Ectopic pituitary adenoma in the sphenoid causing Nelson's syndrome

An ectopic functioning pituitary in the sphenoid is an extremely rare occurrence, and even rarer is pituitary adenoma causing symptoms of Nelson's syndrome. A case is presented of a young female diagnosed and treated in our clinic. The only functioning hypophyseal tissue was detected inside the sphenoid, as the pituitary gland had been radiated because of Cushing's syndrome 10 years before and imaging studies revealed an empty sella.

Gonadotropin-releasing hormone and pituitary adenylate cyclase-activating polypeptide affect levels of cyclic adenosine 3',5'-monophosphate-dependent protein kinase A (PKA) subunits in the clonal gonadotrope alphaT3-1 cells: evidence for cross-talk between PKA and protein kinase C pathways

We have shown previously that protein kinase A (PKA) subunit levels are regulated by activation of PKA or protein kinase C (PKC) in anterior pituitary cells. GnRH also influenced PKA subunit levels, suggesting that hormonal regulation occurs in gonadotrophs, and therefore, we have reexamined this question using the clonal gonadotrope-derived cell line (alphaT3-1 cells). Western blot analysis, using specific immunoaffinity purified immunoglobulins, revealed expression of catalytic (Cat) and regulatory type I (RI) and type II (RII) subunits of PKA in these cells. Activation of adenylyl cyclase (AC) with forskolin, or of PKC with tetradecanoyl phorbol acetate (TPA), caused a rapid (detectable at 0.5-1 h) and concentration-dependent loss of all PKA subunits. Forskolin (10-100 microM) reduced Cat and RI by 60% and RII by 30%, whereas TPA (0.1-1 microM) reduced Cat and RII by 50% and RI by 40%. Simultaneous activation of PKA and PKC caused the expected dose-dependent reductions in Cat, and the effects of forskolin or TPA were nearly additive. RI and RII were reduced similarly by 10 nM TPA, whereas 100 nM TPA tended to prevent the reduction of RI or RII caused by forskolin. GnRH, which activates phosphoinositidase C and not AC in these cells, caused a clear loss of Cat or RII at all concentrations tested and of RI at 0.1 nM. Pituitary adenylate cyclase-activating polypeptide 38, which acts via PVR-1 receptors to stimulate both phosphoinositidase C and AC in these cells, also caused a clear dose-dependent decrease in Cat, RI, and RII, although higher concentrations were needed for the latter effects. Together, the data demonstrate that catalytic and regulatory subunits of PKA are subject to both hormonal and receptor-independent regulation in alphaT3-1 cells, reinforcing the possibility that such effects occur in nonimmortalized gonadotropes. Whereas the effects of PKA activators very likely involve proteolytic degradation of the dissociated PKA holoenzyme, the effects of TPA and GnRH occur in the absence of cAMP elevation by unknown mechanisms. Whatever the mechanisms involved, the data reveal a mechanism for cross-talk between phosphoinositidase C and AC-mediated hormonal signals, in which PKC activation seems to play a pivotal role.

Isolation and characterization of the rat corticotropin-releasing hormone (CRH)-binding protein gene: transcriptional regulation by cyclic adenosine monophosphate and CRH

The CRH-binding protein (CRH-BP) antagonizes the ACTH-releasing activity of the neuropeptide CRH in vitro. However, the function of CRH-BP in vivo and the molecular mechanisms that regulate CRH-BP expression are not well understood. In this study, the rat CRH-BP gene was characterized, and CRH-BP promoter sequences were identified. The rat CRH-BP gene spans almost 12 kilobases and contains 7 exons. Ribonuclease protection experiments indicate that transcription of the CRH-BP gene initiates at multiple sites in rat cerebral cortex. Transfection experiments with CRH-BP-reporter constructs, containing 88-3500 bp 5' flanking and 66 bp 5' untranslated DNA from the rat CRH-BP gene, demonstrate basal promoter activity in multiple cell lines. CRH-BP-reporter constructs also demonstrate positive regulation of promoter activity by cAMP in a variety of cell lines and by CRH in cells expressing the CRH receptor. The DNA sequences between -341 and -88 bp, including the cAMP response element-like sequence at -127 bp, are required for maximal cAMP and CRH regulation of CRH-BP promoter activity. These studies suggest that CRH-BP transcription in vivo may be positively regulated by cAMP and CRH.

Lactation associated with acidophilic pituitary adenoma, pheochromocytoma, and cystic endometrial hyperplasia in two goats

Two unbred adult female goats were examined for persistent, inappropriate lactation. Prostaglandin F2 alpha treatment was ineffective in relieving the condition. Over 5 months, 1 goat developed evidence of CNS disease; this same goat had persistently high serum prolactin concentrations. At necropsy, both goats had an acidophilic adenoma of the pars distalis, a condition that, to our knowledge, has not previously been reported in goats. In addition, both goats had pheochromocytomas and cystic endometrial hyperplasia, conditions that are rarely reported in small ruminants. The inciting cause of inappropriate lactation in goats can be difficult to determine. Pituitary adenomas should be suspected when treatment with prostaglandins is unsuccessful, signs of CNS disease develop, or persistently high serum prolactin concentrations are detected.

Lymphocytic adenohypophysitis and lymphocytic infundibuloneurohypophysitis

One hundred and twenty-four cases of lymphocytic adenohypophysitis have been reported since 1962. Nearly 60% of the cases in women involved inset of the disease in relation to pregnancy. Headache and visual field defects were the most frequent symptoms. Most patients showed signs of either isolated or multiple anterior pituitary hormone deficiency. ACTH secretion was impaired the most frequently, followed by TSH, gonadotropins, GH and PRL secretion. One third of the cases involved hyperprolactinemia. Tissue from patients with lymphocytic infundibuloneurohypophysitis, also suffering from DI, revealed lymphocytic inflammation limited to the infundibulum, stalk, and neurohypophysis. Twenty of these 124 lymphocytic adenohypophysitis patients developed DI before treatment, and neuroimaging studies revealed thickening of the pituitary stalk in some. At least in a few cases, chronic lymphocytic infiltration occurred in both the infundibuloneurohypophysitis and adenohypophysis. Although both lymphocytic adenohypophysitis and infundibuloneurohypophysitis may be caused by autoimmune disorders, the antigens involved may differ.

Interleukin-2 (IL-2) and IL-6 regulate c-fos protooncogene expression in human pituitary adenoma explants

We have previously shown that interleukin-2 (IL-2) and IL-6, which are expressed in the anterior pituitary, affect anterior pituitary cell proliferation in normal rats and cell lines. Here we examined their effects on the c-fos expression by human anterior pituitary adenomas. Adenoma cells in culture do not express c-fos mRNA. In adenoma explants, however, c-fos expression was detected and was regulated by IL-2 or IL-6. In different tumors (ACTH-, PRL-, GH-secreting and non functioning adenomas), these interleukins had inhibitory or stimulatory effects but the kind of response does not seem to be associated to tumor type or size. Using blocking antibodies, we observed that intrinsic IL-2 and IL-6 regulate c-fos expression in the same way. Our data suggest that IL-2 and IL-6 are not only involved in the regulation of pituitary adenoma function but may also, given the role of c-fos in cell proliferation, be implicated in the development of human pituitary adenomas.

The World Health Organization classification of adenohypophysial neoplasms. A proposed five-tier scheme

BACKGROUND

Although numerous attempts have been made, the classification of pituitary neoplasms remains controversial.

METHODS

The present proposal is based on correlative clinical and pathologic (histologic, immunocytochemical, and electron microscopic) studies of more than 8000 surgically removed human pituitary tumors.

RESULTS

Anterior pituitary tumors have been variously classified on the basis of their clinical presentation, biochemical findings, histology (growth pattern, tinctorial characteristics), proliferation indices, immunocytochemical profile, and ultrastructural features. Herein we propose a five-tier classification, clinicopathologic in nature, which focuses on endocrine activity, imaging, operative findings, histology, immunocytochemistry, and ultrastructure. The integration of these five complementary approaches into what is fundamentally a pathologic classification is as practical as it is novel. Its importance lies in the fact that the collected data provide valuable information to the clinical endocrinologist, neurosurgeon, and oncologist involved in the assessment of a tumor's biologic behavior, growth potential, therapeutic responsiveness, and prognosis. Due to financial restraints, lack of facilities, and unavailability of well trained personnel, we realize that at present the five approaches cannot be fully implemented in all institutions. Nonetheless, clinical and biochemical data, imaging, and operative findings, as well as basic histologic parameters are generally readily available. Collectively they are indispensable in establishing the correct diagnosis and in directing patient management. Conversely, the cost-effectiveness of immunocytochemistry and electron microscopy is debatable in that their performance and interpretation requires time, financial resources, and expertise. Nonetheless, it should be clear that any correlation between endocrine activity, growth potential, morphologic features, immunocytochemical profile, and ultrastructural features provides greater insight into the pathobiology of adenohypophysial tumors than is gained by routine histology alone. Thus we feel justified in including immunocytochemical and ultrastructural investigation of pituitary tumors in a modern classification. At present, more sophisticated molecular biologic methods represent investigative tools that play no significant role in the classification.

CONCLUSIONS

A five-tier classification of adenohypophysial neoplasms based on clinical and biochemical results, imaging, operative findings, histology, immunocytochemistry, and electron microscopy is proposed. It is recommended to the World Health Organization for acceptance.

Loss of heterozygosity studies at the retinoblastoma and breast cancer susceptibility (BRCA2) loci in pituitary, parathyroid, pancreatic and carcinoid tumours

OBJECTIVE

Allelic deletion of the retinoblastoma (Rb) gene on chromosome 13 has been reported in both pituitary and parathyroid tumours. We have investigated the roles of the Rb and the hereditary breast cancer susceptibility gene (BRCA2), which lie within 25 cM of each other on chromosome 13q12-14, in the multi-step aetiology of endocrine tumours.

PATIENTS AND MEASUREMENTS

Seventy-seven endocrine tumours (43 anterior pituitary, 22 parathyroid, 7 carcinoid, and 5 pancreatic islet cell tumours) with paired leucocytes have been examined for loss of heterozygosity (LOH) at the Rb and BRCA2 loci by using specific oligonucleotide primers for the PCR amplification of microsatellite polymorphisms at three intragenic Rb markers, Rb1.20, Rbi4 and D13S153, and D13S260 which is linked to the BRCA2 locus.

RESULTS

Seventy-five of the 77 tumour-leucocyte pairs were informative and LOH was detected in 1 of 16 non-functioning pituitary tumours, 1 of 8 prolactinomas, 3 of 19 parathyroid adenomas and 1 of 1 parathyroid carcinoma. All the 3 parathyroid adenomas with LOH were associated with aggressive clinical and histopathological features. Allele loss was not detected in any of the 16 somatotrophinomas, 2 corticotrophinomas, 1 gonadotrophinoma, 7 carcinoid tumours (6 bronchial, 1 metastatic intestinal) or 5 pancreatic islet cell tumours that were informative.

CONCLUSIONS

These results demonstrate that allelic deletions of the 13q12-14 region occur in some pituitary adenomas and 16% of parathyroid adenomas. The extensive loss, which involves both the Rb gene and the BRCA2 locus, suggests that tumour suppressor genes in this region other than Rb or BRCA2 may be involved in the development and progression of some endocrine tumours.

Cytokine expression in human anterior pituitary adenomas

OBJECTIVE

There is increasing evidence for the role of cytokines in pituitary differentiated function and tumorigenesis, but the spectrum of cytokines found in the pituitary is unknown. Therefore profiles of cytokine expression were determined in different human anterior pituitary adenoma sub-types.

DESIGN

The reverse transcriptase-linked polymerase chain reaction (PCR) was used to identify the presence of cytokine mRNA within human pituitary adenomas.

PATIENTS

Seventeen pituitary adenoma biopsies removed at transsphenoidal surgery were examined: 4 somatotrophinomas, 7 non-functional adenomas, 4 prolactinomas, one case of Cushing's disease and one case of Nelson's syndrome.

MEASUREMENTS

RNA was extracted from each adenoma biopsy and reverse transcribed into cDNA. This was specifically amplified in a PCR using oligonucleotide primers complementary to each cytokine. The cytokines investigated were interleukin (IL)-I alpha, IL-I beta, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, tumour necrosis factor (TNF)-alpha, TNF-beta and transforming growth factor (TGF)-beta 1, beta 2 and beta 3. The products of each PCR were visualized using agarose gel electrophoresis.

RESULTS

All 17 adenomas expressed IL-8 transcripts, but no expression of IL-2, IL-5 or IL-7 was found. IL-6 was expressed in all 4 somatotrophinomas, 3 of 7 non-functional tumours, 2 of 4 prolactinomas and in the single case of Nelson's syndrome. At least one of the 3 isoforms of TGF-beta was found in all but 2 tumours; one prolactinoma and one non-functional adenoma. IL-1 alpha, IL-beta, IL-4, TNF-alpha and TNF-beta were expressed sporadically by individual adenomas.

CONCLUSION

These data suggest that whilst IL-8 may be important, the local expression of the cytokines IL-2, IL-5 and IL-7 is not important in human anterior pituitary tumorigenesis.

Galanin gene expression in radiothyroidectomy-induced thyrotroph adenomas

Galanin gene expression is markedly increased in the anterior pituitary glands of estrogen-treated rats (lactotroph hyperplasia) as well as human growth hormone-releasing hormone transgenic mice (somatotroph hyperplasia). The objective of this study was to examine galanin in a mouse model of thyrotroph adenoma formation. Male mice were radiothyroidectomized by use of iodine-131 (131I), and galanin peptide levels were assessed in the hypothalamic-pituitary axis. Immunoreactive galanin concentrations in the anterior pituitaries of 131I-treated mice were decreased 80% at 3, 6, 9, and 12 mo after radiothyroidectomy. Galanin peptide levels in the hypothalamus were decreased 20-25% at these times. Treatment with either estradiol or 3,3',5-triiodo-L-thyronine increased galanin peptide concentrations in the anterior pituitaries of 131I-treated mice, but neither treatment restored galanin concentrations. Galanin mRNA levels were decreased > 80% 1 yr after radiothyroidectomy. We conclude that, unlike animal models of lactotroph and somatotroph hyperplasia, galanin gene expression is suppressed throughout the development of thyrotroph adenomas, suggesting that galanin does not have a stimulatory role in the proliferation of thyrotrophs. Moreover, these data show that thyroid hormones are important positive regulators of galanin gene expression in the mouse and that estrogen may stimulate galanin gene expression in the absence of thyroid hormones.

[Lymphocytic hypophysitis: a reality]

Lymphocytic hypophysitis is a rare entity; we report here three cases. This condition usually occurs in women during pregnancy or in the post-partum period. Pituitary enlargement is associated with complete or partial hypopituitarism. The difficulty in diagnosis is well illustrated by our cases and results from the similarity between the clinical and biological signs of adenoma and hypophysitis. Circulating antipituitary antibodies are not constantly found and are nonspecific, evidence only of the autoimmune nature of hypophysitis. Thus the diagnosis has to be undertaken in all suspected cases in pregnant women or during the post-partum period. The clinical course may be very long, emphasizing the need for rigorous long-term observation. The pituitary gland is commonly enlarged and homogenous in lymphocytic hypophysitis, but in our third case the enlargement was heterogeneous with associated cyst formation. We suggest that the inflammatory process could have been maintained by the presence of cysts. Finally, corticosteroids are the therapy of choice in the inflammatory stage and should be undertaken as soon as the diagnosis has been established. Regular surveillance is required.

Glucocorticoids block protein kinase A inhibition of calcium-activated potassium channels

Adrenal corticosteroids have well known and profound effects on neurons and neuroendocrine cells, but the underlying cellular mechanisms are poorly understood. The present study analyzed membrane currents and ACTH release in AtT20 mouse pituitary corticotrope tumor cells. Patch-clamp analysis revealed a significant and selective inhibition of calcium-activated (BK-type) potassium channels upon activation of protein kinase A by corticotropin-releasing factor or 8-chlorophenylthio-cAMP. The synthetic glucocorticoid dexamethasone had no effect on potassium currents evoked by depolarization but prevented the inhibitory effect of protein kinase A activators. The action of dexamethasone had the hallmarks of protein induction, i.e. a lag time and sensitivity to inhibitors of DNA transcription and mRNA translation. In parallel, the specific BK channel blocker iberiotoxin abolished early glucocorticoid inhibition of corticotropin-releasing factor-stimulated ACTH secretion. In summary, the present data show that glucocorticoid-induced proteins render BK-type channels resistant to inhibition by protein kinase A and that this action of the steroid is pivotal for its early inhibitory effect on the secretion of ACTH.

Calcineurin feedback inhibition of agonist-evoked cAMP formation

The effects of immunosuppressant blockers of calcineurin (protein phosphatase 2B) on cAMP formation and hormone release were investigated in mouse pituitary tumor (AtT20) cells. Immunosuppressants enhanced corticotropin-releasing factor- and isoproterenol-evoked cAMP production in proportion with their potency to block calcineurin. Further analysis of cAMP production revealed that intracellular Ca2+ derived through voltage-regulated calcium channels reduces cAMP formation induced by corticotropin releasing-factor or beta 2-adrenergic stimulation and that this effect of Ca2+ is inhibited by blockers of calcineurin. AtT20 cells were found to express at least three species of adenylyl cyclase mRNA-encoding types 1 and 6 as well as a novel isotype, which appeared to be the predominant species. In two cell lines expressing very low or undetectable levels of the novel cyclase mRNA (NCB20 and HEK293 cells respectively), corticotropin-releasing factor-induced cAMP formation was not altered upon blockage of calcineurin activity. These data identify calcineurin as a Ca2+ sensor that mediates the negative feedback effect of intracellular Ca2+ on receptor-stimulated cAMP production. Furthermore, the effect of calcineurin on cAMP synthesis appears to be associated with the expression of a novel adenylyl cyclase isotype, which is highly abundant in AtT20 cells.

Severe hypotension and coma secondary to unrecognized chronic anterior hypophysitis

We report an endocrine emergency of a 52-year-old woman with chronic anterior-pituitary failure of autoimmune origin who developed hypopituitary crisis with coma and severe hypotension provoked by an intercurrent bronchopneumonia. At admission to the ICU hypopituitarism had not been diagnosed and only Hashimoto's thyroiditis with thyroid replacement therapy could be obtained from the patient's history. Although the patient presented with somatic signs suggestive of hypopituitarism, other causes of coma and hypotension had first to be excluded. In the absence of specific treatment the patient died 18 h later with refractory cardiac arrest. Diagnosis of acute decompensated chronic hypophyseal failure must be considered if hypothermia, refractory hypotension and signs of infection without fever are associated with a short stature and the loss of axillary and public hair. Waiting for laboratory confirmation of the diagnosis must not delay immediate life-saving specific glucocorticoid treatment.

Intrasellar neuronal choristoma associated with growth hormone-producing pituitary adenoma containing amyloid deposits

The histological, immunocytochemical, and ultrastructural features of an intrasellar neuronal choristoma associated with pituitary growth hormone (GH)-producing adenoma are reported. Immunohistochemistry studies and electron microscopy examination showed the adenoma cells to be positive for GH but negative for prolactin, and the neurons of the choristoma to have GH-releasing factor (GRF) neurosecretory activity. The adenoma also had many amyloid deposits in its extracellular space immunoreactive to GRF. This is the first report of the tumor containing amyloid deposits.

Differentiating lymphocytic adenohypophysitis from pituitary adenoma in the peripartum patient

Lymphocytic adenohypophysitis (LAH) is an autoimmune disorder of the pituitary gland with a predilection for the peripartum period and often mimics a pituitary adenoma. We sought to define the clinical, endocrinologic and radiographic characteristics differentiating peripartum LAH from pituitary adenoma to enable the use of noninvasive diagnosis and appropriate therapy. From published reports and our own case, the clinical histories and laboratory and radiographic studies of 45 patients fulfilling the diagnosis of peripartum LAH were reviewed. History of infertility or menstrual irregularity, symptomatology, endocrinologic evaluation, diagnostic imaging and associated medical conditions were analyzed. For comparison, 806 patients with pituitary adenoma and pregnancy from published series were evaluated. The spontaneous pregnancy rate in pituitary adenoma patients was 2.4% vs. 100% in LAH patients. Visual disturbances and headaches were significantly more frequent in patients with LAH. Prolactin levels were significantly lower in patients with LAH than in those with pituitary adenomas (34.6 +/- 46.3 [SD] vs. 393.0 +/- 300.4, P < .0001). Abnormalities in thyroid and/or adrenal function were also more common in patients with LAH (57.5% vs. 2.5%, P < .001). There were no distinguishing characteristics on radiographic studies. History and endocrinologic evaluation can differentiate between LAH and pituitary adenoma in the peripartum patient.

Pituitary disorders during pregnancy

A number of morphologic and physiologic changes accompany pregnancy such as an increase in lactotrophs and prolactin production, and a decrease in gonadotropins and GH. The hormonal milieu can affect patients with prolactinomas, especially macroadenomas, to cause an increase in size in a minority of patients. Complications are treated with bromocryptine. Enlargement of GH-secreting tumors with acromegaly may respond to bromocryptine and possibly to octreotide. Pituitary tumors causing Cushing's syndrome may need removal if major complications develop. Hypopituitarism during pregnancy may be the result of lymphocytic hypophysitis or antepartum pituitary necrosis, and in the postpartum period may be because of postpartum hemorrhage and pituitary necrosis. These abnormalities need prompt recognition and hormonal replacement therapy with neurosurgical decompression to avoid serious morbidity and mortality. Posterior pituitary problems in pregnancy usually manifest by diabetes insipidus, with a pregnancy-specific variety resulting from excessive degradation of AVP by placental vasopressinase. The condition is treated with an analogue dDAVP, which is resistant to vasopressinase.

Prosomatostatin processing in pituitary GH3 cells. Identification and secretion of the intact propeptide

Preprosomatostatin (preproSRIF) is a peptide hormone precursor that undergoes tissue-specific processing at either a single set of paired basic residues to yield SRIF-14 or, alternatively, at a monobasic site to produce SRIF-28, an NH2 terminally extended form of SRIF-14. Mammalian preproSRIFs are a family of precursors that are remarkably conserved from rat to humans. In five species, the signal peptide and propeptides are approximately 96% identical; this high degree of sequence identity may be indicative of functional conservation. Since the propeptide is approximately five times larger than SRIF-14, we hypothesized that it would be secreted as a separate polypeptide following proSRIF proteolytic processing. To test this idea, we raised polyclonal antibodies to the entire propeptide to follow its biosynthesis and secretion. Here we demonstrate that in transfected rat anterior pituitary GH3 cells both SRIF-14 and the intact 9.5-kDa propeptide were processed coordinately from proSRIF with identical kinetics. Treatment of the cells with chloroquine, a weak base which inhibits processing to mature SRIF-14, also inhibited the appearance of the 9.5-kDa propeptide. Approximately 40% of the propeptide was targeted to the regulated secretory pathway as determined by its quantitative secretion in response to secretagogues. We also examined the secretion of the SRIF propeptide independently of SRIF-14 by expressing a truncated "propeptide" in which SRIF-14 was deleted. Significantly, the SRIF propeptide was itself efficiently transported through the secretory pathway and secreted into the culture medium. This suggests that the propeptide possesses all the topogenic information necessary for intracellular transport. The coordinate secretion of the intact propeptide with mature SRIF-14 suggests that it might function as a novel bioactive peptide.

Pit-1 binding sites mediate transcriptional responses to cyclic adenosine 3',5'-monophosphate through a mechanism that does not require inducible phosphorylation of Pit-1

The ability of Pit-1 to mediate transcriptional responses to cAMP has been explored. To test the ability of Pit-1 to mediate transcriptional responses to cAMP, an expression vector was prepared for a mutant Pit-1 in which the major sites of phosphorylation by the cAMP-dependent protein kinase were eliminated. Before using the mutant Pit-1 to study transcriptional regulation, we first examined the ability of the protein to be phosphorylated in vivo in response to cAMP. Transfection and in vivo labeling experiments confirmed that the mutant Pit-1 did not support cAMP-inducible phosphorylation. The ability of the wild type or mutant Pit-1 to mediate transcriptional responses to cAMP was assessed in cotransfection experiments using reporter genes containing either the proximal region of the rat PRL gene or seven copies of a Pit-1 binding site placed upstream of a minimal promoter. Surprisingly, the wild type and mutant Pit-1 expression vectors supported similar responses to cAMP. To further assess the ability of Pit-1 to mediate responses to cAMP, a GAL4-Pit-1 fusion gene was prepared. Although a GAL4-cAMP response element binding protein fusion gene was found to permit transcriptional responses to cAMP, the GAL4-Pit-1 gene was unresponsive. These findings demonstrate that although Pit-1 can facilitate the ability of the PRL promoter to respond to cAMP, phosphorylation of Pit-1 is not required for this response. It seems likely that additional factors that interact with Pit-1 binding sites are important for mediating transcriptional responses to cAMP.

A Pit-1 phosphorylation mutant can mediate both basal and induced prolactin and growth hormone promoter activity

The transcription factor Pit-1 has been shown to be important for both the developmental and homeostatic regulation of expression of the PRL and GH genes in pituitary cells. However, little is known about possible covalent modifications in Pit-1 that might mediate its transactivational properties. Previous studies showing that Pit-1 is a phosphorylation substrate for either protein kinase A or C, or their cellular inducers, led us to investigate whether phosphorylation of Pit-1 is required for its function in either basal or induced cellular activity of either the PRL or GH promoters. The transactivational properties of wild type Pit-1 were compared with those of Pit-1(A3), mutated in the three known phosphorylation sites. At saturating levels of Pit-1 expression vectors, activation of transient basal expression in HeLa cells of constructs (-1957)PRL-CAT or (-244)GH-CAT by RSV-Pit-1(A3) was, respectively, about 50% and 65% as strong as by RSV-Pit-1. Hence, phosphorylation at the sites mutated in Pit-1(A3) is not critically required for basal transactivation of either promoter but may modulate this activity. RSV-Pit-1 and RSV-Pit-1(A3) were equally effective in mediating estrogen receptor stimulation of (-1957)PRL-CAT expression in HeLa cells, thus revealing no phosphorylation requirement for the prerequisite for Pit-1 in estrogen receptor action on the PRL estrogen response element.(ABSTRACT TRUNCATED AT 250 WORDS)

The combination of Pit-1 and Pit-1T have a synergistic stimulatory effect on the thyrotropin beta-subunit promoter but not the growth hormone or prolactin promoters

Pit-1 is a pituitary-specific transcription factor with protein expression limited to thyrotrope, somatotrope, and lactotrope cells of the anterior pituitary gland. We have recently described a thyrotrope-specific variant isoform of Pit-1, called Pit-1T, which contains an additional 14 amino acids in the activation domain generated by an alternate 3'-splicing choice. Pit-1T, in the presence of Pit-1, stimulates the thyrotropin beta-subunit (TSH beta) promoter in a thyrotrope-derived cell that lacks all Pit-1 isoform proteins. Three laboratories have identified another Pit-1 splice variant, called Pit-1 beta, which contains an additional 26 amino acids in the activation domain that is generated by a similar 3'-alternate splice choice. Pit-1 beta has been shown to stimulate the GH promoter, but not the PRL or TSH beta promoters. In this report, we evaluate the effect of the three Pit-1 isoforms (Pit-1, Pit-1T, and Pit-1 beta) on the GH, PRL, and TSH beta promoters when introduced into different cell types. The combination of Pit-1 and Pit-1T had a synergistic stimulatory effect on the TSH beta promoter, but not on the PRL or GH promoters in a thyrotrope-derived cell line that lacks all Pit-1 protein isoforms (alpha TSH cells). When added to GH3 cells, which lack only the Pit-1T isoform, Pit-1T selectively stimulated the TSH beta promoter and not the GH or PRL promoters, suggesting that the thyrotrope-specific Pit-1T exhibits a promoter-specific effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Prosomatostatin processing in permeabilized cells. Endoproteolytic cleavage is mediated by a vacuolar ATPase that generates an acidic pH in the trans-Golgi network

To investigate the relationship between prohormone processing and sorting of mature polypeptides into nascent secretory vesicles, we recently developed a permeabilized cell system that supports both these reactions (Xu, H., and Shields, D. (1993) J. Cell Biol. 122, 1169-1184). Rat anterior pituitary GH3 cells expressing high levels of prosomatostatin (proSRIF) were incubated at 20 degrees C; this temperature prevented exit from the trans-Golgi network and inhibited proSRIF processing. Following the 20 degrees C block, the cells were mechanically permeabilized and incubated at 37 degrees C, and proSRIF processing was determined. Cleavage of proSRIF to the mature hormone required ATP hydrolysis and was inhibited by chloroquine, a weak base, or carbonyl cyanide m-chlorophenylhydrazone, a protonophore. This suggested that a proton gradient and/or an acidic pH facilitated by a vacuolar H(+)-ATPase was required for prohormone processing. We have now utilized the permeabilized cell system in conjunction with the antibiotic bafilomycin A1, a specific inhibitor of vacuolar H(+)-ATPases, to elucidate the role of acidic pH in prohormone processing. Here we report that (i) proSRIF processing was inhibited in vivo and in vitro by low concentrations of bafilomycin A1, confirming the involvement of a vacuolar type ATPase in prohormone processing; (ii) the ATP requirement for processing could be circumvented in vitro by incubating permeabilized cells at acidic pH in the presence of protonophores, indicating that an acidic pH rather than a H+ gradient is necessary for processing; and (iii) a pH of between 6 and 6.2 in the trans-Golgi network was optimal for proSRIF cleavage. We also demonstrate that prohormone convertase 2 exhibited temperature-dependent activity in which proSRIF processing was inhibited at 20 degrees C in vitro. This result explains our previous observation that prohormone processing is inhibited when intact cells are incubated at 20 degrees C.

Panhypopituitarism after cavernous sinus thrombosis

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Effect of corticotrophin-releasing hormone administration on growth hormone levels in acromegaly: in vivo and in vitro studies

The ability of CRH to cause a paradoxical response of GH in acromegaly is still under debate. In this study, the effect of CRH administration on GH release was evaluated in a large series of patients with active acromegaly, both in vivo, compared to that of TRH and GnRH, and in vitro. The study was organized as follows. In vivo study: 30 acromegalic patients were submitted to TRH, GnRH, and CRH tests on non-consecutive days: blood samples were collected before and 10, 20, 30, 45, 60, 90, and 120 min after bolus. In nine patients the CRH test was repeated after a 3-month therapy with octreotide and at the dose of 300-600 micrograms sc thrice daily. In vitro study: CRH (10 nmol/l, 100 nmol/l, and 1 mumol/l) was tested on pituitary tumor tissue obtained in eight patients during transsphenoidal adenomectomy and immediately placed in sterile Ca2+ and Mg2+ free buffer phosphate. A paradoxical GH response to TRH (evaluated as a GH increase over 50% of basal values) was recorded in 19 patients (63.3%), whereas 7 patients (23.3%) responded to GnRH and 4 others to CRH (13.3%). TRH administration induced a maximal percent GH increase significantly greater than that induced by GnRH and CRH (p < 0.05). Octreotide caused the normalization of GH and insulin-like growth factor-I levels in all the patients, as well as the disappearance of the GH paradoxical response to CRH in 3/4 patients. All four CRH responders and four CRH non-responders, used as controls, were surgically treated and adenomatous tissue was used for the in vitro study.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduction in size of a thyrotropin-secreting pituitary adenoma treated with octreotide acetate (somatostatin analog)

We present a 55-year-old female with a thyrotropin (TSH)-secreting pituitary adenoma who had been treated with somatostatin analog octreotide acetate (SMS 201-995) for 4 months. Subcutaneous injection of 100 micrograms octreotide acetate twice daily resulted in significant reduction of the TSH, thyroid hormone, and tumor size. During the treatment, there was no evidence of any side effects. We may conclude that octreotide acetate administration is an effective treatment in patients with TSH-secreting pituitary adenoma for suppressing TSH hypersecretion and reducing the size of the tumor.

Comparative 3H-CCK-8S binding studies on CCKB-type receptors in guinea-pig cortex and continuous cell lines

The present study was undertaken to compare binding characteristics of CCKB-type receptors in guinea-pig cortex, Jurkat T-cells, GH3 cells and C6 cells. The rank order of potency of a variety of CCK agonists and antagonists in inhibiting specific [3H]CCK-8S binding was highly correlated for the 4 CCKB receptor models as demonstrated by a computer-assisted statistical analysis. Taking the ligand binding profiles as the criterion it is concluded that CCKB receptors in guinea-pig cortex, Jurkat T-cells, pituitary GH3 cells and rat glioma C6 cells share identical pharmacological properties.

C-type natriuretic peptide stimulates secretion of growth hormone from rat-pituitary-derived GH3 cells via a cyclic-GMP-mediated pathway

Although C-type natriuretic peptide (CNP) has been shown to exist at the highest concentration in the anterior pituitary in rat tissues, its physiological role(s) there is (are) not clear. In this study, we report a novel function of CNP examined with anterior pituitary-derived cell lines, GH3 and AtT20/D16v-F2. Both CNP and atrial natriuretic peptide (ANP) increased cellular cGMP levels in both cell lines in dose-dependent manners. CNP, but not ANP, stimulated growth hormone (GH) release from GH3 cells. In contrast, neither ANP nor CNP had any significant effect on the corticotropin release from AtT20/D16v-F2 cells. An activator for cGMP-dependent protein kinase (cGK), dibutyryl cGMP, mimicked the stimulation of GH release from GH3 cells by CNP. Constitutive GH release from GH3 cells was greatly diminished in the presence of inhibitors for cAMP-dependent protein kinase, while stimulative GH release by CNP was not affected. However, inhibitors which can block cGK almost completely diminished the stimulative effect of CNP. An inhibitor for protein kinase C did not show any effect on either constitutive or CNP-stimulative GH release. Our observations indicate that the stimulation of GH release from GH3 cells by CNP is mediated mainly by the cGK signal-transduction pathway, not by cAMP-dependent protein kinase or protein kinase C, through a CNP-specific receptor (possibly ANP-B receptor). Thus, CNP may act as a local modulator in the anterior pituitary.

Panhypopituitarism caused by solitary parasellar metastasis from lung cancer

Clinical panhypopituitarism caused by cancer with parasellar metastasis and hypothalamic invasion is very rare. This report concerns a lung cancer patient who had solitary parasellar metastasis with diabetes insipidus and panhypopituitarism as an initial manifestation, which was documented by contrast-enhanced computed tomographic scan, Gd-DTPA-enhanced magnetic resonance imaging, and endocrinologic studies.

Incorporation of the pancreatic membrane protein GP-2 into secretory granules in exocrine but not endocrine cells

The pancreatic zymogen granule membrane protein GP-2 was introduced into cells of exocrine or endocrine origin by transfection of its cDNA in order to investigate the mechanisms by which proteins are specifically incorporated into the membranes of secretory granules. Permanent transformants expressing GP-2 were isolated from exocrine pancreatic-derived AR42J cells as well as AtT20 cells of anterior pituitary origin and insulinoma-derived Rin5F cells. In AR42J cells, GP-2 was localized by immunofluorescence and immunoelectron microscopy to the endogenous zymogen-like granules as well as to the plasma membrane. In experiments supporting the localization data, incubation of the AR42J transformants with the secretagogue cholecystokinin (CCK8) resulted in enhanced release of a shed form of GP-2 into the medium in parallel with amylase, suggesting that the two proteins were secreted from the same compartment. By contrast, when expressed in AtT20 cells, the protein was found by immunofluorescence microscopy on the plasma membrane as well as in intracellular vesicles that differed in size and location from the endogenous secretory vesicles. By electron microscopy, large (approximately 0.5 micron) multivesicular structures were observed. Single- and double-label immunoelectron microscopy demonstrated that these large organelles labeled with anti-GP-2 antibodies, whereas the smaller adrenocorticotropic hormone (ACTH)-containing secretory vesicles did not. In permanent transformants of Rin5F cells, GP-2 was also excluded from the insulin-containing granules and found in multivesicular bodies similar to those in the AtT20 cells and containing the endosomal/lysosomal marker endolyn-78. Despite the apparent accumulation of GP-2 in lysosome-like structures, it turned over slowly and did not undergo rapid endocytosis from the cell surface. We conclude that GP-2 is targeted to secretory granule membranes by cell type-specific mechanisms that likely involve its interaction with other membrane or content proteins expressed only in the exocrine cells.

[Treatment of the non-functioning hypophyseal adenoma]

Non-functioning pituitary adenoma is a lesion usually large enough to produce loss of vision and often loss of libido. Transsphenoidal microsurgery is the treatment of choice of these patients. Postoperative radiation therapy should be performed in patients with significant residual pituitary adenoma. Some studies have recently reported that somatostatin analogue may be useful as adjuvant medical therapy, at least in order to improve visual field defects.

Pituitary stalk and ectopic hyperintense T1 signal on magnetic resonance imaging. Implications for anterior pituitary dysfunction

OBJECTIVE

To determine if improved delineation of hypothalamic-pituitary neuroanatomy by magnetic resonance imaging, especially the posterior pituitary hyperintense T1 signal, can be correlated with anterior and posterior pituitary endocrine function.

DESIGN

Children with ectopic posterior pituitary tissue were identified at the Endocrine Clinic of the Children's Hospital of Pittsburgh (Pa) and their records were reviewed.

PARTICIPANTS

Ten children with ectopic posterior pituitary tissue.

MEASUREMENTS

Anterior pituitary hormone status, determined by standard testing, was correlated with the morphologic anomalies of the hypothalamic-pituitary region on magnetic resonance imaging.

RESULTS

Patients were categorized by the appearance of the pituitary stalk based on the magnetic resonance image: attenuation of the stalk (group 1) or nonvisualization of the stalk (group 2). Patients in group 1 retained partial anterior pituitary function. Patients in group 2 had panhypopituitarism.

CONCLUSION

Prospective evaluation of affected individuals may provide insight into the pathophysiologic mechanisms of idiopathic hypopituitarism.

A case of acromegaly identified after patient complaint of apertognathia

Acromegaly results from the over production of growth hormone after the age at which the epiphyses of the bones have fused. The most common cause is an adenoma of the anterior pituitary gland. Early signs and symptoms are subtle and delayed diagnosis is common. The health consequences of untreated acromegaly are considerable. A brief description of the condition is given and a case report is included. The condition of the patient was first diagnosed after a dental examination at which he voiced a complaint of the inability to incise and a progressive open bite that he attributed to prosthetic treatment. On the basis of his intraoral radiograph history, it is probable that he developed the disease more than 5 years before its diagnosis.

[Ultrastructural in situ hybridization on ultrathin sections of frozen tissues]

In situ hybridization on ultrathin frozen sections can be performed with either complementary DNA or synthetic oligonucleotide probes, labeled with 35S or an antigen (biotin or digoxigenin) respectively revealed by ultrastructural autoradiographic and immunocytological techniques. Using this method, GH mRNA was found in somatotrophs, mainly in the cytoplasm (endoplasmic reticulum and cytoplasmic matrix). Ultrastructural deterioration is the main drawback of this method but is more than outweighed by high sensitivity.

[Severe hyponatremia disclosing adenohypophyseal insufficiency with empty sella syndrome]

We report a case of extremely severe hyponatraemia which led to the discovery of anterior hypophysis insufficiency associated with empty sella turcica in a dysimmune context. This type of hyponatraemia is consecutive to corticotropic and thyreo-tropic hormones deficiency and to inappropriate secretion of arginine vasopressin. These endocrine abnormalities are of suprapituitary origin. They can be explained by a hypothalamo-hypophyseal dysregulation of little known mechanism, or by a lesion of the hypothalamus.

Spontaneous neoplasms in aged Sprague-Dawley rats

Incidence of neoplastic lesions in untreated Sprague-Dawley rats (1340 males and 1329 females) used as controls in 17 carcinogenicity studies are tabulated and evaluated. In male rats, the most common neoplasms were benign pheochromocytomas and keratoacanthomas (4.0% in each case) followed by pancreatic islet cell adenomas (3.7%), thyroid parafollicular cell adenomas (3.6%), fibromas and squamous cell papillomas of the skin and hepatocellular adenomas (2.0% in each), malignant lymphoma lymphocytic (1.9%), histiocytic sarcomas (1.4%), and adrenal cortical adenomas (1.2%). In female rats, the most common neoplasms were of mammary gland origin (31.3%: fibroadenoma 19.0%, adenocarcinomas 8.8%, and adenomas 3.5%) followed by thyroid parafollicular cell adenomas (2.9%), uterine endometrial stromal polyps (2.6%), adrenal cortical adenomas (1.9%), malignant lymphoma lymphocytic (1.6%), fibromas in the skin (1.3%), and pancreatic islet cell adenoma (1.1%). Metastases were observed from pheochromocytomas, hepatocellular carcinomas, nephroblastomas, renal pelvis transitional cell carcinoma, interstitial cell tumor and seminoma of the testes, Zymbal's gland adenocarcinomas, and mammary adenocarcinomas.

Cloning and expression of the thyrotropin-releasing hormone receptor from GH3 rat anterior pituitary cells

Functional thyrotropin-releasing hormone (TRH) receptors have been expressed in Xenopus laevis oocytes following the microinjection of total and poly(A)+ RNA from GH3 rat anterior pituitary tumour cells. Under voltage-clamp conditions, application of the peptide induced a biphasic Ca(2+)-dependent chloride current. The amplitude of the initial, fast, component of the response was dependent on the concentration of the hormone and on the amount of mRNA injected. Size fractionation of poly(A)+ RNA on a continuous sucrose gradient and Northern blot analysis indicated that the receptor was encoded by an mRNA of approx. 3.5 kb. A 3.28 kbp cDNA encoding the TRH receptor has been cloned and sequenced. Full functionality of the predicted 412-amino-acid receptor protein was demonstrated by functional expression of cell surface receptors in Xenopus oocytes after both cytoplasmic injection of sense RNA transcribed in vitro from this cDNA and nuclear injection of the cDNA under the control of the Herpes simplex virus thymidine kinase promoter. The predicted protein contains seven putative membrane-spanning domains and shows significant sequence identify with some G-protein-coupled receptors. RNA blot analysis indicates that the mRNA for the TRH receptor is exclusively expressed in the pituitary gland. Expression studies performed with clones in which the 3' region of the mRNA has been successively shortened indicate that the 3' terminal region is not an important determinant for efficient functional expression in oocytes.

[ACTH-independent Cushing's syndrome due to bilateral macronodular adrenal hyperplasia with empty sella turcica and anterior panhypopituitarism]

A case is presented of Cushing's syndrome due to macronodular bilateral adrenal hyperplasia which is ACTH-independent as was demonstrated by the undetectable basal and after stimulation with metoprolol ACTH plasma levels. High cortisol levels is associated in this patient with empty sella turcica and anterior panhypopituitarism with confirm the exclusive adrenal origin of the hormone hypersecretion and the lack of treatment success with hypophysis ablation in this process.

Gonadotropin-releasing hormone-induced accumulation of follicle-stimulating hormone beta-subunit messenger ribonucleic acid in adenohypophysial cells developing in an ectopic position

We investigated the influence of LHRH on the accumulation of FSH beta messenger RNA (mRNA) in anterior pituitary glands removed from hamster pups less than 36 h old and transplanted beneath the renal capsules of adult male hamsters (hosts). Three experiments were performed in which some hosts were injected sc with LHRH (1 microgram/injection) and others were injected with vehicle. Injections were begun in the afternoon of the day of transplantation (day 1) and were given at 0800 and 1700 h for 6 days and at 0800 h on the eighth day. An additional experiment was performed in which adult male hamsters not bearing allografts were injected with the same regimen of LHRH or vehicle. The hamsters were decapitated on the eighth day of the study, 2 h after the last injection. The allografts, adenohypophyses of the hosts, adenohypophyses of hamsters without allografts, and adenohypophyses of normal adult male rats were removed and frozen on dry ice immediately. Additionally, adenohypophyses were collected from hamster pups less than 36 h old and 8 and 15 days of age. Total RNAs from some pooled specimens were electrophoresed on a formaldehyde-agarose gel. After transfer to Nytran, the RNAs were hybridized sequentially to complementary DNAs for rat FSH beta and hamster beta-actin. The rat FSH beta complementary DNA probe hybridized to a single RNA (approximately 1.7 Kb) in rat adenohypophyses. It predominantly hybridized to RNA of approximately 1.7 Kb from hamster adenohypophyses. Sometimes it hybridized to RNAs ranging in size from 0.5 Kb to 1.7 kb. The hybridization signals for all samples obtained from dot blot analyses were quantitated and normalized to the signals for beta-actin. The hybridization signals obtained from adenohypophyses of hamsters of different ages increased from 36 h of age to adulthood. The hybridization signal obtained from adenohypophyses of hamsters less than 36 h old (the same age as the donor hamsters) was similar to the hybridization signal obtained from allografts in vehicle-treated hamsters. The relative levels of FSH beta mRNA in allografts of LHRH-treated hosts were: 1) greater than the relative levels in adenohypophyses of hamsters less than 36 h old (P less than 0.05) and in allografts in vehicle-treated hamsters (P less than 0.05), 2) greater than the relative levels in adenohypophyses of 8-day-old hamsters (P less than 0.05), and 3) not different compared to the relative levels in adenohypophyses of 15-day-old hamsters and adult male hamsters.(ABSTRACT TRUNCATED AT 400 WORDS)