ACTH and beta-endorphin secretion by three corticotrophic adenomas in culture. Effects of culture time, dexamethasone, vasopressin and synthetic corticotrophin releasing factor

Medical management of pituitary adenomas: structural and ultrastructural changes

The morphology of the various pituitary cell types is highly dynamic and allows recognition of many cellular functions. Most pituitary cells show morphologic changes that reflect stimulation or inhibition by hormones. Drugs have also been shown to alter the morphology of several pituitary tumor types, allowing a measure of therapeutic efficiency and a careful dissection of the mechanisms of action of various medical therapies. In some cases, these morphologic alterations can evoke diagnostic problems.

Higher incidence of severe hypoglycaemia leading to hospital admission in Type 2 diabetic patients treated with long-acting versus short-acting sulphonylureas

AIMS

A comparison of the frequency of severe hypoglycaemia leading to hospital admission in people with Type 2 diabetes mellitus (DM) treated with long vs. short-acting sulphonylureas.

METHODS

A community based study over a 12-year period in the population of the city of Basle, Switzerland. The number of diabetic patients treated with oral hypoglycaemic agents was established on the basis of tablet consumption and a defined daily dose, e.g. 7.5 mg for glibenclamide, and 50 mg for glibornuride.

RESULTS

Twenty-eight Type 2 diabetic patients were admitted for severe hypoglycaemia, with a median age of 73 years. There were no deaths. Sixteen of these admissions were patients treated with long-acting sulphonylureas and 12 were patients treated with short-acting forms. Only 23.5% of the population with Type 2 DM in Basle were treated with long-acting sulphonylureas. With 30345 person-years of observation, the incidence of severe hypoglycaemia was 2.24 per 1000 person-years for long-acting sulphonylureas vs. 0.75 per 1000 person-year for short-acting forms, odds ratio 3.01 (95% confidence interval 1.35-6.77). Decreased food intake (nine patients) was a major contributing factor.

CONCLUSIONS

Severe hypoglycaemia leading to hospital admission is more common in elderly Type 2 diabetic patients treated with long-acting compared to short-acting sulphonylureas. Such long-acting sulphonylureas should be avoided.

The combined use of size-exclusion and reversed-phase high-performance liquid chromatography for characterization of beta-endorphin processing pathways

A method is described for the separation and analysis of multiple molecular forms of immunoreactive beta-endorphin and its alpha-N-acetylated congeners by a combination of reversed-phase and size-exclusion high-performance liquid chromatography coupled with two specific radioimmunoassays. Both chromatographic procedures are fast (less than 50 min per analysis) providing good resolution and high recovery (greater than 90%). The solvents used in both systems are ultraviolet transparent (less than 214 nm), non-corrosive, low salt (less than 0.05 M) and after evaporation fully compatible with subsequent radioimmunoassay. We have evaluated these techniques using both synthetic and purified peptide standards and have applied these procedures to characterize immunoreactive beta-endorphin and alpha-N-acetylendorphin in rat and sheep pituitary extracts, and the low levels found in sheep hypothalamus and rat ovary. These chromatographic procedures are not only applicable to the study of pro-opiomelanocortin-derived peptides, but also could be employed to examine the processing pathways of other biologically active polypeptides, in both central and peripheral tissue extracts.

The CRFs and their control: chemistry, physiology and clinical implications

The 41-amino acid CRF fulfils all the criteria for a corticotrophin releasing factor, although considerable evidence suggests that other factors, particularly VP, also play a physiologically significant role in controlling ACTH release. Although human CRF has now been identified as a 41-residue peptide, most studies to date have used oCRF-41 in their exploration of the physiology and pathology of the hypothalamic--pituitary--adrenal axis. Low doses of oCRF-41 appear to be safe, and for specific tests of the readily-releasable pool of ACTH and related peptides 100 micrograms is a practical dose for most purposes. Although serious side-effects have only been noted at doses above 100 micrograms, it is reasonable to monitor all patients administered CRF-41 with great care, and in particular to be alert to hypotension, especially in patients with corticosteroid deficiency. There is little doubt that, in combination with the standard insulin-tolerance test, the CRF test is a useful means of diagnosing hypothalamic or portal dysfunction in patients with secondary adrenal failure. However, in the diagnosis and differential diagnosis of Cushing's syndrome, the role of the CRF test remains unclear. In normal subjects, a high basal cortisol level usually inhibits the response to CRF, such that a greatly enhanced response is suggestive of pituitary-dependent Cushing's syndrome. In patients with diagnosed ACTH-dependent Cushing's syndrome, an absent response to CRF predisposes towards an ectopic source of ACTH. However, there are exceptions in all directions, and it is uncertain whether the CRF test will prove of greater value than the traditional procedures, such as the dexamethasone suppression test. The differential diagnosis of depression and Cushing's disease may be its greatest value. In terms of treatment, there are as yet few data on the usefulness of CRF in expediting recovery of the pituitary-adrenal axis following long-term suppression, such as in patients with Cushing's syndrome treated by removal of a unilateral adenoma or trans-sphenoidal microadenomectomy. It is possible that such treatment may eventually be a useful application of CRF, although data are not yet available.