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A Rijnberk - One of the best experts on this subject based on the ideXlab platform.
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residual Pituitary Function after transsphenoidal hypophysectomy in dogs with Pituitary dependent hyperadrenocorticism
Journal of Endocrinology, 1997Co-Authors: B P Meij, J A Mol, M M Bevers, A RijnberkAbstract:Pituitary Function was assessed before and after transsphenoidal hypophysectomy in 39 dogs with Pituitary-dependent hyperadrenocorticism (PDH). Anterior Pituitary Function was investigated using combined administration of four hypophysiotropic releasing hormones (corticotropin-releasing hormone (CRH), GHRH, GnRH, and TRH) with measurements of ACTH, cortisol, GH, LH, prolactin (PRL), and TSH Pars intermedia Function was assessed by measurements of basal plasma alpha-MSH concentrations and adrenocortical Function by baseline urinary corticoid/creatinine ratios. At eight weeks after hypophysectomy basal plasma ACTH, cortisol, GH, LH, PRL, and TSH concentrations were significantly lower than before surgery. In seven dogs with elevated alpha-MSH concentrations, the values returned to the normal level after surgery. In the combined anterior Pituitary Function Test there were no plasma GH, LH, PRL, and TSH responses to stimulation, whereas plasma ACTH and cortisol responses were small but significant. Remission of hyperadrenocorticism was obtained in 35 dogs and recurrences occurred in 3 of these within 16 months postoperatively. At 8 weeks after hypophysectomy, these 3 dogs were not discernible, with respect to residual Pituitary and adrenocortical Function, from the 32 dogs with persisting remission. Urinary corticoid/creatinine ratios in the latter group of dogs did not increase during 22 months after hypophysectomy. In contrast to the presurgical findings, at 8 weeks after hypophysectomy there were significant positive correlations between baseline urinary corticoid/creatinine ratios and basal levels and responses for ACTH, indicating return to normal Function of the Pituitary-adrenocortical axis. It is concluded that among the adenohypophyseal cells present in the sella turcica after hypophysectomy, the corticotropes have a distinct behavior. Much more so than the other cell types, the unaffected corticotropes tend to remain Functional, or a repressed reserve fraction of corticotropes may become Functional. This may be due to the removal of the hypothalamic influence of a postulated corticotropin-release inhibiting factor or a diminished inhibitory influence of a postulated paracrine factor. The corticotropes may maintain normocorticism, but may also lead to mild recurrence after relatively long periods of remission.
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Assessment of a combined anterior Pituitary Function Test in beagle dogs: Rapid sequential intravenous administration of four hypothalamic releasing hormones
Domestic Animal Endocrinology, 1996Co-Authors: B P Meij, M M Bevers, H A W Hazewinkel, A RijnberkAbstract:Abstract A combined anterior Pituitary (CAP) Function Test was assessed in eight healthy male beagle dogs. The CAP Test consisted of sequential 30-second intravenous administrations of four hypothalamic releasing hormones in the following order and doses: 1 μg of corticotropin-releasing hormone (CRH)/kg, 1 μg of growth hormone-releasing hormone (GHRH)/kg, 10 μg of gonadotropinreleasing hormone (GnRH)/kg, and 10 μg of thyrotropin-releasing hormone (TRH)/kg. Plasma samples were assayed for adrenocorticotropin, cortisol, GH, luteinizing hormone (LH), and prolactin (PRL) at multiple times for 120 min after injection. Each releasing hormone was also administered separately in the same dose to the same eight dogs in order to investigate any interactions between the releasing hormones in the combined Function Test. Compared with separate administration, the combined administration of these four hypothalamic releasing hormones caused no apparent inhibition or synergism with respect to the responses to CRH, GHRH, and TRH. The combined administration of these four hypothalamic releasing hormones caused a 50% attenuation in LH response compared with the LH response to single GnRH administration. The side effects of the combined Test were confined to restlessness and nausea in three dogs, which disappeared within minutes after the administration of the releasing hormones. It is concluded that with the rapid sequential administration of four hypothalamic releasing hormones (CRH, GHRH, GnRH, and TRH), the adenohypophyseal responses are similar to those occurring with the single administration of these secretagogues, with the exception of the LH response, which is lower in the CAP Test than after single GnRH administration.
B P Meij - One of the best experts on this subject based on the ideXlab platform.
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residual Pituitary Function after transsphenoidal hypophysectomy in dogs with Pituitary dependent hyperadrenocorticism
Journal of Endocrinology, 1997Co-Authors: B P Meij, J A Mol, M M Bevers, A RijnberkAbstract:Pituitary Function was assessed before and after transsphenoidal hypophysectomy in 39 dogs with Pituitary-dependent hyperadrenocorticism (PDH). Anterior Pituitary Function was investigated using combined administration of four hypophysiotropic releasing hormones (corticotropin-releasing hormone (CRH), GHRH, GnRH, and TRH) with measurements of ACTH, cortisol, GH, LH, prolactin (PRL), and TSH Pars intermedia Function was assessed by measurements of basal plasma alpha-MSH concentrations and adrenocortical Function by baseline urinary corticoid/creatinine ratios. At eight weeks after hypophysectomy basal plasma ACTH, cortisol, GH, LH, PRL, and TSH concentrations were significantly lower than before surgery. In seven dogs with elevated alpha-MSH concentrations, the values returned to the normal level after surgery. In the combined anterior Pituitary Function Test there were no plasma GH, LH, PRL, and TSH responses to stimulation, whereas plasma ACTH and cortisol responses were small but significant. Remission of hyperadrenocorticism was obtained in 35 dogs and recurrences occurred in 3 of these within 16 months postoperatively. At 8 weeks after hypophysectomy, these 3 dogs were not discernible, with respect to residual Pituitary and adrenocortical Function, from the 32 dogs with persisting remission. Urinary corticoid/creatinine ratios in the latter group of dogs did not increase during 22 months after hypophysectomy. In contrast to the presurgical findings, at 8 weeks after hypophysectomy there were significant positive correlations between baseline urinary corticoid/creatinine ratios and basal levels and responses for ACTH, indicating return to normal Function of the Pituitary-adrenocortical axis. It is concluded that among the adenohypophyseal cells present in the sella turcica after hypophysectomy, the corticotropes have a distinct behavior. Much more so than the other cell types, the unaffected corticotropes tend to remain Functional, or a repressed reserve fraction of corticotropes may become Functional. This may be due to the removal of the hypothalamic influence of a postulated corticotropin-release inhibiting factor or a diminished inhibitory influence of a postulated paracrine factor. The corticotropes may maintain normocorticism, but may also lead to mild recurrence after relatively long periods of remission.
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transsphenoidal hypophysectomy in beagle dogs evaluation of a microsurgical technique
Veterinary Surgery, 1997Co-Authors: B P Meij, T S G A M Van Den Ingh, H A W Hazewinkel, G Voorhout, Johanna W Van T VerlaatAbstract:Objective— Assessment of a microsurgical technique for transsphenoidal hypophysectomy in dogs. Study Design— Prospective study using physical examination, Pituitary Function Testing, computed tomography (CT), and histological examination at autopsy. Animals or Sample Population— Eight laboratory beagle dogs. Methods— Pituitary Function was assessed before and at 10 weeks after hypophysectomy by combined administration of four releasing hormones (anterior Pituitary), administration of haloperidol (pars intermedia), and infusion of hypertonic saline (posterior Pituitary). Results— CT imaging enabled accurate preoperative localization of the Pituitary. Appropriate positioning and surgical technique facilitated exposure of the Pituitary and its extraction without hemorrhage. Postoperative recovery was generally uncomplicated. None of die eight dogs had somatotropic, gonadotropic, lactotropic, melanotropic, or posterior Pituitary responses to stimulation at 10 weeks after hypophysectomy. Four dogs (ACTH nonresponders) also had no cortico-tropic response and four (ACTH responders) had small but significant responses in the combined anterior Pituitary Function Test. Adrenocortical atrophy was more pronounced in the ACTH nonresponders man in the responders. No residual Pituitary tissue was found along the ventral hypothalamic diencephalon but nests of Pituitary cells were found embedded in fibrous tissue in the sella turcica. Conclusions— The surgical technique proved to be safe and effective. Microscopic nests of Pituitary cells in the sella turcica may be responsible for residual corticotropic response to hypophysiotropic stimulation after hypophysectomy. Clinical Relevance— The surgical technique may be used in the treatment of dogs with Pituitary-dependent hyperadrenocorticism. The corticotropic response is the most sensitive criterion in assessing completeness of hypophysectomy in dogs.
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Assessment of a combined anterior Pituitary Function Test in beagle dogs: Rapid sequential intravenous administration of four hypothalamic releasing hormones
Domestic Animal Endocrinology, 1996Co-Authors: B P Meij, M M Bevers, H A W Hazewinkel, A RijnberkAbstract:Abstract A combined anterior Pituitary (CAP) Function Test was assessed in eight healthy male beagle dogs. The CAP Test consisted of sequential 30-second intravenous administrations of four hypothalamic releasing hormones in the following order and doses: 1 μg of corticotropin-releasing hormone (CRH)/kg, 1 μg of growth hormone-releasing hormone (GHRH)/kg, 10 μg of gonadotropinreleasing hormone (GnRH)/kg, and 10 μg of thyrotropin-releasing hormone (TRH)/kg. Plasma samples were assayed for adrenocorticotropin, cortisol, GH, luteinizing hormone (LH), and prolactin (PRL) at multiple times for 120 min after injection. Each releasing hormone was also administered separately in the same dose to the same eight dogs in order to investigate any interactions between the releasing hormones in the combined Function Test. Compared with separate administration, the combined administration of these four hypothalamic releasing hormones caused no apparent inhibition or synergism with respect to the responses to CRH, GHRH, and TRH. The combined administration of these four hypothalamic releasing hormones caused a 50% attenuation in LH response compared with the LH response to single GnRH administration. The side effects of the combined Test were confined to restlessness and nausea in three dogs, which disappeared within minutes after the administration of the releasing hormones. It is concluded that with the rapid sequential administration of four hypothalamic releasing hormones (CRH, GHRH, GnRH, and TRH), the adenohypophyseal responses are similar to those occurring with the single administration of these secretagogues, with the exception of the LH response, which is lower in the CAP Test than after single GnRH administration.
M M Bevers - One of the best experts on this subject based on the ideXlab platform.
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residual Pituitary Function after transsphenoidal hypophysectomy in dogs with Pituitary dependent hyperadrenocorticism
Journal of Endocrinology, 1997Co-Authors: B P Meij, J A Mol, M M Bevers, A RijnberkAbstract:Pituitary Function was assessed before and after transsphenoidal hypophysectomy in 39 dogs with Pituitary-dependent hyperadrenocorticism (PDH). Anterior Pituitary Function was investigated using combined administration of four hypophysiotropic releasing hormones (corticotropin-releasing hormone (CRH), GHRH, GnRH, and TRH) with measurements of ACTH, cortisol, GH, LH, prolactin (PRL), and TSH Pars intermedia Function was assessed by measurements of basal plasma alpha-MSH concentrations and adrenocortical Function by baseline urinary corticoid/creatinine ratios. At eight weeks after hypophysectomy basal plasma ACTH, cortisol, GH, LH, PRL, and TSH concentrations were significantly lower than before surgery. In seven dogs with elevated alpha-MSH concentrations, the values returned to the normal level after surgery. In the combined anterior Pituitary Function Test there were no plasma GH, LH, PRL, and TSH responses to stimulation, whereas plasma ACTH and cortisol responses were small but significant. Remission of hyperadrenocorticism was obtained in 35 dogs and recurrences occurred in 3 of these within 16 months postoperatively. At 8 weeks after hypophysectomy, these 3 dogs were not discernible, with respect to residual Pituitary and adrenocortical Function, from the 32 dogs with persisting remission. Urinary corticoid/creatinine ratios in the latter group of dogs did not increase during 22 months after hypophysectomy. In contrast to the presurgical findings, at 8 weeks after hypophysectomy there were significant positive correlations between baseline urinary corticoid/creatinine ratios and basal levels and responses for ACTH, indicating return to normal Function of the Pituitary-adrenocortical axis. It is concluded that among the adenohypophyseal cells present in the sella turcica after hypophysectomy, the corticotropes have a distinct behavior. Much more so than the other cell types, the unaffected corticotropes tend to remain Functional, or a repressed reserve fraction of corticotropes may become Functional. This may be due to the removal of the hypothalamic influence of a postulated corticotropin-release inhibiting factor or a diminished inhibitory influence of a postulated paracrine factor. The corticotropes may maintain normocorticism, but may also lead to mild recurrence after relatively long periods of remission.
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Assessment of a combined anterior Pituitary Function Test in beagle dogs: Rapid sequential intravenous administration of four hypothalamic releasing hormones
Domestic Animal Endocrinology, 1996Co-Authors: B P Meij, M M Bevers, H A W Hazewinkel, A RijnberkAbstract:Abstract A combined anterior Pituitary (CAP) Function Test was assessed in eight healthy male beagle dogs. The CAP Test consisted of sequential 30-second intravenous administrations of four hypothalamic releasing hormones in the following order and doses: 1 μg of corticotropin-releasing hormone (CRH)/kg, 1 μg of growth hormone-releasing hormone (GHRH)/kg, 10 μg of gonadotropinreleasing hormone (GnRH)/kg, and 10 μg of thyrotropin-releasing hormone (TRH)/kg. Plasma samples were assayed for adrenocorticotropin, cortisol, GH, luteinizing hormone (LH), and prolactin (PRL) at multiple times for 120 min after injection. Each releasing hormone was also administered separately in the same dose to the same eight dogs in order to investigate any interactions between the releasing hormones in the combined Function Test. Compared with separate administration, the combined administration of these four hypothalamic releasing hormones caused no apparent inhibition or synergism with respect to the responses to CRH, GHRH, and TRH. The combined administration of these four hypothalamic releasing hormones caused a 50% attenuation in LH response compared with the LH response to single GnRH administration. The side effects of the combined Test were confined to restlessness and nausea in three dogs, which disappeared within minutes after the administration of the releasing hormones. It is concluded that with the rapid sequential administration of four hypothalamic releasing hormones (CRH, GHRH, GnRH, and TRH), the adenohypophyseal responses are similar to those occurring with the single administration of these secretagogues, with the exception of the LH response, which is lower in the CAP Test than after single GnRH administration.
Mirjam Christcrain - One of the best experts on this subject based on the ideXlab platform.
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anterior and posterior Pituitary Function Testing with simultaneous insulin tolerance Test and a novel copeptin assay
The Journal of Clinical Endocrinology and Metabolism, 2007Co-Authors: Mira Katan, Nils G Morgenthaler, Kashinath Dixit, Jonas Rutishauser, G Brabant, Beat Muller, Mirjam ChristcrainAbstract:Context: Posterior Pituitary Function in patients with suspected diabetes insipidus is usually assessed by a water deprivation Test. Alternatively, a nonosmotic stimulus such as hypoglycemia may be used to stimulate vasopressin [arginine vasopressin (AVP)] secretion. Plasma AVP measurement may aid in the diagnosis and, especially, differential diagnosis of diabetes insipidus and polydipsia. However, AVP measurement is cumbersome. Copeptin, the stable C-terminal glycopeptide of the AVP prohormone, is stoichiometrically secreted from the posterior Pituitary. Objective: The aim was to study the value of copeptin levels in the diagnosis of diabetes insipidus during insulin-induced hypoglycemia. Patients and Methods: A total of 38 patients were studied during insulin-induced hypoglycemia as part of a combined Pituitary Function Test for possible anterior Pituitary disease. There were 29 patients who had normal posterior Pituitary Function, and nine had centraldiabetesinsipidus.Bloodsamplingwasdonebeforeand30,45, and 90 min after iv insulin injection. Copeptin was measured with a new sandwich immunoassay. Results: Patients with intact posterior Pituitary Function had basal copeptin levels of 3.7 1.5 pM, with a maximal increase to 11.1 4.6 pM 45 min after insulin injection. Copeptin levels in patients with diabetes insipidus were 2.4 0.5 pM before insulin injection, with a maximum increase to 3.7 0.7 pM. Both basal and stimulated copeptin levels were lower in patients with diabetes insipidus as compared with patients with intact posterior Pituitary Function. A stimulated copeptin level 45 min after insulin injection of less than 4.75 pM had an optimal diagnostic accuracy to detect diabetes insipidus. Conclusion: Copeptin measurement may be used to assess posterior together with anterior Pituitary Function during insulin-induced hypoglycemia. (J Clin Endocrinol Metab 92: 2640–2643, 2007)
H A W Hazewinkel - One of the best experts on this subject based on the ideXlab platform.
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transsphenoidal hypophysectomy in beagle dogs evaluation of a microsurgical technique
Veterinary Surgery, 1997Co-Authors: B P Meij, T S G A M Van Den Ingh, H A W Hazewinkel, G Voorhout, Johanna W Van T VerlaatAbstract:Objective— Assessment of a microsurgical technique for transsphenoidal hypophysectomy in dogs. Study Design— Prospective study using physical examination, Pituitary Function Testing, computed tomography (CT), and histological examination at autopsy. Animals or Sample Population— Eight laboratory beagle dogs. Methods— Pituitary Function was assessed before and at 10 weeks after hypophysectomy by combined administration of four releasing hormones (anterior Pituitary), administration of haloperidol (pars intermedia), and infusion of hypertonic saline (posterior Pituitary). Results— CT imaging enabled accurate preoperative localization of the Pituitary. Appropriate positioning and surgical technique facilitated exposure of the Pituitary and its extraction without hemorrhage. Postoperative recovery was generally uncomplicated. None of die eight dogs had somatotropic, gonadotropic, lactotropic, melanotropic, or posterior Pituitary responses to stimulation at 10 weeks after hypophysectomy. Four dogs (ACTH nonresponders) also had no cortico-tropic response and four (ACTH responders) had small but significant responses in the combined anterior Pituitary Function Test. Adrenocortical atrophy was more pronounced in the ACTH nonresponders man in the responders. No residual Pituitary tissue was found along the ventral hypothalamic diencephalon but nests of Pituitary cells were found embedded in fibrous tissue in the sella turcica. Conclusions— The surgical technique proved to be safe and effective. Microscopic nests of Pituitary cells in the sella turcica may be responsible for residual corticotropic response to hypophysiotropic stimulation after hypophysectomy. Clinical Relevance— The surgical technique may be used in the treatment of dogs with Pituitary-dependent hyperadrenocorticism. The corticotropic response is the most sensitive criterion in assessing completeness of hypophysectomy in dogs.
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Assessment of a combined anterior Pituitary Function Test in beagle dogs: Rapid sequential intravenous administration of four hypothalamic releasing hormones
Domestic Animal Endocrinology, 1996Co-Authors: B P Meij, M M Bevers, H A W Hazewinkel, A RijnberkAbstract:Abstract A combined anterior Pituitary (CAP) Function Test was assessed in eight healthy male beagle dogs. The CAP Test consisted of sequential 30-second intravenous administrations of four hypothalamic releasing hormones in the following order and doses: 1 μg of corticotropin-releasing hormone (CRH)/kg, 1 μg of growth hormone-releasing hormone (GHRH)/kg, 10 μg of gonadotropinreleasing hormone (GnRH)/kg, and 10 μg of thyrotropin-releasing hormone (TRH)/kg. Plasma samples were assayed for adrenocorticotropin, cortisol, GH, luteinizing hormone (LH), and prolactin (PRL) at multiple times for 120 min after injection. Each releasing hormone was also administered separately in the same dose to the same eight dogs in order to investigate any interactions between the releasing hormones in the combined Function Test. Compared with separate administration, the combined administration of these four hypothalamic releasing hormones caused no apparent inhibition or synergism with respect to the responses to CRH, GHRH, and TRH. The combined administration of these four hypothalamic releasing hormones caused a 50% attenuation in LH response compared with the LH response to single GnRH administration. The side effects of the combined Test were confined to restlessness and nausea in three dogs, which disappeared within minutes after the administration of the releasing hormones. It is concluded that with the rapid sequential administration of four hypothalamic releasing hormones (CRH, GHRH, GnRH, and TRH), the adenohypophyseal responses are similar to those occurring with the single administration of these secretagogues, with the exception of the LH response, which is lower in the CAP Test than after single GnRH administration.