Insulinoma: a review of current management

Is hyperinsulinemia a possible clinical explanation underlying the myth of Erysichthon?

BACKGROUND

An insulinoma is an endocrine tumor of the pancreas, originating from the beta cells, and has a prevalence of 4 cases per 1 million patients. Insulinomas often follow a "90% rule": 90% are benign [1, 2], 90% originate in the pancreas, 90% are approximately 2 cm wide, and 90% are isolated. Individuals with an insulinoma may have episodic bouts of hyperinsulinemic hypoglycemia. Typically, an insulinoma is indicated by hypoglycemic symptoms which are a result of catecholamine reaction and neuroglycopenia. There is increased secretion of insulin in patients with an insulinoma despite having lower glucose levels.

PURPOSE

This paper examines the myth of Erysichthon and speculates whether the symptoms experienced by him are possibly related to those found in patients with an hyperinsulinoma.

METHODS

The myth of Erysichthon was taken from various sources (i.e. Hesiod, Callimachus, Ovid) and examined. Symptoms of Erysichthon were then examined.

RESULTS

The myth of Erysichthon depicts various sympathoadrenal and neuroglycopenic symptoms including anxiety and abnormal behaviour which can be found in insulinomas. Insulinomas may often present a diagnostic challenge due to their deceptive nature and overlapping symptoms with other disorders such as neurologic disease. Insulinomas inducing weight loss resemble Calamachus's account of Erysichthon whose body is finally emaciated, even though having polyphagia.

CONCLUSION

The myth of Erysichthon provides an interesting range of clinical symptoms which I have argued relate to symptoms found in patients with an insulinoma. Although, insulinomas were unknown in ancient medical lore, this paper has speculated that based on Erysichthon's symptoms, the possibility of an insulinoma cannot be ruled out.

Insulinoma presenting as medically intractable temporal lobe epilepsy

We describe a female insulinoma patient who presented with recurrent attacks of abnormal behavior, confusion, and seizure. Her interictal EEG showed epileptiform discharges on the left temporal area, therefore she was initially misdiagnosed as temporal lobe epilepsy. In the video-EEG monitoring, hypoglycemic state was detected during the seizure attack, so the right diagnosis was made after the endocrinologic investigations. After surgical removal of the tumor, the patient became seizure-free, and no abnormality was found in the follow-up EEG after six months. Since insulinoma shares some common clinical and EEG features with complex partial seizure of temporal lobe origin, insulioma should be included in the differential diagnosis for medically intractable temporal lobe epilepsy.

Insulinoma with early-morning abnormal behavior

We report a 65-year-old man with insulinoma who initially developed stereotypical behaviors and then progressed to more complex behaviors occurring early in the morning. He could not remember the events during the episodes. Insulinoma was diagnosed based on fasting blood glucose level of 15 mg/dl, high fasting immunoreactive insulin/blood glucose ratio (more than 0.3), and a tumor in the pancreas head by abdominal CT. Hypoglycemia caused by insulinoma should be considered as one of the mechanisms underlying abnormal nocturnal behaviors since the symptoms are very similar to those of sleep-related epilepsy, parasomnia, and night delirium.

Diagnostic difficulties in long-standing insulinoma with near-normal plasma insulin levels

Insulinoma tumors are often difficult to detect, as the symptoms largely precede occurrence of a visualized tumor. We report the case of an insulinoma patient with long delayed diagnosis and marked adaptation to extreme hypoglycemia. The patient with a 7-yr history of seizures was found to have plasma glucose concentration during a starvation test as low as 16 mg/dl, with no clinically significant symptoms and concomitant normal plasma insulin levels: 10-30 microIU/ml. All attempts to localize a tumor with repeated abdominal ultrasound examinations or computed tomography scanning were unsuccessful. The patient did not tolerate the introduced oral treatment with diazoxide. Once it had become technically available, endoscopic ultrasonography of the pancreas was performed. It revealed a 10 mm tumor in the pancreatic head. The tumor was subsequently removed surgically. During the operation plasma insulin concentration rose almost 15-fold, which confirmed the insulin-secreting character of the growth. Microscopic examination revealed benign insulinoma, with partially trabecular structure. One month after the operation the patient had normal plasma glucose values of 60-120 mg/dl, but she constantly complained of excessive thirst, which occurred soon after the operation and slowly subsided in the following weeks. In conclusion, the present report demonstrates that insulinoma should be considered and searched for in every case of hypoglycemia associated with normal insulin levels. It also confirms the essential role of endoscopic ultrasonography in the diagnosis of insulin-secreting tumors.

Insulinoma

Insulinomas are the most common islet cell tumors and are located almost exclusively in the pancreas. Most of these tumors are sporadic, but they may also be associated with the multiple endocrine neoplasia type I syndrome. More than 90% of insulinomas are benign. Preoperative radiographic localization may prove difficult. Intraoperative palpation and ultrasound remain the gold standard for detection and appropriately planned resection. Although many options are available to treat the patient with malignant and metastatic disease, the mainstay of treatment remains surgery. Laparoscopic ultrasound and enucleation/resection may be increasingly used in the management of patients with insulinoma.

Lessons to be learned: a case study approach insulinoma presenting as a change in personality

A 43-year-old man presented with attacks of altered behaviour over a short period of time; they were associated with episodes of hypoglycaemia. The clinical suspicion of insulinoma prompted investigations that quickly established serum insulin and C-peptide levels to be elevated at the times when blood glucose values were low. A physical lesion was found in the head of the pancreas by means of computerised tomography and endo-duodenal ultrasound scan; an octreotide scan was negative. The patient underwent laparotomy and enucleation of a benign tumour, measuring 2.6 cm in diameter, lying within the head of the pancreas; histological examination confirmed it to be an insulinoma. Postoperatively, the patient's personality gradually became more normal and his fasting blood glucose concentrations returned to within normal limits. The diagnosis and management of insulinoma are discussed in the context of this clinical case; there is also reference to the protean clinical manifestations that may occur in this condition- and its differential diagnosis.

A non-insulin secreting malignant insulinoma of the pancreas

We report a rare case of a non-insulin secreting malignant insulinoma of the pancreas and discuss its medical and surgical management. Surgical excision of malignant insulinoma produces good palliation and can increase survival.