pheochromocytomas are adreno - medullary tumors characterized by catecholamine excess . impaired glucose tolerance and diabetes mellitus this has been attributed to multiple mechanisms including insulin resistance at the level of skeletal muscle and liver , enhanced gluconeogenesis but the major effect is inhibition of insulin release from the pancreas . there have been anecdotal case reports of hypoglycemia in patients with pheochromocytoma prior to surgical removal of the tumor . in these six cases , hypoglycemia was attributed to the predominant -adrenoreceptor stimulatory effect for the release of insulin . here a 51-year - old female initially presented to the department of surgery with complaint of recurrent nonbilious vomiting . there was a history of frequent intake of meals at an interval of 3 - 4 hrs . she was diagnosed to be hypertensive around 3 years back , but she was not taking regular medication . she had been taking tablet amlodipine 10 mg and olmesartan 40 mg and referred to the endocrine unit . examination revealed a thin built female of height 53 , weight 43 kg , bmi : 16.79 kg / m . the 24-hour urine catecholamines were elevated [ vma : 36.63 mg / g creatinine ( 1.6 - 4.2 mg / g ) , epinephrine : 81.42 pg / ml ( < 67 pg / ml ) , norepinephrine : 876.47 ng / ml ( 95 - 446 ng / ml ) , dopamine : 51.61 pg / ml ] . postprandial glucose levels were reported as 30 mg / dl and 54 mg / dl on two different occasions . an extended oral glucose tolerance test was done which showed reactive hypoglycemia and hyperinsulinemia at 3 hrs [ table 1 ] . ct abdomen and pelvis showed partially necrotic , otherwise well defined mass in the right adrenal measuring 42  39 mm in size . echocardiography revealed severe concentric left ventricular hypertrophy , mild mr , ar and lv diastolic dysfunction with left ventricular ejection fraction of 60% . extended oral gtt with 75 g of glucose patient underwent surgery after appropriate hypertensive management with  and -blockers . histopathology revealed tumor cells with abundant amphophilic granular cytoplasm , vesicular nuclei and few cells showed nucleoli with occasional mitotic figures suggestive of pheochromocytoma [ figure 1 ] . glucose tolerance and diabetes mellitus has been reported to be in as many as 26 - 50% patients in a semilogical study of 2585 patients , including 11 with pheochromocytoma . isotani et al . reported a young patient with na predominant pheochromocytoma presenting with dka . another case of dka in a 29-year - old patient was reported by edelman in the year 1992 which was attributed to catecholamine excess . stimulation of -adrenoreceptors by catecholamines causes enhanced glycogenolysis and gluconeogenesis by the liver resulting in transient increase in glucose production . direct stimulation by noradrenaline on -adrenoreceptors of pancreas , causes inhibition of insulin release whereas stimulation of -adrenoreceptors by adrenaline , results in insulin release , specially in conditions where glycogen stores are depleted . in most situations the -receptor - mediated insulin inhibition predominates over -insulin - releasing actions causing impairment of glucose homeostasis . hypoglycemia in these cases is believed to be due to sudden loss of catecholamine effect on glucose homeostasis . there are only anecdotal case reports of hypoglycemia in patients of pheochromocytoma in the preoperative phase . till date reactive or postprandial hypoglycemia , occurs exclusively after meals , typically within 4 hours after food ingestion . the biochemical criteria for defining postprandial hypoglycemia are a plasma glucose concentration less than 3.0 mmol / l ( 54 mg / dl ) and an insulin concentration greater than 18 pmol / l ( 3.0 pmol / l ) . previous cases of hypoglycemia reported in patients with pheochromocytoma the first case of hypoglycemia in a normotensive pheochromocytoma was reported by hagiwara in the year 1981 . innerman and his colleagues in 1982 reported a patient of pheochromocytoma that had metastasized to the liver . the author proposed that hypoglycemia was due to secretion of insulin or a substance with insulin - like activity by the tumor , increased utilization of glucose by the malignant cells and a local effect of the tumor on the hepatic parenchyma . reported a case of pheochromocytoma of paroxysmal type with paradoxical response to glucose tolerance test . in 1987 , kazuko hiramatsu reported a case of pheochromocytoma with dilated cardiomyopathy , in whom transient hyperinsulinemia and reactive hypoglycemia were reported on one occasion during extended gtt , which could not be reproduced on subsequent glucose load . ( 2008 ) reported a case of pheochromocytoma crisis presenting with profound hypoglycemia and subsequent hypertension . the author postulated that in conditions of depleted stores of glycogen in liver and skeletal muscles , stimulation of -adrenoreceptors by adrenaline , causes increase release of insulin thereby causing hypoglycemia . he postulated that hypoglycemia in this patient was because of increased consumption of glucose by the rapidly dividing tumor cells . our patient had impaired fasting glucose with glucose levels rising to more than 250 mg / dl at 1 hr . hyperinsulinemia was observed at 1 and 2 hrs . while the patient had frequent food intake and occasional headaches , classical symptoms of hypoglycemia an incidental finding of mural thickness at gastric outlet can not explain postprandial hypoglycemia in our patient , rather delayed absorption and delayed increase in plasma glucose levels would be expected . since the patient has presented with vomiting , it is possible that the glycogen stores in muscle and liver were depleted further contributing to hypoglycemia . another interesting thing in our patient is that she is never been symptomatic for hypoglycemic symptoms even when the plasma glucose levels were 30 mg / dl .
pheochromocytoma , a tumor characterized by catecholamine excess , is usually associated with impaired glucose tolerance . 
 hypoglycemia may occur after the abrupt withdrawal of catecholamines in the postoperative period . 
 rarely , insulin secretion by stimulation of -2 adrenoreceptors may overwhelm the glucagon production , thereby causing hypoglycemia . here , we describe a female with pheochromocytoma , who presented with postprandial hypoglycemia .