The Experts below are selected from a list of 84 Experts worldwide ranked by ideXlab platform
B P Meij - One of the best experts on this subject based on the ideXlab platform.
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plasma profiles of adrenocorticotropic hormone cortisol alpha melanocyte stimulating hormone and growth hormone in dogs with pituitary dependent hyperadrenocorticism before and after Hypophysectomy
Journal of Endocrinology, 2006Co-Authors: J M Hanson, H S Kooistra, J A Mol, E Teske, B P MeijAbstract:The 6-h plasma profiles of adrenocorticotropic hormone (ACTH), cortisol, alpha-melanocyte-stimulating hormone (alpha-MSH), and GH were studied in 17 dogs with pituitary-dependent hyperadrenocorticism (PDH) before and after Hypophysectomy. The aim of the study was to investigate the relation between the hormone profile characteristics and recurrence of PDH after surgery. The hormones were secreted in a pulsatile fashion. The basal plasma cortisol concentration and area under the curve (AUC) for cortisol were significantly higher in the PDH cases than in eight controls. The characteristics of the plasma profiles of ACTH and alpha-MSH were not significantly different between the PDH cases and the controls. In the PDH cases, less GH was secreted in pulses than in the controls, but the difference was not significant. The basal plasma cortisol concentration, the AUC for ACTH and cortisol, and the pulse frequency of ACTH and cortisol decreased significantly after Hypophysectomy for the group of PDH cases. The basal plasma concentrations of ACTH and alpha-MSH, the AUC for alpha-MSH, and the characteristics of the plasma GH profiles of the PDH cases remained unchanged after Hypophysectomy. No pulses of alpha-MSH were observed after Hypophysectomy. The co-occurrence between the ACTH and cortisol pulses decreased significantly with Hypophysectomy. The postoperative pulse frequency of ACTH was the only characteristic with predictive value for the recurrence of PDH after Hypophysectomy. The results of this study demonstrate that ACTH, cortisol, alpha-MSH, and GH are secreted in a pulsatile fashion in dogs with PDH. Hypophysectomy effectively reduces the secretion of ACTH and cortisol. The presence of ACTH pulses after Hypophysectomy is a risk factor for the recurrence of hyperadrenocorticism.
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efficacy of transsphenoidal Hypophysectomy in treatment of dogs with pituitary dependent hyperadrenocorticism
Journal of Veterinary Internal Medicine, 2005Co-Authors: J M Hanson, H S Kooistra, E Teske, Martine M Van T Hoofd, G Voorhout, B P MeijAbstract:The long-term survival, disease-free fractions, and the complications of Hypophysectomy in 150 dogs with pituitary-dependent hyperadrenocorticism (PDH) were examined in a prospective study. Long-term survival and disease-free fractions in relation to pituitary size were analyzed by the Kaplan-Meijer estimate procedure. The 1-, 2-, 3-, and 4-year estimated survival rates were 84% (95% confidence interval [CI], 76-89%), 76% (67-83%), 72% (62-79%), and 68% (55-77%), respectively. Treatment failures included procedure-related mortalities (12 dogs) and incomplete hypophysectomies (9 dogs). The 1-, 2-, 3-, and 4-year estimated relapse-free fractions were 88% (CI: 80-93%), 75% (64-83%), 66% (54-76%), and 58% (45-70%), respectively. Postoperative reduction of tear production (58 eyes in 47 dogs) was often reversible but remained low until death in 11 eyes of 10 dogs. Central diabetes insipidus (CDI) occurred more frequently (62%) in dogs with enlarged pituitaries than in dogs with nonenlarged pituitaries (44%). Survival and disease-free fractions after Hypophysectomy were markedly higher in dogs with nonenlarged pituitaries than in dogs with enlarged pituitaries. Transsphenoidal Hypophysectomy is an effective treatment for PDH in dogs. The survival and disease-free fractions after Hypophysectomy decrease and the incidence of CDI increases with increasing pituitary size. Therefore, early diagnosis of PDH is important and transsphenoidal Hypophysectomy is expected to have the best outcome when used as primary treatment for dogs with nonenlarged or moderately enlarged pituitaries.
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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 pituitary function after transsphenoidal Hypophysectomy in beagle dogs
Domestic Animal Endocrinology, 1997Co-Authors: B P Meij, J A Mol, T S G A M Van Den Ingh, M M Bevers, H A W Hazewinkel, A RijnberkAbstract:Abstract Pituitary function was assessed in healthy adult beagle dogs before and after Hypophysectomy. Anterior pituitary function was tested by use of the combined anterior pituitary (CAP) function test, which consisted of sequential 30-sec intravenous injections of four hypothalamic releasing hormones, in the following order and doses: 1 μg of cortrticotropin-releasing hormone (CRH)/kg, 1 μg of growth hormone-releasing hormone (GHRH)/kg, 10 μg of gonadotropin-releasing hormone (GnRH)/kg, and 10 μg of thyrotropin-releasing hormone (TRH)/kg. Plasma samples were assayed for adrenocorticotropin (ACTH), cortisol, GH, luteinizing hormone (LH), and prolactin (PRL) at multiple times for 120 min after injection. Pars intermedia function was assessed by the α-melanotropin (α-MSH) response to the intravenous injection of the dopamine antagonist haloperidol in a dosage of 0.2 mg/kg. Posterior pituitary function was assessed by the plasma vasopressin (AVP) response to the intravenous infusion of 20% saline. Basal plasma ACTH, cortisol, thyroxine, LH, PRL, and AVP concentrations were significantly lower at 10 wk after Hypophysectomy than before Hypophysectomy. In the CAP test and the haloperidol test, the peaks for the plasma concentrations of ACTH, cortisol, GH, LH, PRL, and α-MSH occurred within 45 min after injection. At 2 and 10 wk after Hypophysectomy, there were no responses of plasma GH, LH, PRL, and α-MSH to stimulation. In four of eight hypophysectomized dogs, there were also no plasma ACTH and cortisol responses, whereas in the other four dogs, plasma ACTH and cortisol responses were significantly attenuated. The basal plasma ACTH and cortisol concentrations were significantly lower in the corticotropic nonresponders than in the responders. Plasma AVP responses were completely abolished by Hypophysectomy, although water intake by the dogs was normal. Histopathological examinations at 10 wk after Hypophysectomy revealed that adrenocortical atrophy was much more pronounced in the corticotropic nonresponders than in the responders. No residual pituitary tissue was found along the ventral hypothalamic diencephalon. However, in all hypophysectomized dogs that were investigated, islets of pituitary cells were found embedded in fibrous tissue in the sella turcica. A significant positive correlation was found between the number of ACTH-immunopositive cells and the ACTH increment in the CAP test at 10 wk after Hypophysectomy. It is concluded that 1) stimulation of the anterior pituitary with multiple hypophysiotropic hormones, stimulation of the pars intermedia with a dopamine antagonist, and stimulation of the neurohypophysis with hypertonic saline do not cause side effects that would prohibit routine use, 2) in the routine stimulation of the anterior pituitary and the pars intermedia, blood sampling can be confined to the first 45 min, 3) the ACTH and cortisol responses to hypophysiotropic stimulation are the most sensitive indicators for residual pituitary function after Hypophysectomy, 4) small islets of pituitary cells in the sella turcica, containing corticotropic cells, are the most likely source of the attenuated corticotropic response that may occur after Hypophysectomy, and 5) residual AVP release from the hypothalamus after Hypophysectomy is sufficient to prevent diabetes insipidus, despite the fact that the AVP response to hypertonic saline infusion is completely abolished.
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 pituitary function after transsphenoidal Hypophysectomy in beagle dogs
Domestic Animal Endocrinology, 1997Co-Authors: B P Meij, J A Mol, T S G A M Van Den Ingh, M M Bevers, H A W Hazewinkel, A RijnberkAbstract:Abstract Pituitary function was assessed in healthy adult beagle dogs before and after Hypophysectomy. Anterior pituitary function was tested by use of the combined anterior pituitary (CAP) function test, which consisted of sequential 30-sec intravenous injections of four hypothalamic releasing hormones, in the following order and doses: 1 μg of cortrticotropin-releasing hormone (CRH)/kg, 1 μg of growth hormone-releasing hormone (GHRH)/kg, 10 μg of gonadotropin-releasing hormone (GnRH)/kg, and 10 μg of thyrotropin-releasing hormone (TRH)/kg. Plasma samples were assayed for adrenocorticotropin (ACTH), cortisol, GH, luteinizing hormone (LH), and prolactin (PRL) at multiple times for 120 min after injection. Pars intermedia function was assessed by the α-melanotropin (α-MSH) response to the intravenous injection of the dopamine antagonist haloperidol in a dosage of 0.2 mg/kg. Posterior pituitary function was assessed by the plasma vasopressin (AVP) response to the intravenous infusion of 20% saline. Basal plasma ACTH, cortisol, thyroxine, LH, PRL, and AVP concentrations were significantly lower at 10 wk after Hypophysectomy than before Hypophysectomy. In the CAP test and the haloperidol test, the peaks for the plasma concentrations of ACTH, cortisol, GH, LH, PRL, and α-MSH occurred within 45 min after injection. At 2 and 10 wk after Hypophysectomy, there were no responses of plasma GH, LH, PRL, and α-MSH to stimulation. In four of eight hypophysectomized dogs, there were also no plasma ACTH and cortisol responses, whereas in the other four dogs, plasma ACTH and cortisol responses were significantly attenuated. The basal plasma ACTH and cortisol concentrations were significantly lower in the corticotropic nonresponders than in the responders. Plasma AVP responses were completely abolished by Hypophysectomy, although water intake by the dogs was normal. Histopathological examinations at 10 wk after Hypophysectomy revealed that adrenocortical atrophy was much more pronounced in the corticotropic nonresponders than in the responders. No residual pituitary tissue was found along the ventral hypothalamic diencephalon. However, in all hypophysectomized dogs that were investigated, islets of pituitary cells were found embedded in fibrous tissue in the sella turcica. A significant positive correlation was found between the number of ACTH-immunopositive cells and the ACTH increment in the CAP test at 10 wk after Hypophysectomy. It is concluded that 1) stimulation of the anterior pituitary with multiple hypophysiotropic hormones, stimulation of the pars intermedia with a dopamine antagonist, and stimulation of the neurohypophysis with hypertonic saline do not cause side effects that would prohibit routine use, 2) in the routine stimulation of the anterior pituitary and the pars intermedia, blood sampling can be confined to the first 45 min, 3) the ACTH and cortisol responses to hypophysiotropic stimulation are the most sensitive indicators for residual pituitary function after Hypophysectomy, 4) small islets of pituitary cells in the sella turcica, containing corticotropic cells, are the most likely source of the attenuated corticotropic response that may occur after Hypophysectomy, and 5) residual AVP release from the hypothalamus after Hypophysectomy is sufficient to prevent diabetes insipidus, despite the fact that the AVP response to hypertonic saline infusion is completely abolished.
J M Hanson - One of the best experts on this subject based on the ideXlab platform.
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The Prognostic Value of Perioperative Profiles of ACTH and Cortisol for Recurrence after Transsphenoidal Hypophysectomy in Dogs with Corticotroph Adenomas
Journal of Veterinary Internal Medicine, 2015Co-Authors: S. J. Van Rijn, D. Zierikzee, J M Hanson, Louis C Penning, Marianna A. Tryfonidou, Hans S. Kooistra, Björn P. MeijAbstract:BACKGROUND: Transsphenoidal Hypophysectomy is an effective treatment for dogs with pituitary-dependent hypercortisolism (PDH). However, long-term recurrence of hypercortisolism is a well-recognized problem, indicating the need for reliable prognostic indicators.\n\nOBJECTIVES: The aim of this study was to evaluate the prognostic value of perioperative plasma ACTH and cortisol concentrations for identifying recurrence of hypercortisolism after transsphenoidal Hypophysectomy.\n\nANIMALS: A total of 112 dogs with PDH that underwent transsphenoidal Hypophysectomy met the inclusion criteria of the study.\n\nMETHODS: Hormone concentrations were measured preoperatively and 1-5 hours after surgery. Both absolute hormone concentrations and postoperative concentrations normalized to preoperative concentrations were included in analyses. The prognostic value of hormone concentrations was studied with Cox's proportional hazard analysis.\n\nRESULTS: Median follow-up and disease-free period were 1096 days and 896 days, respectively. Twenty-eight percent of patients had recurrence, with a median disease-free period of 588 days. Both absolute and normalized postoperative cortisol concentrations were significantly higher in dogs with recurrence than in dogs without recurrence. High ACTH 5 hours after surgery, high cortisol 1 and 4 hours after surgery, high normalized ACTH 3 hours after surgery, high normalized cortisol 4 hours after surgery and the random slope of cortisol were associated with a shorter disease-free period.\n\nCONCLUSIONS AND CLINICAL IMPORTANCE: Individual perioperative hormone curves provide valuable information about the risk of recurrence after Hypophysectomy. However, because no single cutoff point could be identified, combination with other variables, such as the pituitary height/brain area (P/B) ratio, is still needed to obtain a good estimate of the risk for recurrence of hypercortisolism after Hypophysectomy.
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plasma profiles of adrenocorticotropic hormone cortisol alpha melanocyte stimulating hormone and growth hormone in dogs with pituitary dependent hyperadrenocorticism before and after Hypophysectomy
Journal of Endocrinology, 2006Co-Authors: J M Hanson, H S Kooistra, J A Mol, E Teske, B P MeijAbstract:The 6-h plasma profiles of adrenocorticotropic hormone (ACTH), cortisol, alpha-melanocyte-stimulating hormone (alpha-MSH), and GH were studied in 17 dogs with pituitary-dependent hyperadrenocorticism (PDH) before and after Hypophysectomy. The aim of the study was to investigate the relation between the hormone profile characteristics and recurrence of PDH after surgery. The hormones were secreted in a pulsatile fashion. The basal plasma cortisol concentration and area under the curve (AUC) for cortisol were significantly higher in the PDH cases than in eight controls. The characteristics of the plasma profiles of ACTH and alpha-MSH were not significantly different between the PDH cases and the controls. In the PDH cases, less GH was secreted in pulses than in the controls, but the difference was not significant. The basal plasma cortisol concentration, the AUC for ACTH and cortisol, and the pulse frequency of ACTH and cortisol decreased significantly after Hypophysectomy for the group of PDH cases. The basal plasma concentrations of ACTH and alpha-MSH, the AUC for alpha-MSH, and the characteristics of the plasma GH profiles of the PDH cases remained unchanged after Hypophysectomy. No pulses of alpha-MSH were observed after Hypophysectomy. The co-occurrence between the ACTH and cortisol pulses decreased significantly with Hypophysectomy. The postoperative pulse frequency of ACTH was the only characteristic with predictive value for the recurrence of PDH after Hypophysectomy. The results of this study demonstrate that ACTH, cortisol, alpha-MSH, and GH are secreted in a pulsatile fashion in dogs with PDH. Hypophysectomy effectively reduces the secretion of ACTH and cortisol. The presence of ACTH pulses after Hypophysectomy is a risk factor for the recurrence of hyperadrenocorticism.
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efficacy of transsphenoidal Hypophysectomy in treatment of dogs with pituitary dependent hyperadrenocorticism
Journal of Veterinary Internal Medicine, 2005Co-Authors: J M Hanson, H S Kooistra, E Teske, Martine M Van T Hoofd, G Voorhout, B P MeijAbstract:The long-term survival, disease-free fractions, and the complications of Hypophysectomy in 150 dogs with pituitary-dependent hyperadrenocorticism (PDH) were examined in a prospective study. Long-term survival and disease-free fractions in relation to pituitary size were analyzed by the Kaplan-Meijer estimate procedure. The 1-, 2-, 3-, and 4-year estimated survival rates were 84% (95% confidence interval [CI], 76-89%), 76% (67-83%), 72% (62-79%), and 68% (55-77%), respectively. Treatment failures included procedure-related mortalities (12 dogs) and incomplete hypophysectomies (9 dogs). The 1-, 2-, 3-, and 4-year estimated relapse-free fractions were 88% (CI: 80-93%), 75% (64-83%), 66% (54-76%), and 58% (45-70%), respectively. Postoperative reduction of tear production (58 eyes in 47 dogs) was often reversible but remained low until death in 11 eyes of 10 dogs. Central diabetes insipidus (CDI) occurred more frequently (62%) in dogs with enlarged pituitaries than in dogs with nonenlarged pituitaries (44%). Survival and disease-free fractions after Hypophysectomy were markedly higher in dogs with nonenlarged pituitaries than in dogs with enlarged pituitaries. Transsphenoidal Hypophysectomy is an effective treatment for PDH in dogs. The survival and disease-free fractions after Hypophysectomy decrease and the incidence of CDI increases with increasing pituitary size. Therefore, early diagnosis of PDH is important and transsphenoidal Hypophysectomy is expected to have the best outcome when used as primary treatment for dogs with nonenlarged or moderately enlarged pituitaries.
J A Mol - One of the best experts on this subject based on the ideXlab platform.
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plasma profiles of adrenocorticotropic hormone cortisol alpha melanocyte stimulating hormone and growth hormone in dogs with pituitary dependent hyperadrenocorticism before and after Hypophysectomy
Journal of Endocrinology, 2006Co-Authors: J M Hanson, H S Kooistra, J A Mol, E Teske, B P MeijAbstract:The 6-h plasma profiles of adrenocorticotropic hormone (ACTH), cortisol, alpha-melanocyte-stimulating hormone (alpha-MSH), and GH were studied in 17 dogs with pituitary-dependent hyperadrenocorticism (PDH) before and after Hypophysectomy. The aim of the study was to investigate the relation between the hormone profile characteristics and recurrence of PDH after surgery. The hormones were secreted in a pulsatile fashion. The basal plasma cortisol concentration and area under the curve (AUC) for cortisol were significantly higher in the PDH cases than in eight controls. The characteristics of the plasma profiles of ACTH and alpha-MSH were not significantly different between the PDH cases and the controls. In the PDH cases, less GH was secreted in pulses than in the controls, but the difference was not significant. The basal plasma cortisol concentration, the AUC for ACTH and cortisol, and the pulse frequency of ACTH and cortisol decreased significantly after Hypophysectomy for the group of PDH cases. The basal plasma concentrations of ACTH and alpha-MSH, the AUC for alpha-MSH, and the characteristics of the plasma GH profiles of the PDH cases remained unchanged after Hypophysectomy. No pulses of alpha-MSH were observed after Hypophysectomy. The co-occurrence between the ACTH and cortisol pulses decreased significantly with Hypophysectomy. The postoperative pulse frequency of ACTH was the only characteristic with predictive value for the recurrence of PDH after Hypophysectomy. The results of this study demonstrate that ACTH, cortisol, alpha-MSH, and GH are secreted in a pulsatile fashion in dogs with PDH. Hypophysectomy effectively reduces the secretion of ACTH and cortisol. The presence of ACTH pulses after Hypophysectomy is a risk factor for the recurrence of hyperadrenocorticism.
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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 pituitary function after transsphenoidal Hypophysectomy in beagle dogs
Domestic Animal Endocrinology, 1997Co-Authors: B P Meij, J A Mol, T S G A M Van Den Ingh, M M Bevers, H A W Hazewinkel, A RijnberkAbstract:Abstract Pituitary function was assessed in healthy adult beagle dogs before and after Hypophysectomy. Anterior pituitary function was tested by use of the combined anterior pituitary (CAP) function test, which consisted of sequential 30-sec intravenous injections of four hypothalamic releasing hormones, in the following order and doses: 1 μg of cortrticotropin-releasing hormone (CRH)/kg, 1 μg of growth hormone-releasing hormone (GHRH)/kg, 10 μg of gonadotropin-releasing hormone (GnRH)/kg, and 10 μg of thyrotropin-releasing hormone (TRH)/kg. Plasma samples were assayed for adrenocorticotropin (ACTH), cortisol, GH, luteinizing hormone (LH), and prolactin (PRL) at multiple times for 120 min after injection. Pars intermedia function was assessed by the α-melanotropin (α-MSH) response to the intravenous injection of the dopamine antagonist haloperidol in a dosage of 0.2 mg/kg. Posterior pituitary function was assessed by the plasma vasopressin (AVP) response to the intravenous infusion of 20% saline. Basal plasma ACTH, cortisol, thyroxine, LH, PRL, and AVP concentrations were significantly lower at 10 wk after Hypophysectomy than before Hypophysectomy. In the CAP test and the haloperidol test, the peaks for the plasma concentrations of ACTH, cortisol, GH, LH, PRL, and α-MSH occurred within 45 min after injection. At 2 and 10 wk after Hypophysectomy, there were no responses of plasma GH, LH, PRL, and α-MSH to stimulation. In four of eight hypophysectomized dogs, there were also no plasma ACTH and cortisol responses, whereas in the other four dogs, plasma ACTH and cortisol responses were significantly attenuated. The basal plasma ACTH and cortisol concentrations were significantly lower in the corticotropic nonresponders than in the responders. Plasma AVP responses were completely abolished by Hypophysectomy, although water intake by the dogs was normal. Histopathological examinations at 10 wk after Hypophysectomy revealed that adrenocortical atrophy was much more pronounced in the corticotropic nonresponders than in the responders. No residual pituitary tissue was found along the ventral hypothalamic diencephalon. However, in all hypophysectomized dogs that were investigated, islets of pituitary cells were found embedded in fibrous tissue in the sella turcica. A significant positive correlation was found between the number of ACTH-immunopositive cells and the ACTH increment in the CAP test at 10 wk after Hypophysectomy. It is concluded that 1) stimulation of the anterior pituitary with multiple hypophysiotropic hormones, stimulation of the pars intermedia with a dopamine antagonist, and stimulation of the neurohypophysis with hypertonic saline do not cause side effects that would prohibit routine use, 2) in the routine stimulation of the anterior pituitary and the pars intermedia, blood sampling can be confined to the first 45 min, 3) the ACTH and cortisol responses to hypophysiotropic stimulation are the most sensitive indicators for residual pituitary function after Hypophysectomy, 4) small islets of pituitary cells in the sella turcica, containing corticotropic cells, are the most likely source of the attenuated corticotropic response that may occur after Hypophysectomy, and 5) residual AVP release from the hypothalamus after Hypophysectomy is sufficient to prevent diabetes insipidus, despite the fact that the AVP response to hypertonic saline infusion is completely abolished.
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 pituitary function after transsphenoidal Hypophysectomy in beagle dogs
Domestic Animal Endocrinology, 1997Co-Authors: B P Meij, J A Mol, T S G A M Van Den Ingh, M M Bevers, H A W Hazewinkel, A RijnberkAbstract:Abstract Pituitary function was assessed in healthy adult beagle dogs before and after Hypophysectomy. Anterior pituitary function was tested by use of the combined anterior pituitary (CAP) function test, which consisted of sequential 30-sec intravenous injections of four hypothalamic releasing hormones, in the following order and doses: 1 μg of cortrticotropin-releasing hormone (CRH)/kg, 1 μg of growth hormone-releasing hormone (GHRH)/kg, 10 μg of gonadotropin-releasing hormone (GnRH)/kg, and 10 μg of thyrotropin-releasing hormone (TRH)/kg. Plasma samples were assayed for adrenocorticotropin (ACTH), cortisol, GH, luteinizing hormone (LH), and prolactin (PRL) at multiple times for 120 min after injection. Pars intermedia function was assessed by the α-melanotropin (α-MSH) response to the intravenous injection of the dopamine antagonist haloperidol in a dosage of 0.2 mg/kg. Posterior pituitary function was assessed by the plasma vasopressin (AVP) response to the intravenous infusion of 20% saline. Basal plasma ACTH, cortisol, thyroxine, LH, PRL, and AVP concentrations were significantly lower at 10 wk after Hypophysectomy than before Hypophysectomy. In the CAP test and the haloperidol test, the peaks for the plasma concentrations of ACTH, cortisol, GH, LH, PRL, and α-MSH occurred within 45 min after injection. At 2 and 10 wk after Hypophysectomy, there were no responses of plasma GH, LH, PRL, and α-MSH to stimulation. In four of eight hypophysectomized dogs, there were also no plasma ACTH and cortisol responses, whereas in the other four dogs, plasma ACTH and cortisol responses were significantly attenuated. The basal plasma ACTH and cortisol concentrations were significantly lower in the corticotropic nonresponders than in the responders. Plasma AVP responses were completely abolished by Hypophysectomy, although water intake by the dogs was normal. Histopathological examinations at 10 wk after Hypophysectomy revealed that adrenocortical atrophy was much more pronounced in the corticotropic nonresponders than in the responders. No residual pituitary tissue was found along the ventral hypothalamic diencephalon. However, in all hypophysectomized dogs that were investigated, islets of pituitary cells were found embedded in fibrous tissue in the sella turcica. A significant positive correlation was found between the number of ACTH-immunopositive cells and the ACTH increment in the CAP test at 10 wk after Hypophysectomy. It is concluded that 1) stimulation of the anterior pituitary with multiple hypophysiotropic hormones, stimulation of the pars intermedia with a dopamine antagonist, and stimulation of the neurohypophysis with hypertonic saline do not cause side effects that would prohibit routine use, 2) in the routine stimulation of the anterior pituitary and the pars intermedia, blood sampling can be confined to the first 45 min, 3) the ACTH and cortisol responses to hypophysiotropic stimulation are the most sensitive indicators for residual pituitary function after Hypophysectomy, 4) small islets of pituitary cells in the sella turcica, containing corticotropic cells, are the most likely source of the attenuated corticotropic response that may occur after Hypophysectomy, and 5) residual AVP release from the hypothalamus after Hypophysectomy is sufficient to prevent diabetes insipidus, despite the fact that the AVP response to hypertonic saline infusion is completely abolished.