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  • Author: M Buchfelder x
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A Baur, M Buchfelder and J Kohrle

OBJECTIVE: Local 5'-deiodination of l-thyroxine (T(4)) to active thyroid hormone 3,3',5-tri-iodothyronine (T(3)) catalyzed by the two 5'-deiodinase enzymes (D1 and D2) regulates various T(3)-dependent functions in the anterior pituitary and has been well studied in rodents. Only limited information about deiodinase expression and its cellular distribution in human anterior pituitaries is available. DESIGN: We examined 5'-deiodinase enzyme activities in pituitary adenomas (18 non-functioning, seven TSH-producing, one GH- and TSH-producing, five GH-producing, eight prolactin (PRL)-producing, two adenomas each from patients with Cushing's disease and Nelson's syndrome) and three normal anterior pituitaries. METHODS: Activities were measured as release of (125)I(-) from tyrosyl-ring labeled reverse T(3) with or without propylthiouracil, a potent inhibitor of D1 which does not influence D2 activities. RESULTS: Most of the adenomas and normal tissues expressed both isoenzymes, with D2 activity higher than D1. In a few tissues D1 activity was higher than D2 and some tissues did not express D1 activity at all. Highest activities of both enzymes were found in TSH- and PRL-producing adenomas but absolute activities and the D1/D2 ratio were variable in the same kind of tumor in different patients. CONCLUSION: The finding that all examined tissues expressed 5'-deiodinase activity, most of them expressing both isoenzymes, implies that both enzymes are still active in tumors and that local deiodination is important for the function and feedback regulation of human anterior pituitary.

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M. Buchfelder, R. Fahlbusch, M. Walther and K. Mann

Abstract. The authors have investigated hypothalamicpituitary 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 supra-hypohypophyseal 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.

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W. SCHOTT, M. BUCHFELDER, U. SCHRELL and R. FAHLBUSCH

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M. BUCHFELDER, B. BÖHM, U. SCHRELL, J. PICHL and R. FAHLBUSCH

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S. BROCKMEIER, U. SCHRELL, M. BUCHFELDER and R. FAHLBUSCH

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J. PICHL, U. SCHRELL, M. BUCHFELDER and R. FAHLBUSCH

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M. BUCHFELDER, S. BROCKMEIER, U. SCHRELL, J. PICHL and R. FAHLBUSCH

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I Schreiber, M Buchfelder, M Droste, K Forssmann, K Mann, B Saller and C J Strasburger

Objective: The GH receptor antagonist pegvisomant is a highly effective new treatment option in acromegaly. The German Pegvisomant Observational Study (GPOS) was started to monitor long-term safety and efficacy of pegvisomant as prescribed in clinical practice.

Design: GPOS is an observational, multi-center, surveillance study, which comprises non-interventional data collection.

Methods: Of the 229 patients included in the study, 90.4% had previous pituitary surgery, 43.2% were treated by radiation therapy, and 94.3% had previous medical therapy for acromegaly that had been discontinued mainly due to persistent IGF-I elevation or side effects. The intention-to-treat population included 177 patients with at least one post-baseline efficacy measurement.

Results: IGF-I levels decreased from 1.75±0.91-fold the upper limit of normal at baseline to 1.05± 0.62 at the 6-month visit, 0.96±0.60 at the 12-month visit, and to 0.89±0.41-fold after 24 months (P<0.0001). Mean duration of pegvisomant therapy was 51.8±35.8 weeks (median=51.9 weeks). IGF-I was normalized in 64.4% at 6 months with a median dose of 15.0 mg/day, in 70.9% at 12 months, and in 76.3% at 24 months. Fasting glucose levels improved from 114.4±45.9 to 101.5± 42.8 mg/dl after 6 months (P<0.01) and to 100.6±33.2 mg/ml after 12 months (P<0.01). General physical condition measured by specific signs and symptoms score improved significantly. Adverse events occurring in >1% were injection site reactions in 7.4%, elevated liver enzymes (>3 times of normal) in 5.2% (3.1% spontaneously normalized during continued treatment), reported increase of pituitary tumor volume in 5.2% (which was verified in 3.1%), and headache in 1.7%.

Conclusions: Pegvisomant is generally well tolerated with a safety profile similar to that reported in clinical trials and can effectively reduce IGF-I in patients with acromegaly refractory to conventional therapy.