Harvinder Chahal

Imperial College Healthcare NHS Trust · Division of Diabetes and Endocrinology

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...

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...

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...

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...

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...

Introduction: Glucagon-like peptide 1 (GLP1) agonists are highly effective agents for the treatment of obesity and type 2 diabetes (T2D). GLP-1 is also implicated in outcomes of bariatric surgery, including appetite changes and T2D remission. Rare, potentially deleterious mutations in the glucagon-like peptide 1 receptor gene (GLP1R) may, therefore...

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...

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...

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...

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...

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...

"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...

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...

Some patients suffer disabling hypoglycaemia after RYGB, typically post prandially: Post Bariatric Hypoglycaemia (PBH). We hypothesised that these patients have increased glycaemic variability (GV), as assessed by continuous glucose monitoring (CGM). Method: Prospective study of 6 patients undergoing RYGB with mixed meal tests (MMT) and CGM at base...

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...

Introduction: An excessively long blind-end of the alimentary limb following RYGB, known as a ‘candy cane’ (CC), may cause symptoms such as pain, gastrointestinal symptoms and weight regain. Very few studies have examined the efficacy of surgical resection of the CC. We aimed to assess symptom resolution following CC surgery. Methods: Single centr...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...