Gastrin releasing peptide and gastrin releasing peptide receptor expression in gastrointestinal carcinoid tumours.

AIMS: To establish whether gastrin releasing peptide (GRP) and the GRP receptor (GRPR) are expressed together in gastrointestinal carcinoid tumours. METHODS: Twenty six carcinoid tumours from the stomach, small intestine, appendix, and colorectum were investigated by immunohistochemistry for GRP and GRPR. RESULTS: GRP was detected in nine of 19 tumours and GRPR in 22 of 26. Coexpression of both the ligand and receptor was seen in six of 19 cases. GRPR but not GRP was more strongly expressed in appendix and colonic tumours. CONCLUSIONS: GRP and GRPR are produced by a large number of gastrointestinal carcinoid tumours. An autocrine/paracrine pathway may exist for GRP stimulated cell proliferation in some of these neoplasms, analogous to that seen in small cell anaplastic carcinoma of the lung.

Hypokalaemia during insulin-induced hypoglycaemia in hypopituitary adults with and without growth hormone deficiency.

OBJECTIVE: We have investigated plasma potassium changes during insulin-induced hypoglycaemia (IIH) in adult patients with growth hormone deficiency (GHD) who have low total body potassium and may also have a vulnerable myocardium due to an increased prevalence of atherosclerosis. DESIGN: Hypoglycaemia was induced through the administration of intravenous soluble insulin (0.1 U/Kg, i.v.). SUBJECTS: 23 consecutive adult patients undergoing routine biochemical evaluation for hypopituitarism. MEASUREMENTS: GH, cortisol glucose, sodium and potassium levels were measured at 0, 30, 60, 90 and 120 min after insulin administration. Pituitary function was also assessed through measurement of TSH, thyroid hormones, LH/FSH, testosterone and 17-oestradiol. IGF-I concentrations were also analysed. RESULTS: All patients achieved adequate hypoglycaemia (nadir glucose < 2 mmol/l). 15 patients had GHD (peak GH < 10 mU/l) either in isolation or as part of a spectrum of pituitary hormone deficiencies. The remaining 8 patients had normal pituitary function. Plasma potassium concentrations (mean +/- SEM) fell from 3.8 +/- 0.3 mmol/l (normals) and 3.8 +/- 0.2 mmol/l (GHDs) to nadir concentrations of 3.0 +/- 0.2 mmol/l and 3.1 +/- 0.3 mmol/l, respectively (P < 0.005). Overt hypokalaemia (< 3.5 mmol/l) occurred in 13/15 GHDs and all normals. There were no significant differences between the groups. CONCLUSIONS: Insulin-induced hypoglycaemia causes similar degrees of significant hypokalaemia in patients with normal pituitary function and in those with GH deficiency, either alone or in combination with other pituitary hormone deficiencies. Therefore, insulin-induced hypoglycaemia does not appear to be associated with any greater risk of hypokalaemia in hypopituitary adults with GHD compared to those with normal anterior pituitary function.

A comparison between short ACTH and insulin stress tests for assessing hypothalamo-pituitary-adrenal function.

OBJECTIVE: Insulin-induced hypoglycaemia is the standard method for assessment of the hypothalamo-pituitary-adrenal (HPA) axis of patients with pituitary or hypothalamic disease. It has been claimed that a normal cortisol response to the 30-minute ACTH stimulation test (AST) obviates the need to perform the insulin stress test (IST) in these patients. The objective of our study was to compare both tests in a group of consecutive patients with pituitary disease. SUBJECTS AND METHODS: Thirty patients with pituitary disease were evaluated by standard IST (0.1 U of soluble insulin/kg body weight, i.v.) after fasting from midnight and AST (250 micrograms synacthen, i.v.). In the IST, a plasma glucose of < 2.2 mmol/l was taken as the hypoglycaemic threshold and blood was collected at 0, 30, 60, 90 and 120 minutes. In the AST blood was collected at 0 and 30 minutes. Serum cortisol was measured by standard radioimmunoassay and glucose by the glucose oxidase method. Cortisol responses to the stimuli were compared at cut-off levels of 550, 500, 450 and 400 nmol/l. RESULTS: At 550 nmol/l, out of 30 patients, 17 showed an abnormal IST of whom 9 had normal responses to AST (53%). At 500 nmol/l, 12 patients had an abnormal IST of whom 6 had normal AST (50%). At 450 nmol/l, of 9 patients with an abnormal IST, 5 had a normal AST (56%). At 400 nmol/l, 5 patients had an abnormal IST all of whom (100%) showed a normal AST. CONCLUSION: There is a clear discrepancy between the results of the two tests at different cortisol cut-off levels. The ACTH stimulation test is not reliable for assessing the HPA axis in patients with pituitary disease and the insulin stress test remains the standard method.