Preliminary observations using endocrine markers of pituitary venous dilution during bilateral simultaneous inferior petrosal sinus catheterization in Cushing's syndrome: is combined CRF and TRH stimulation of value?

OBJECTIVE: We determined whether the measurement of hormones in pituitary blood permits correction for dilution by non-pituitary blood during bilateral simultaneous inferior petrosal sinus blood sampling in Cushing's syndrome. DESIGN: Bilateral simultaneous inferior petrosal sinus blood sampling was performed after combined hCRF and TRH stimulation. Peak ACTH concentrations were corrected for the TSH and PRL inter-sinus ratio, assuming uniform secretion of both hormones into each inferior petrosal sinus. PATIENTS: Eight patients with clinical and biochemical features of Cushing's syndrome. MEASUREMENTS: Basal and stimulated ACTH, TSH and PRL concentrations were measured after bilateral simultaneous inferior petrosal sinus blood sampling and simultaneously from a peripheral forearm vein. RESULTS: Basal central:peripheral ACTH ratio misdiagnosed four of eight patients as having non-pituitary disease. Peak uncorrected ACTH central:peripheral ratio erroneously suggested two of eight patients had non-pituitary disease. ACTH central:peripheral ratio corrected by TSH and PRL correctly predicted pituitary-dependent disease in all eight cases and provided correct lateralization data in four of five patients with a unilateral pituitary microadenoma. CONCLUSION: This study suggests that measuring other hormones in pituitary blood after TRH stimulation can offer a simple and reliable method for correcting for dilution by non-pituitary blood during bilateral simultaneous inferior petrosal sinus blood sampling in Cushing's syndrome.

A case of multiple endocrine neoplasia: hyperparathyroidism, insulinoma, GRF-oma, hypercalcitoninaemia and intractable peptic ulceration.

A 42-year-old woman with a family history of multiple endocrine neoplasia type 1 (MEN 1) presented with symptomatic hypoglycaemia and peptic ulceration. Investigation revealed an insulinoma, hyperparathyroidism, hypercalcitoninaemia with a positive pentagastrin stimulation test, acromegaly due to a GRF-oma, hyperprolactinaemia and normal serum gastrin levels. Five pancreatic tumours were removed at laparotomy and immunostaining was positive for insulin, calcitonin, somatostatin and glucagon. Post-operatively she developed elevated serum gastrin levels and gross peptic ulceration, despite H2-blockers, and died of gastro-intestinal haemorrhage suggesting that removal of the somatostatinoma may have allowed increased gastrin secretion from a gastrinoma. This case emphasizes the importance of measuring a wide variety of tumour marker peptides in MEN 1 and suggests that caution is required in interpretation of the pentagastrin stimulation test in such cases. Patients with MEN 1 and known peptic ulceration may require perioperative omeprazole treatment even if serum gastrin levels are normal.

A retrospective audit of the combined pituitary function test, using the insulin stress test, TRH and GnRH in a district laboratory.

OBJECTIVE: To assess the value of the combined insulin stress test (IST), thyrotrophin-releasing hormone (TRH) and gonadotrophin hormone-releasing hormone (GnRH) tests. DESIGN: A retrospective audit of 232 such tests performed between 1980 and 1989 inclusive. PATIENTS: One hundred and ninety-seven patients with known or suspected pituitary disease. MEASUREMENTS: IST, TRH and GnRH responses were retrieved from laboratory records. Case notes were surveyed for clinical data and additional results. RESULTS: A basal serum cortisol level of less than 100 nmol/l (or less than 200 nmol/l in patients who had recently received glucocorticoid replacement therapy) accurately predicted a subnormal response to hypoglycaemia. All patients with a basal cortisol level of greater than 400 nmol/l, except those who had recently received steroids, showed a normal cortisol response. In retrospect, by consideration of such basal values, 55% of ISTs could have been avoided if the only aim was to assess cortisol reserve. A deficient growth hormone (GH) response to hypoglycaemia was, however, common in patients with a normal cortisol response. Two-thirds of patients with GH deficiency would have been missed if an IST had been avoided on the basis either of basal cortisol levels alone, or of cortisol responses to an alternative test which did not test GH reserve. There was poor agreement between the pituitary response to TRH and GnRH and basal levels of thyroxine and gonadotrophins respectively, suggesting that these releasing hormone tests are misleading. CONCLUSIONS: The IST provides information regarding pituitary function not provided by other tests of the hypothalamic-pituitary-adrenal axis, so that the choice between the IST and alternative tests must depend on a critical assessment of what information is required. Routine TRH and GnRH testing appears to yield little information of practical clinical value.

Isoflurane in the treatment of asthma.

A 22-month-old child developed severe bronchospasm. Prolonged ventilation of the lungs with isoflurane for 102 hours was used as treatment. The metabolism and fluoride levels obtained are discussed.

Triolein breath test of fat absorption in patients with chronic liver disease.

We have compared the [14C]triolein breath test for fat malabsorption with fecal fat excretion corrected for marker pellet recovery in 23 subjects with chronic liver disease. The breath test identified 15 of the 17 subjects with abnormal fecal fat excretion (sensitivity 88%). However, four of the six subjects with normal fecal fat excretion gave abnormal breath test results (specificity 33%). While three of the four subjects with falsely abnormal breath tests had alcoholic liver disease, the explanation for the low specificity is unclear and may not be confined to patients with alcohol-related disease. We are therefore unable to recommend the breath test as a screen for steatorrhea in patients with chronic liver disease.