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Michèle Le Dafniet, Anne-Marie Brandi, Michèle Kujas, Philippe Chanson and Françoise Peillon

Le Dafniet M, Brandi A-M, Kujas M, Chanson P, Peillon F. Thyrotropin-releasing hormone (TRH) binding sites and thyrotropin response to TRH are regulated by thyroid hormones in human thyrotropic adenomas. Eur J Endocrinol 1994:130:559–64. ISSN 0804–4643

In order to see whether, in thyrotropic adenomas with thyrotoxicosis, plasma thyroid hormones regulate the thyrotropin-releasing hormone (TRH) binding sites and the thyrotropin (TSH) response to TRH, we investigated: the presence of TRH binding sites in two cases of thyrotropic adenomas associated with hyperthyroidism and in one case of thyrotropic adenoma secondary to thyroid failure; and the in vitro effect, in a perifusion system, of triiodothyronine (T3) on the response of TSH to TRH in three cases of TSH-secreting adenomas associated with hyperthyroidism. The TRH binding sites were absent in the adenomas associated with high levels of circulating thyroid hormones, whereas they were present in the adenoma secondary to primary thyroid failure (K4 =47 nmol/l, Bmax = 40 nmol/ kg membrane proteins). In vitro, the three adenomas spontaneously released TSH in the perifusion medium (1.49 ±0.06 (mean ± sem), 7.25±0.12 and 16.73±0.36 mIU·−1·106 cells−1·2 min−1) and exhibited an ample TSH response to 10−7 mol/l TRH pulses. In two cases, tumoral secretion of fragments was compared with those of fragments maintained since the time of surgical removal in the presence of 10−8 mol/l T3. The TSH responses to TRH were abolished in the presence of T3 in these two cases. We conclude that thyrotropic adenomas associated with hyperthyroidism are still controlled in vivo by T3. In particular, T3 regulates the TSH response to TRH, probably via a down-regulation of the TRH binding sites.

Michèle Le Dafniet, Unité INSERM 223, Faculté de Médecine, Pitié-Salpêtrière, 105 Boulevard de l'Hôpital, 75013 Paris, France

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Sophie Brochier, Françoise Galland, Michèle Kujas, Fabrice Parker, Stephan Gaillard, Christian Raftopoulos, Jacques Young, Orsalia Alexopoulou, Dominique Maiter and Philippe Chanson

Context

Adequate postoperative management of nonfunctioning pituitary macroadenomas (NFMAs) remains a challenge for the clinician.

Objective

To identify predictive factors of NFMA relapse after initial surgery.

Patients and methods

This retrospective study included 142 patients operated for an NFMA in two academic centers (CHU Bicêtre in France and UCL St Luc in Belgium). The rate of tumor relapse, defined as recurrence after total surgical resection or regrowth of a surgical remnant, as well as predictive factors was analyzed.

Results

During a mean follow-up of 6.9 years, 10 out of 42 patients (24%) who had complete macroscopic resection of their tumor had recurrence, and 47 out of 100 patients (47%) with a surgical remnant experienced regrowth. The overall relapse rates were 25, 43, and 61% at 5, 10, and 15 years respectively. Invasion of the cavernous sinus, absence of immediate radiotherapy after the first neurosurgery, and immunohistochemical features of the tumor (mainly positive immunostaining for several hormones or for hormones other than gonadotropins) were independent risk factors for tumor relapse. Incomplete excision was only associated with relapse when invasion was withdrawn from the analysis, suggesting that these two factors are closely linked.

Conclusion

NFMAs frequently recur/regrow after initial surgery, particularly when tumor is invasive, precluding complete removal. Immunohistochemical features such as positive immunostaining for several hormones or for hormones other than gonadotropins could help to predict undesirable outcomes.

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Patrick Pagesy, Jacques Y. Li, Françoise Rentier-Delrue, Olivier Delalande, Yves Le Bouc, Michèle Kujas, Dominique Joubert(Bression), Joseph Martial and Françoise Peillon

Abstract.

Some patients with active acromegaly have elevated plasma IGF-I concentrations with only minimal elevation of plasma GH. We compared adenomatous GH and SRIH expression in 3 such patients (patients No. 1, 2 and 3; basal plasma GH level < 4 μg/l) and in 3 acromegalic patients with high basal plasma GH level (patients No. 4, 5 and 6; 51.7 ± 16.1 μg/l, mean ± sem). By immunocytochemistry, all the tumours proved to be somatotropic adenomas. At the ultrastructural level, signs of low secretory activity were observed in adenomas from patients No. 2 and 3. Perifused adenoma cells of patients No. 1, 2 and 3 released very little GH compared with those of patients No. 4, 5 and 6 (1± 0.37 vs 51.5± 34.1 μg · (10−6 cells) · min−1, p< 0.001). Adenoma SRIH content was 65.7 and 30.6 pg/mg proteins in patients No. 1 and 2, whereas it was undetectable in the others (patients No. 4, 5 and 6). Northern blot analysis showed that the GH gene was poorly expressed in the adenomas from patients No. 1, 2 and 3 compared with the adenomas from patients No. 4, 5 and 6. SRIH mRNA was detected in all 6 adenomas. However, the signal was more intense in the adenomas from patients No. 1, 2 and 3 than in those from patients No. 4, 5 and 6. In conclusion, because of the variability of the biosynthetic and secretory potential of the somatotropic adenomas, patients harbouring this type of pituitary tumours can exhibit a wide range of plasma GH levels. In acromegaly with minimal elevation of plasma GH, the synthesis of SRIH by the adenoma cells themselves could play a role in the inhibition of GH expression.