Regulation of Prolactin Secretion in Canine Pituitary-Dependent Hyperadrenocorticism

Stolp, R.; Bevers, M.M.; Rijnberk, A.; Croughs, R. J. M.; Rutteman, Gerard R.

doi:10.1055/s-2007-1012383

Cited by 15 publications

(14 citation statements)

References 10 publications

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“…The limit of detection for LH was 0•31 µg/l and the intraand interassay coefficients of variation were 2•3% and 10•5%, respectively. Plasma PRL was measured in a heterologous RIA (Stolp et al 1986). The limit of detection was 0•8 µg/l plasma.…”

Section: Hormone Determinationmentioning

confidence: 99%

Alterations in anterior pituitary function of dogs with pituitary-dependent hyperadrenocorticism

Meij¹,

Mol²,

Bevers³

et al. 1997

Journal of Endocrinology

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For the purpose of obtaining an integral picture of anterior pituitary function in canine pituitary-dependent hyperadrenocorticism (PDH), 47 dogs with PDH and eight control dogs received combined administration of four hypophysiotropic hormones (CRH, GHRH, GnRH and TRH) and measurements were made of ACTH, cortisol, GH, LH, PRL and TSH. Basal plasma levels in 47 dogs with PDH were higher for ACTH, cortisol and PRL, lower for GH, and not different for LH (n = 25 noncastrated dogs) and TSH compared with controls (n = 8). In dogs with PDH the responses to combined hypophysiotropic stimulation, measured as increment and area under the curve (AUC), were not different for ACTH, lower for GH and TSH (increments and AUC) and higher for cortisol (increments), LH (AUC, n = 25 noncastrated dogs) and PRL (increments and AUC) than in controls. We conclude that pituitary function is altered in several respects in dogs with PDH. 1) In spite of persisting hypercortisolemia and the neoplastic transformation of the corticotropic cells, these cells usually remain responsive to combined hypophysiotropic stimulation. 2) Basal plasma GH concentrations and GH responsiveness in the combined stimulation test are decreased, probably as a result of the glucocorticoid-induced increase in somatostatin tone. 3) Plasma PRL concentrations and the PRL response to stimulation are increased, probably as a result of cosecretion with ACTH by the transformed corticotropic cells. 4) Despite the well known effect of glucocorticoids of decreasing circulating concentrations of gonadal steroids and thyroxine, the basal plasma concentrations of LH and TSH remain unchanged and there is a tendency to hyperresponsiveness to stimulation for LH and hyporesponsiveness for TSH. The most likely explanation for these changes is a dual effect of glucocorticoids: a direct effect on the gonads and thyroids and/or the transport and metabolism of their secretory products, and an influence on the sensitivity of the feedback control at the hypothalamic-pituitary level.

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Section: Hormone Determinationmentioning

confidence: 99%

Alterations in anterior pituitary function of dogs with pituitary-dependent hyperadrenocorticism

Meij¹,

Mol²,

Bevers³

et al. 1997

Journal of Endocrinology

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“…Prolactin concentrations were determined by a previously validated heterologous radioimmunoassay (22). LH concentrations were determined by a heterologous radioimmunoassay as described Calculations and statistical analysis of the data The progesterone release after day 33 was compared with the total progesterone release of the luteal period and defined by measurement with a digital planimeter (Haff; West Germany) of the surface areas limited by the lines of the progesterone level and the Xaxis from day 1 and 33 to the end of the luteal period.…”

Section: Radioimmunoassaysmentioning

confidence: 99%

Evidence for prolactin as the main luteotrophic factor in the cyclic dog

Okkens

Bevers

Dieleman

et al. 1990

Veterinary Quarterly

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SUMMARY The role of prolactin and LH in the control of the function of the corpus luteum in the dog was studied. Experiments were performed to interfere with the secretion of a) prolactin by administering a dopamine agonist and b) LH by desensitisation with a long-acting LHRH and by stimulation. Treatments with prolactin-lowering dosages of bromocriptine, (20 pg/kg body weight twice a day, orally; n = 8) which started between day 1-5 (n = 4) and day 20-24 (n = 4) of the luteal period resulted in a similar pattern of progesterone concentration in peripheral blood in both groups. The progesterone release in the second half of the luteal period (13. I ± 1.8% (sem) of the progesterone release of the total luteal period) was significantly lower than in control dogs (24.7 ± 2.2%). Treatment at about day 30 of the luteal period with LHRH CR (1.34 mg, intramuscularly; n = 3), which significantly suppressed the LH level, did not reduce the progesterone release in the second half of the luteal period, 21.3 ± 4.7% compared to 24.7 ± 2.2% in the control dogs. The endogenous LH peak resulting from treatment with LHRH had no effect on the progesterone concentration in the blood. It is concluded that prolactin is the main luteotrophic factor in the cyclic dog during the second half of the luteal period.

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“…In their study, pituitary responses were evaluated by a combination stimulus of hypothalamic hormones, which showed that the PDH dogs had augmented PRL response clearly higher than normal dogs. Another in vivo study using the dogs with hyperadrenocorticism due to adrenocortical tumors (ATH) also exhibited increased levels of serum PRL [16], although the PRL secretion in the ATH dogs normally responded to exogenous bromocriptine or TRH [16]. Given that amelioration of hypercortisolemia by adrenalectomy has normalized serum PRL levels in our Cushing's case, hypercortisolemia is most likely to be involved in the coexisting hyperprolactinemia.…”

Section: Discussionmentioning

confidence: 75%

Reversible Pituitary Dysfunction in a Patient with Cushing's Syndrome Discovered as Adrenal Incidentaloma

et al. 2004

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Abstract. We report a 45-year-old woman with Cushing's syndrome showing reversible pituitary dysfunction. Left adrenal tumor was incidentally discovered by a screening examination of abdominal computed tomography. Although this patient lacked typical Cushingoid features except hypertension and leg edema, endocrine examinations revealed moderate suppression of plasma ACTH (~6.3 pg/ml) with relatively high levels of serum cortisol (~22.9 mg/dl) without normal circadian rhythm. Plasma ACTH failed to respond to either CRH or metyrapone, and dexamethasone failed to suppress her daily steroid production. Surgical removal of left adrenocortical adenoma and 6-month replacement of hydrocortisone have ameliorated both ACTH and cortisol responses to CRH loading test. Postoperative responses of TSH and GH to TRH and GRH, respectively, were two fold higher than the preoperative levels. In contrast, basal and TRH-induced levels of serum PRL were decreased after surgery although both the basal and stimulated PRL levels were markedly high before surgery. In addition, gonadotropin response to GnRH examined in the same ovarian cycle was decreased in accordance with an increase in serum estradiol and progesterone levels after surgery. Improvement of hypercortisolemia even in a moderate case of Cushing's syndrome not only ameliorates hypertension, obesity and glucose intolerance, but also restores the accompanying dysfunctions of anterior pituitary, suggesting the clinical importance of early discovery and treatment of functioning adrenocortical incidentalomas.

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Regulation of Prolactin Secretion in Canine Pituitary-Dependent Hyperadrenocorticism

Cited by 15 publications

References 10 publications

Alterations in anterior pituitary function of dogs with pituitary-dependent hyperadrenocorticism

Alterations in anterior pituitary function of dogs with pituitary-dependent hyperadrenocorticism

Evidence for prolactin as the main luteotrophic factor in the cyclic dog

Reversible Pituitary Dysfunction in a Patient with Cushing's Syndrome Discovered as Adrenal Incidentaloma

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