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Biomedical subjects

M Buchfelder

Publications and source records attributed to M Buchfelder.

At least 127 records · Page 7Linked to original sources
PubMed1993

Clinical and biochemical characteristics of acromegalic patients harboring gsp-positive and gsp-negative pituitary tumors.

A subgroup of growth hormone (GH)-secreting pituitary tumors carries somatic mutations within the gene coding for the alpha subunit of the stimulatory heterotrimeric guanosine 5'-triphosphate-binding protein, Gs alpha. These so-called gsp mutations result in constitutively activated Gs alpha and the signal transduction cascade downstream of it, with eventual markedly and continuously elevated cyclic adenosine monophosphate levels as a result of constitutive adenylyl cyclase activity. It is this elevation of intracellular cyclic adenosine monophosphate that is thought to be the cause of excessive GH secretion and somatotroph proliferation. We examined the clinical and biochemical characteristics of acromegalics harboring gsp-positive and gsp-negative pituitary tumors. Of 19 tumors studied, 8 (42%) were gsp positive. There was a slight tendency for basal GH levels in serum to be lower and to be further reduced by an oral glucose tolerance test in gsp-positive patients. However, there was no difference between the two groups in terms of clinical features, tumor size, mitotic activity (as assessed by cytosolic deoxyribonucleic acid polymerase and KI-67 staining), and in vitro GH response to GH releasing factor. We conclude that there is, in general, little difference in the clinical and biochemical characteristics between gsp-positive and gsp-negative human pituitary GH-secreting tumors.

Acromegaly↗
PubMed1993

[Medulloblastomas--the results after postoperative radiotherapy with and without adjuvant chemotherapy].

Between 1975 and 1991, 40 patients with newly diagnosed medulloblastoma were treated at the authors' institutions. After aggressive surgical resection 39/40 (98%) received craniospinal radiation therapy with a local boost to the posterior fossa and other macroscopically involved areas. A group of 29 patients was treated with adjuvant chemotherapy. The five-year actuarial survival and event-free survival were 75% and 65%, respectively. Survival was significantly better for patients treated after 1981 as compared to those treated between 1975 and 1980 (p = .02). Younger age (two to four years) was associated with a better prognosis (p = .02). The extend of resection, Chang-stage, radiation dose to posterior fossa and the use of chemotherapy did not significantly impact on survival and relapse-free survival.

Actuarial Analysis↗
PubMed1992

Transsphenoidal microsurgery for craniopharyngioma.

We report on our series of 32 craniopharyngiomas operated on by the transsphenoidal route since 1983. In 15 of 19 patients (79%) with primary transsphenoidal surgery and in 8 of 13 patients (62%) with a transsphenoidal approach following previous surgical procedures, the craniopharyngioma was totally removed. Primary transsphenoidal surgery is a safe and successful procedure for intrasellar and suprasellar infradiaphragmatic craniopharyngiomas. In secondary surgery and in the presence of tumor calcifications the indication for this approach must be considered more carefully. Postoperative posterior pituitary deficiency is a frequent occurrence. Anterior pituitary function usually remains unchanged after surgery except for normalization of hyperprolactinemia.

Adolescent↗
PubMed1992

Acromegaly with 'normal' serum growth hormone levels. Clinical features, diagnosis and results of transsphenoidal microsurgery.

Among 216 consecutive patients with growth hormone secreting pituitary adenomas who underwent primary neurosurgical treatment at the University of Erlangen-Nürnberg, 8 cases of acromegaly with 'normal' basal growth hormone levels (less than or equal to 5 ng/ml) were seen. They all had the typical clinical features of acromegaly, exhibited an abnormal growth hormone secretion following an oral glucose load, and had markedly elevated somatomedin C levels. The GRH- and TRH/GnRH-tests were not found helpful in establishing the diagnosis. Neuroradiology could demonstrate a pituitary adenoma in all of the patients. Following transsphenoidal microsurgical resection of the tumours, growth hormone secretion during oral glucose tolerance testing was normalised in 7 of the 8 patients. Immunohistology and explant culture studies documented growth hormone secreting pituitary adenomas in all cases. The authors conclude that even the finding of repetitive 'normal' (less than or equal to 5 ng/ml) serum GH levels does not exclude active acromegaly and when the clinical diagnosis of acromegaly is suspected, dynamic endocrine testing may reveal abnormal secretion patterns of GH in these cases. Transsphenoidal microsurgical resection of a pituitary adenoma offers a good chance of clinical and endocrinological remission in these cases.

Acromegaly↗
PubMed1992

[Prognostic factors and results after the combined surgical and radiotherapy treatment of ependymomas].

Between 1978 and 1991, 31 patients with primary (n = 28) and recurrent (n = 3) ependymoma received external radiation after initial surgery. There were 26 cases of intracranial and five cases of spinal ependymoma. Histological grading revealed low-grade in 23 and high-grade tumors in eight patients. Craniospinal irradiation was given to 13 of 28 patients, whole cranial radiation with boost to posterior fossa in three and local treatment to twelve patients. Six of 28 patients received chemotherapy. Dose to the primary, tumor localisation, grading and extend of surgery did not significantly impact on survival and relapse-free survival. Age was a marginally significant prognostic factor for survival. In patients with intracranial ependymoma (n = 24) survival and relapse-free survival at five years were 54% and 42%, respectively. Patterns of recurrence showed a local recurrence alone in eight, a CNS-relapse with local recurrence in four and local recurrence with distant metastases in one case. Spinal seeding occurred in two of 13 after craniospinal irradiation and two of twelve patients after local treatment. The main problem in the treatment of ependymoma remains local control, the use of spinal irradiation does not seem to improve treatment results.

Adolescent↗
PubMed1992

Surgical management of acromegaly.

Surgery is generally the primary therapy of choice in acromegaly, and the predominantly used transsphenoidal approach has proved to be efficient and safe. Surgical results are dependent on preoperative tumor size and extension and preoperative growth hormone levels. Invasion appears to be the most important factor in predicting surgical outcome. Growth hormone levels can be normalized in 71% of all cases and in more than 80% of microadenomas. Persistent growth hormone excess may require reoperation, radiotherapy, or medical treatment. With close interdisciplinary cooperation of neurosurgeons, endocrinologists, and radiotherapists, nearly all acromegalic patients can be successfully treated today.

Acromegaly↗
PubMed1991

Long-term follow-up results in hormonally active pituitary adenomas after primary successful transsphenoidal surgery.

The long-term results of transsphenoidal surgery for hormonally active pituitary adenomas were assessed in 3 follow-up studies. Eight out of 50 patients with microprolactinomas developed a persisting postoperative re-increase of prolactin levels during an average follow-up period of 4.1 years. None of the 43 acromegalic patients who had achieved a suppression of growth hormone to below 2 ng/ml during an oral glucose load shortly after surgery relapsed. However, when the remission criterion was only based on basal growth hormone below 5 ng/ml 4 out of 61 patients showed a re-increase of growth hormone levels to persistently elevated values during an average follow-up period of 6.1 years. 14 out of 66 patients followed-up for an average of 8.2 years after successful primary microadenomectomy for Cushing's disease developed recurrent hypercortisolism as documented by an abnormal suppression of cortisol after oral low dose dexamethasone.

Acromegaly↗
PubMed1991

Effect of dopamine agonist medication on prolactin producing pituitary adenomas. A morphological study including immunocytochemistry, electron microscopy and in situ hybridization.

Conventional light microscopy, immunocytochemistry, electron microscopy and in situ hybridization were used to evaluate the effect of dopamine agonists (bromocriptine-LAR and bromocriptine) on the morphology of surgically removed prolactin (PRL)-producing pituitary adenomas. Dopamine agonist therapy resulted in decrease of serum PRL, clinical improvement and tumour shrinkage. Using light and electron microscopy cellular atrophy, interstitial and perivascular fibrosis were noted; in several tumours connective tissue accumulation was pronounced. The cellular response was not uniform. In some adenomas populations of large cells and small cells were distinguished. The large cells contained immunoreactive PRL and expressed the PRL gene indicating resistance to dopamine agonists. It appears that these cells retained the potential to secrete PRL and proliferate despite exposure to dopamine agonists. In the small cells, PRL immunoreactivity and PRL gene expression decreased providing evidence that both PRL release and synthesis were blocked. Small cells can persist in tumours after discontinuation of dopamine agonist medication suggesting these small cells are irreversibly suppressed and are not capable of regaining their endocrine function and proliferative capability. The formation of irreversibly suppressed PRL cells may explain why some PRL-producing adenomas do not recur after withdrawal of dopamine agonists.

Adenoma↗
PubMed1991

Recurrence following transsphenoidal surgery for acromegaly.

The long-term results of transsphenoidal adenomectomy and the incidence of possible recurrences were studied in 61 patients who had normal basal serum growth hormone (GH) levels 1 week after surgery. The patients were followed up for an average of 6.0 years (range: 1.5-14.0 years) by repeated measurements of GH, oral glucose tolerance testing (OGTT) and at the last follow-up visit also by assaying somatomedin C levels. In 4 of the patients, the basal GH levels had increased to values above 5 ng/ml. In 43 patients, a normal suppression of GH during an oral glucose load was observed shortly after surgery. In only 2 of these cases did a transiently inadequate suppression develop during the follow-up period, although clinical acromegaly did not recur and the somatomedin C levels remained normal. It is concluded that recurrence of active acromegaly is unlikely to occur in patients who achieve a normal glucose-induced suppression of GH levels shortly after adenomectomy. As such, an OGTT provides better prognostic information than basal human GH level measurements and may give a clearer and earlier indication of surgical success.

Acromegaly↗
PubMed1991

Pituitary microcirculation: physiological aspects and clinical implications. A laser-Doppler flow study during transsphenoidal adenomectomy.

The anterior and posterior pituitary lobes (AL and PL, respectively) are assumed to differ in the type of vascular supply and structure of their microvascular networks. Animal experiments have shown that the pituitary microvascular flow differs between the two lobes, being extremely high in the PL and low in the AL. For technical reasons, it has hitherto not been possible to study pituitary microflow in humans. Laser-Doppler flowmetry (LDF) is now a well-established method for real-time monitoring of microcirculation, applicable also in humans. In a prospective clinical study, the microflow in the AL and PL was measured during transsphenoidal microsurgery in 52 patients with adenomas of different size, growth characteristics, and endocrinological activity. The mean microflow in the PL (177.7 +/- 12.6 [flux]) was found to be about six times higher than that in the AL (27.4 +/- 2.7 [flux]). No difference in the laser-Doppler fractional volume of the lobes could be detected (0.73 +/- 0.06 [] vs. 0.77 +/- 0.07 [], where [] designates the ratio of the alternating current output to the direct current output signals). Microflow within the pituitary lobes was influenced neither by the histological type nor the size of the adenoma. Additionally, LDF signal-averaging triggered by the electrocardiogram allowed detection of different characteristic pulsatile microvascular flow patterns in the AL and PL. Our findings provide strong physiological support for the idea that the angioarchitecture of the pituitary lobes differs. With this method, the AL and PL can be identified objectively during surgery. LDF might provide useful information concerning intraoperative surgical approach.

Adenoma↗
PubMed1990

Intraocular pressure in patients with Cushing's disease.

Externally applied corticosteroids increase the intraocular pressure in one-third of the general population. We evaluated the intraocular pressure in 62 patients with endogenously elevated serum cortisol levels due to hypothalamic pituitary-dependent Cushing's disease. All patients underwent transphenoidal microsurgical sella exploration within 4 years after the onset of subjective symptoms. The intraocular pressure (preoperative mean, 14.9 +/- 3.5 mm Hg) exceeded 21 mm Hg in four eyes before surgery and in one eye after surgery (postoperative mean, 14.3 +/- 2.8 mm Hg). In patients attaining postoperative remission and whose pressure readings were taken at least 3 months after surgery, the postoperative intraocular pressure was significantly (P = 0.04) lower than that measured preoperatively (14.2 +/- 2.7 vs 13.0 +/- 2.0 mm Hg). Biomorphometry of the optic disc topography and the retinal nerve-fiber layer in 19 patients revealed no glaucomatous changes. In contrast to topically applied corticosteroids, endogenously elevated serum cortisol levels in patients with hypothalamic pituitary-dependent Cushing's disease increased intraocular pressure only slightly, with no great risk of glaucomatous optic nerve damage.

Adolescent↗
PubMed1990

Observations on the pathophysiology of Nelson's syndrome: a report of three cases.

Nelson's syndrome is generally regarded as an unusual sequela of primary bilateral adrenalectomy when performed for Cushing's disease. It is classically defined by cutaneous hyperpigmentation, considerably elevated adrenocorticotropic hormone (ACTH) levels, and an enlarged sella turcica. In this report, we present three cases initially treated by transsphenoidal sellar exploration for Cushing's disease. In two of these cases, remission of hypercortisolism did not occur after the initial pituitary exploration. A microadenomectomy was performed in one case and, in the other, no microadenoma was found. In both, Nelson's syndrome occurred after adrenalectomy. A second transsphenoidal operation and radiotherapy were required to control tumor growth. In another case, transsphenoidal adenomectomy of an ACTH-secreting tumor initially led to a remission of hypercortisolism for 4 years, but recurrent Cushing's disease necessitated adrenalectomy, and again Nelson's syndrome occurred. The documentation of a pre-existing ACTH-secreting basophilic pituitary microadenoma before adrenalectomy, as seen in two of our cases, has not been previously reported, and these observations of "non-classical" courses have major implications for the pathophysiology of Nelson's syndrome.

Adenoma↗
PubMed1990

[Effect of neurosurgical interventions on serum levels of the essential trace elements zinc and copper--a perioperative study].

The serum-concentrations of the trace-elements zinc and copper were assessed before and after neurosurgical interventions in 60 patients. On the day of surgery the mean values of zinc and copper showed a significant decrease, but had reached their preoperative level one week later. While a influence of dexamethasone on the serum zinc levels could not be deducted, the serum copper concentrations seem to be influenced by dexamethasone. These changes seem to be connected with the activation of the hypothalamus-pituitary-adrenal axis during surgical stress.

Abscess↗
PubMed1990

[Glaucoma in central hypothalamic-hypophyseal Cushing syndrome].

One third of a general population reacts to exogenously applied corticosteroids with an increase of intraocular pressure. In this study we investigated the influence of endogeneously elevated serum cortisol levels on the intraocular pressure and the presence of glaucomatous changes in the morphology of the optic disc and retinal nerve fiber layer. 15 patients with hypothalamic-pituitary Cushing's disease due to an ACTH producing adenoma of the pituitary gland and undergoing transphenoidal microsurgical exploration of the sella turcica were ophthalmologically examined pre- and post-operatively. Subjective symptoms had been noticed not earlier than four years before operation. Intraocular pressure was preoperatively and postoperatively within the normal range for all but one patient with readings of 23/23 mm Hg preoperatively. In the subgroup with endocrinological remission the intraocular pressure readings decreased postoperatively. Photography of the retinal nerve fiber layer, morphometry of 15 degree color stereo optic disc diapositives, and perimetry revealed no changes typical for glaucoma. In 4 patients the retinal nerve fiber bundles were remarkably well visible. We conclude that patients suffering from hypothalamic-pituitary Cushing's disease with endogeneously elevated serum cortisol levels and a duration of subjective symptoms of less than 4 years run a lower risk of developing glaucomatous damage than patients with topical administration of corticosteroids.

Adolescent↗
PubMed1989

Results of dynamic endocrine testing of hypothalamic pituitary function in patients with a primary "empty" sella syndrome.

A total of 52 patients (38 women, 14 men) with a primary "empty" sella syndrome underwent dynamic endocrine testing consisting of insulin-induced hypoglycaemia and a combined anterior pituitary stimulation test utilizing GnRH and TRH. The diagnosis of an "empty" sella turcica was made on the basis of thin collimation CT reconstructions and in addition either metrizamide cisternography or magnetic resonance (MR) imaging. Only 16 of the patients presented with endocrine problems. Hyperprolactinaemia was the most common endocrine disturbance detected, and was found in 17 individuals. Panhypopituitarism was found in 3 patients. Nine other patients had some degree of partial pituitary insufficiency, but only two of them required replacement therapy. However, 31 patients had no evidence of endocrine dysfunction.

Adult↗
PubMed1989

Endocrine disturbances in suprasellar germinomas.

The authors have investigated hypothalamic-pituitary function in 8 patients (aged 9-27 years) with surgically and histologically proven suprasellar germinomas. Diabetes insipidus was found in 7 patients. All the patients had hypogonadism and hypocortisolism as judged by dynamic endocrine testing. Hypothyroidism was found in 6. Moreover, growth hormone secretion, as assessed by insulin-induced hypoglycemia, was defective in all patients. Comparison of results of insulin-induced hypoglycemia testing and stimulation tests by CRH and GHRH suggested that all patients had a primary suprahypophyseal lesion rather than a primary pituitary defect. The authors conclude that suprasellar germinomas, although uncommon, should be included in the differential diagnosis of juvenile suprasellar tumours and in cases suggestive of idiopathic diabetes insipidus, even if neuroradiological investigation fails to demonstrate a discrete tumour.

Adolescent↗