small noncoding RNAs that inhibit posttranscriptional expression of target mRNAs by binding to target sequences usually located in the 3'-UTR. In this study, we investigat...
Article
The model of "oncogene-induced senescence" (OIS), resulting in cell-proliferation arrest, has recently been suggested as a possible explanation for the non-progression of pituitary tumours to malignancy. The aim of the study was to compare the expression of β-galactosidase as a molecular marker of OIS, and p21/p16 as additional markers involved in...
Article
Somatotroph adenomas harboring aryl hydrocarbon receptor interacting protein (AIP) mutations respond less well to somatostatin analogs, suggesting that the effects of somatostatin analogs may be mediated by AIP. The objective of the investigation was to study the involvement of AIP in the mechanism of effect of somatostatin analogs. In the human st...
Article
Pituitary adenomas usually occur as sporadic tumors, but familial cases are now increasingly identified. As opposed to multiple endocrine neoplasia type 1 and Carney complex, in familial isolated pituitary adenoma (FIPA) syndrome no other disease is associated with the familial occurrence of pituitary adenomas. It is an autosomal dominant disease w...
Article
Full-text available
Familial isolated pituitary adenoma (FIPA) is an autosomal dominant condition with variable genetic background and incomplete penetrance. Germline mutations of the aryl hydrocarbon receptor interacting protein (AIP) gene have been reported in 15-40% of FIPA patients. Limited data are available on the functional consequences of the mutations or rega...
Article
Ependymomas rarely arise from the region of the pituitary fossa, with only four cases previously reported in the literature. We present a complex case of a recurrent ependymoma of the parasellar region which has been difficult to clinically manage due to its tendency to recurrence. Our patient has had four operations over the last 28 years, with ex...
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Germline mutations in the MEN1 gene predispose to the multiple endocrine neoplasia (MEN1) syndrome; however, approximately 10-20% of patients with MEN1 do not have a detectable MEN1 mutation. A rat strain with multiple endocrine tumours, a phenotypic overlap of both MEN1 and MEN2, has been reported to have a homozygous germline p27 (CDKN1B) mutatio...
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Full-text available
Mutations have been identified in the aryl hydrocarbon receptor-interacting protein (AIP) gene in familial isolated pituitary adenomas (FIPA). It is not clear, however, how this molecular chaperone is involved in tumorigenesis. AIP sequence changes and expression were studied in FIPA and sporadic adenomas. The function of normal and mutated AIP mol...
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Full-text available
The epidemic of type 2 diabetes worldwide continues unabated. Despite a number of existing therapies, treatment goals are seldom fully achieved. While insulin resistance and beta cell failure remain important in the pathogenesis of the condition, the role of incretin hormones in glucose homeostasis has recently become clearer. Incretins have severa...
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Full-text available
The cyclin-dependent kinase inhibitor p27(Kip1) (p27) plays a pivotal role in controlling cell proliferation during development and tumorigenesis. p27 has been implicated in pituitary tumorigenesis in studies of knockout mice and in analyses of human pituitary tumor samples. In this study, we further explored the role of p27 in human pituitary tumo...

Projects

Projects (2)
Project
Hypotheses The main anatomical difference between long-limb RYGB and standard-limb RYGB is that the segment of the bypassed proximal intestine, the biliopancreatic limb, is longer (150 vs. 50cm respectively). This means that in the long-limb RYGB the common channel is shorter, and as a result nutrients reach the distal small bowel faster and in a less-digested state. The physiological mechanisms through which these changes in anatomy can alter glucose homeostasis are not currently known. We hypothesize that the long-limb RYGB is better for T2DM because: 1. It increases the immediate post-prandial insulin secretion significantly more than the standard-limb RYGB, by enhancing the post-prandial secretion of gut hormones, and in particular glucagon-like peptide (GLP) -1, over that seen with the standard-limb RYGB. 2. It increases insulin sensitivity significantly more than the standard-limb RYGB, before and after weight loss has taken place. Objectives Our objectives are to compare the standard and the long-limb RYGB in terms of the differences in: 1. Insulin and gut hormone secretion, following a standardised mixed meal tolerance test. 2. Insulin sensitivity (hepatic and peripheral), using the two-step euglycaemic-hyperinsulinaemic clamp method. 3. Changes in plasma bile acid levels. 4. Gut bacterial diversity and their metabolite profile. Trial team The Chief Investigator is Professor Stephen R. Bloom, Professor of Medicine and Head of Department of Investigative Medicine, Imperial College London. Co-investigators and collaborators are Prof Francesco Rubino (King’s College London), Dr Alexander Miras, Dr Belén Pérez Pevida, Miss Anna Kamocka, Mr Ahmed Ahmed, Dr Tricia Tan, Prof Gary Frost, Prof Jeremy Nicholson, Prof Elaine Holmes, Prof Margot Umpleby (University of Surrey), Prof Ameet Patel (Kings College London), Mr Sanjay Purkayastha, Mr Krishna Moorthy, Miss Avril Chang (King’s College London), Dr Harvinder Chahal and Dr Julian Marchesi. Trial design It is a prospective double-blinded randomised controlled clinical trial. Fifty patients will be recruited from the Imperial Weight Centre and the King’s College Obesity Clinic, and randomised to either the long-limb or the standard-limb RYGB surgery. ISRCTN15283219 DOI 10.1186/ISRCTN15283219
Project
This study is designed to investigate the clinical effects and mechanisms of action of pharmacological administration of the GLP-1 analogue liraglutide on glycaemic control in patients whose T2DM is suboptimally controlled after RYGB or VSG bariatric surgery. Trial team: The Chief Investigator is Professor Stephen R. Bloom, Professor of Medicine and Head of Department of Investigative Medicine, Imperial College London. PI: Prof Tricia Tan. Co-investigators Dr. Belén Pérez Pevida, Dr Alexander Miras, Dr Samantha Scholtz, Ms Rachel Gibson, Miss Anna Kamocka, Dr Harvinder Chahal, Miss Candace Bovill-Taylor, Ms Athena Foran, Emma Rose McGlone, Mrs Madawi Aldhwayan and Miss Georgina Hayman (lay member). Trial design This is a prospective randomized double-blind placebo-controlled clinical trial. Eighty patients who have undergone RYGB or VSG surgery at least 12 months before randomization and have suboptimally controlled T2DM with a glycated haemoglobin (HbA1c) of >6.5% (>48 mmol/mol) will be recruited from the Imperial Weight Centre, an International Centre of Excellence for bariatric surgery, or other approved. Additional patients will be identified from patient identification centres. Patients will be randomised to either treatment with the GLP-1 receptor agonist liraglutide (Victoza®, Novo Nordisk, Crawley, UK; n=54) or liraglutide placebo (saline; n=26) and treated for 6 months. The computer-generated randomisation sequence will be stratified by type of surgery. EudraCT Number: 2014-003923-23 Sponsor's Protocol Code Number: 1.1 National Competent Authority: UK - MHRA Clinical Trial Type: EEA CTA Trial Status: Ongoing Date on which this record was first entered in the EudraCT database: 2015-08-25 Link: https://www.clinicaltrialsregister.eu/ctr-search/trial/2014-003923-23/GB/